Home » Public Forums » GMCnet » Quadrajet Conundrum
Quadrajet Conundrum [message #271272] |
Thu, 05 February 2015 23:27 |
Vince Kirkhuff
Messages: 12 Registered: May 2009
Karma: 0
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Junior Member |
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First, let me apologize for the length of this post... if you don't wish to read my diatribe, I understand; I won't be offended if you choose to simply move on.
My name is Vince Kirkhuff; I have met some of you at some of the Western States Rallies. I've posted here only a handful of times, because I can usually find the answer to any GMC situation by searching the Forum archives. I have not had any luck finding a similar situation to what I am now experiencing.
I live in San Luis Obispo on the Central Coast of California. I drive a 1977 Eleganza II with the 455 and a stock Quadrajet. I've owned it 6-1/2 years bought it from the original owner with 45,000 miles on it. It has about 56,000 on it now.
5 or so years ago I was experiencing classic vapor lock problems: Hot day, at altitude (3,500+ ft.), and starting off from an idle, the engine would stumble and backfire through the carb or die altogether. In an attempt to correct his problem, I installed a Carter P4070 electric fuel pump and inline filter just downstream from the tank selector valve. I used the selector valve as the power source, so the pump only ran when the auxiliary tank was selected. The pump was on a by-pass loop, with a check valve in the main line to keep all the gas moving toward the engine. The mechanical fuel
pump was in its original configuration.
This worked pretty well until one hot day I was trying to climb Greeley Hill Rd. out of Greely Hill, California, which is a fairly long, steep grade, and the fuel gauge was showing about ¼ tank. I was running the electric pump, due to vapor lock conditions, and heading up that hill, all of the gas sloshed to the rear (main) tank. My auxiliary tank was now dry, so I had to switch back to the main tank turning off the pump! The engine would not run at faster than an idle without the pump, but it wouldn't run at all on the (dry) auxiliary tank. I had to back down this narrow, twisting, two-lane country road about a quarter of a mile to where I could turn around. Luckily, I was able to nurse it the ½ mile or so back into town where there was a gas station.
So, my next modification was to hook up the electric pump to run all the time. I was happy to get rid of the bypass circuit with the T's, the check valve, and about 10 hose clamps, I figure my potential for leaks was drastically reduced. I was now running both the electric and mechanical pumps full time. It was with this set up that the Mysterious Lean Condition first manifested.
The first time I felt it do this, I was heading up Highway 5 me, the wife, the mother-in-law, and 3 dogs; on our way to a family camp out. About 2 hours into our trip and this was nighttime it starts to feel like it's running out of gas; but I've still got at least ½ a tank, according to the gauge. But I think I'm feeling it hesitate... then falter, then finally backfire through the carb... this takes about 10 minutes, and 10 miles driving down the road. The more gas I give it, the worse it runs opening the throttle is just leaning it out. The engine finally dies and we coast to a stop on the shoulder of the freeway.
So we sit there a minute, and I'm trying to think of what to do... diagnose my fuel problem? Am I going to repair it? On the side of Hwy 5? In the dark? Call a tow truck? I'm thinking, if we weren't on the shoulder of the freeway, we could just go to bed and worry about it in the morning. So then I'm thinking, if I can get it running, at least I can maybe get it off the freeway. So I crank the engine, and it fires right up, and it runs fine, and we accelerate into traffic just like nothing... it's getting plenty of gas; the secondaries are clearly working, and it runs great! In 10 minutes, it does it again. Wait a couple of minutes, start it up, and off we go again. I finally figured out I could keep it running if I went a lot slower like under 55 m.p.h. It seemed like it had enough fuel to maintain that speed, but no faster. We found a campground for the night.
In the morning, I called Kanomata's shop and talked to Nick, and he said yeah, it sounds like a lean fuel issue, and suggested a fuel filter. So I bought one and replaced it when we got to our destination. We were there for 2 nights, and then headed home. Out on the road it ran fine, so I thought I had fixed it. Then, a couple of hours into the drive, it started doing it again. We had a slow drive home that day, just taking it easy in the slow lane. That was a year and a half ago.
Since then, we've only had it out on long enough drives to create the problem twice. (A lot of our trips are within an hour or so of home, and it always runs fine for the first 90 minutes, at least.) I thought maybe something weird was happening between the 2 fuel pumps, so I have bypassed the mechanical pump. I also removed the fuel filter at the carb, and replaced the ignition module for good measure. It still does it after those changes. It will do it with a nearly full tank of gas, a part tank, or nearly empty main tank or auxiliary. The last time it did it, I got a big clue: when it started to feel like it was running out of gas, I pumped the gas pedal like mad, and it ran better. So this makes me think the carb is getting fuel there's obviously fuel in the float bowl, but for some reason it's running lean, and the accelerator pump enriches it enough so it runs okay. I was able to nurse it along for about 10 miles down the freeway by pumping it to help it up little hills and such; but still, it eventually died. Again: Wait 1 or 2 minutes, and it starts and runs fine.
Before I took it out on that last road trip, I searched the Forum archives for similar problems, but didn't find one exactly like mine... in that my problem fixes itself with a few minutes' rest. Thinking it may be electrical, I contacted Dick Patterson, who thought it sounded like a fuel problem and promptly talked me out of buying a distributor from him. It was his suggestion to remove the fuel filter at the carb, and check all the primary coil connections as well as the ignition module connections. I also installed a temporary pilot light to tell me if the fuel pump has power (it does). The tanks were dropped 4 years ago (very clean at that time) and new rubber lines were installed.
I read one story on the interweb of some guy with a Camaro or a Chevelle with a similar sounding problem, and he found it to be a problem with the power piston in the Q-jet something about a little plastic clip that holds the top of it, and it had broken and was getting in there sideways but I don't know enough about carburetors to know if that experience is applicable to my situation. I'm hoping that one of you all has maybe run into this same situation and knows just the thing to fix it.
Alternatively, of course, is that many of you are knowledgeable about all things Rochester (or all things GMC), and even if you haven't seen this manifestation, perhaps these symptoms are pointing to some particular part? Any help is appreciated!
Vince Kirkhuff
1977 Eleganza II
San Luis Obispo, CA
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Re: Quadrajet Conundrum [message #271276 is a reply to message #271272] |
Fri, 06 February 2015 00:11 |
Bullitthead
Messages: 1411 Registered: November 2013
Karma: 5
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Senior Member |
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Sounds like a blockage in the main metering jets. That's why it still runs when you pump the gas. Had the problem back in my high school years on the 6 cylinder Falcon I was driving. Just ran out of power going down the road, but it idled fine when I stopped. Had to creep along in first gear on the shoulder for about a mile to the next intersection. Couldn't be the fuel filter, I had just replaced that the day before! Took the carb apart at the gas station and found that my replacement technique had scraped the inside of the fuel hose and a tiny speck of rubber hose was sitting in the main jet. Still had to remove the carb completely, turn it upside down, and use a drinking straw and lung power to get it out of there because I didn't have a screwdriver in my tool box with a wide enough blade to remove the jet.
The Quadrajet is a good combination carb for power and economy, but it does not tolerate any dirt in the system, and there are ways for stuff to get into the carb besides the fuel line. Like the vent tube. Take the air horn off and check it out. You can do it on the engine, like I did at 4 in the morning on the Firebird at the Holiday RV park in Va. Beach in 1979.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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Re: Quadrajet Conundrum [message #271277 is a reply to message #271276] |
Fri, 06 February 2015 00:19 |
Bullitthead
Messages: 1411 Registered: November 2013
Karma: 5
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Senior Member |
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Incidentally, Pismo Beach is the destination for our GMC when we take our first real road trip. Would like to make it for the RV show in March, but I don't know if all the factors are going to line up for that. Might try to look you up if/when we get there.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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Re: [GMCnet] Quadrajet Conundrum [message #271278 is a reply to message #271276] |
Fri, 06 February 2015 00:30 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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Senior Member |
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Had a teasel seed in the main jet of a jikov carb on a CZ 250cc 2 stroke
dirt bike that defied compressed air. It only blocked the jet when the
slide needle was fully pulled up. Engine would run at part throttle, but
not at wfo. Drove me nuts for a couple of days until I dislodged it with a
dental pic under a magnifying lens. Close inspection revealed the seed had
tiny barbs like a bee stinger. It would just defy being blown out with air.
Strange "stuff" happens sometimes.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Feb 5, 2015 10:11 PM, "Terry" wrote:
> Sounds like a blockage in the main metering jets. That's why it still runs
> when you pump the gas. Had the problem back in my high school years on the
> 6 cylinder Falcon I was driving. Just ran out of power going down the
> road, but it idled fine when I stopped. Had to creep along in first gear on
> the
> shoulder for about a mile to the next intersection. Couldn't be the fuel
> filter, I had just replaced that the day before! Took the carb apart at the
> gas station and found that my replacement technique had scraped the inside
> of the fuel hose and a tiny speck of rubber hose was sitting in the main
> jet. Still had to remove the carb completely, turn it upside down, and use
> a drinking straw and lung power to get it out of there because I didn't
> have a screwdriver in my tool box with a wide enough blade to remove the
> jet.
>
> The Quadrajet is a good combination carb for power and economy, but it
> does not tolerate any dirt in the system, and there are ways for stuff to
> get
> into the carb besides the fuel line. Like the vent tube. Take the air horn
> off and check it out. You can do it on the engine, like I did at 4 in the
> morning on the Firebird at the Holiday RV park in Va. Beach in 1979.
> --
> Terry Kelpien
> ASE Master Technician
> 73 Glacier 260
> Smithfield, Va.
> _______________________________________________
> GMCnet mailing list
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>
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Re: Quadrajet Conundrum [message #271280 is a reply to message #271272] |
Fri, 06 February 2015 02:17 |
George Beckman
Messages: 1085 Registered: October 2008 Location: Colfax, CA
Karma: 11
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Senior Member |
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Vince Kirkhuff wrote on Thu, 05 February 2015 21:27First, let me apologize for the length of this post... if you don't wish to read my diatribe, I understand; I won't be offended if you choose to simply move on.
My name is Vince Kirkhuff; I have met some of you at some of the Western States Rallies. I've posted here only a handful of times, because I can usually find the answer to any GMC situation by searching the Forum archives. I have not had any luck finding a similar situation to what I am now experiencing.
I live in San Luis Obispo on the Central Coast of California. I drive a 1977 Eleganza II with the 455 and a stock Quadrajet. I've owned it 6-1/2 years bought it from the original owner with 45,000 miles on it. It has about 56,000 on it now.
So, my next modification was to hook up the electric pump to run all the time. I was happy to get rid of the bypass circuit with the T's, the check valve, and about 10 hose clamps, I figure my potential for leaks was drastically reduced. I was now running both the electric and mechanical pumps full time. It was with this set up that the Mysterious Lean Condition first manifested.
So we sit there a minute, and I'm trying to think of what to do... diagnose my fuel problem? Am I going to repair it? On the side of Hwy 5? In the dark? Call a tow truck? I'm thinking, if we weren't on the shoulder of the freeway, we could just go to bed and worry about it in the morning. So then I'm thinking, if I can get it running, at least I can maybe get it off the freeway. So I crank the engine, and it fires right up, and it runs fine, and we accelerate into traffic just like nothing... it's getting plenty of gas; the secondaries are clearly working, and it runs great! In 10 minutes, it does it again. Wait a couple of minutes, start it up, and off we go again. I finally figured out I could keep it running if I went a lot slower like under 55 m.p.h. It seemed like it had enough fuel to maintain that speed, but no faster. We found a campground for the night.
Alternatively, of course, is that many of you are knowledgeable about all things Rochester (or all things GMC), and even if you haven't seen this manifestation, perhaps these symptoms are pointing to some particular part? Any help is appreciated!
Sure sounds like fuel. The thing that bothers me is the quick recovery. If it was vaporlock, the carburetor gets hotter when the engine stops. I would think it would not start in two minutes.
Are you sure you vapor canister-hoses-separator valve-hoses to the tank are all open. If the canister cannot let air into a tank to replace the missing gasoline you could develop a vacuum in the tanks. (We usually have a pressure buildup) One of the times it sounded like it could have been cool in the early evening. IF it does it again I would crack the gas cap slowly to see if you hear sucking or blowing. (Don't get a bath.)
Spark can do odd things. A weak spark (module or coil) can make an engine fail when the throttle is opened. Both coils and modules can fail with heat, but again they take a long time to cool enough to work again. Usually it doesn't cause simple power fade but has profound missing. But, it can just "cut out" when the throttle is open as well. It does this because when the throttle is open, more air is getting into the cylinders and raising the compression. Spark has a hard time jumping in dense conditions. So opening the throttle will make the spark fail.
I had a module that would stop working and key off, key on often revived it for a bit.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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Re: Quadrajet Conundrum [message #271284 is a reply to message #271272] |
Fri, 06 February 2015 07:12 |
Chris Tyler
Messages: 458 Registered: September 2013 Location: Odessa FL
Karma: 7
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Senior Member |
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I second the notion that the problem may lie with the power valve. If you have had one apart, it is the thing in the middle of the primary bowl that controls the metering rods in the primary jets
If it is sticking or the spring underneath is weak or broken the rods will not lift up providing enrichment.
You may have something clogging the jets or the main circuit
Float level may also be too low or hanging up
76 Glenbrook
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Re: [GMCnet] Quadrajet Conundrum [message #271285 is a reply to message #271272] |
Fri, 06 February 2015 07:22 |
Ken Henderson
Messages: 8726 Registered: March 2004 Location: Americus, GA
Karma: 9
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Senior Member |
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Vince,
Two weird possibilities come to mind:
1. During my trip West with my 16 yo grandson in early summer 2013, at
only 90*F and in the deepest of Death Valley, we had recurrent "vapor lock"
-- which would clear itself after just a few minutes beside the road. That
condition continued intermittently until Gunnison, CO on the way home.
There I replaced the ignition coil, which turned out during bench testing
back here to be temperature sensitive -- it would open only over a
temperature range of 200-250*F or so (IIRC). Since you probably should
carry a spare coil anyway, you might try replacing it.
2. Last week another GMCer and I were about to leave a campground in FL.
His engine, which was running great when parked a couple of weeks earlier,
refused to start. With no spray in the primary carb throats, we started
tracing fuel -- and found plenty all the way to the carb. The inlet filter
had already been removed. Finally, we saw that the manifold held pooled
gasoline, so he (much more QJ proficient than I) pulled the carb and
disassembled it. The only thing we could find wrong with it was that the
power valve piston was sticking. After using Comet, the only handy
abrasive, to polish the piston, he reassembled and reinstalled the carb.
The engine started right up and has run perfectly for the subsequent 500
miles. We don't know whether we fixed the problem unintentionally or by
the polishing.
By the way, IMHO it simplifies the fuel system, and subsequent
troubleshooting, while providing redundancy, if you eliminate the
mechanical fuel pump and the selector valve, replacing them with a
dedicated P4070 for each tank.
HTH,
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
On Fri, Feb 6, 2015 at 12:28 AM, Vince Kirkhuff
wrote:
> First, let me apologize for the length of this post...
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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Re: [GMCnet] Quadrajet Conundrum [message #271286 is a reply to message #271272] |
Fri, 06 February 2015 07:20 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Senior Member |
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Vince,
I have a similar setup on Double Trouble but my pump is a small Facet cube pump plumbed into the front (Aux) tank that puts our 4
psi whenever I switch to AUS.
I had the same problem when trying to climb Eisenhower pass a couple of years ago, I got lucky and inched my way to the top.
I discovered that when climbing a steep incline over a long period the fuel in the aux tank may not be high enough for the Facet
pump to supply enough flow / pressure to the main pump when vapor lock occurs.
My fix is to:
1) fill my tanks just before stopping for the night
2) fill my tanks the first thing in the morning
3) check / fill my tanks before starting a long climb
Regards,
Rob M.
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Vince Kirkhuff
Sent: Friday, February 06, 2015 4:28 PM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Quadrajet Conundrum
First, let me apologize for the length of this post... if you don't wish to read my diatribe, I understand; I won't be offended if
you choose to simply move on.
My name is Vince Kirkhuff; I have met some of you at some of the Western States Rallies. I've posted here only a handful of times,
because I can usually find the answer to any GMC situation by searching the Forum archives. I have not had any luck finding a
similar situation to what I am now experiencing.
I live in San Luis Obispo on the Central Coast of California. I drive a 1977 Eleganza II with the 455 and a stock Quadrajet. I've
owned it 6-1/2 years bought it from the original owner with 45,000 miles on it. It has about 56,000 on it now.
5 or so years ago I was experiencing classic vapor lock problems: Hot day, at altitude (3,500+ ft.), and starting off from an idle,
the engine would stumble and backfire through the carb or die altogether. In an attempt to correct his problem, I installed a
Carter P4070 electric fuel pump and inline filter just downstream from the tank selector valve. I used the selector valve as the
power source, so the pump only ran when the auxiliary tank was selected. The pump was on a by-pass loop, with a check valve in the
main line to keep all the gas moving toward the engine. The mechanical fuel pump was in its original configuration.
This worked pretty well until one hot day I was trying to climb Greeley Hill Rd. out of Greely Hill, California, which is a fairly
long, steep grade, and the fuel gauge was showing about ¼ tank. I was running the electric pump, due to vapor lock conditions, and
heading up that hill, all of the gas sloshed to the rear (main) tank. My auxiliary tank was now dry, so I had to switch back to the
main tank turning off the pump! The engine would not run at faster than an idle without the pump, but it wouldn't run at all on
the (dry) auxiliary tank. I had to back down this narrow, twisting, two-lane country road about a quarter of a mile to where I
could turn around. Luckily, I was able to nurse it the ½ mile or so back into town where there was a gas station.
So, my next modification was to hook up the electric pump to run all the time. I was happy to get rid of the bypass circuit with
the T's, the check valve, and about 10 hose clamps, I figure my potential for leaks was drastically reduced. I was now running both
the electric and mechanical pumps full time. It was with this set up that the Mysterious Lean Condition first manifested.
The first time I felt it do this, I was heading up Highway 5 me, the wife, the mother-in-law, and 3 dogs; on our way to a family
camp out. About 2 hours into our trip and this was nighttime it starts to feel like it's running out of gas; but I've still got
at least ½ a tank, according to the gauge. But I think I'm feeling it hesitate... then falter, then finally backfire through the
carb... this takes about 10 minutes, and 10 miles driving down the road. The more gas I give it, the worse it runs opening the
throttle is just leaning it out. The engine finally dies and we coast to a stop on the shoulder of the freeway.
So we sit there a minute, and I'm trying to think of what to do... diagnose my fuel problem? Am I going to repair it? On the side
of Hwy 5? In the dark? Call a tow truck? I'm thinking, if we weren't on the shoulder of the freeway, we could just go to bed and
worry about it in the morning. So then I'm thinking, if I can get it running, at least I can maybe get it off the freeway. So I
crank the engine, and it fires right up, and it runs fine, and we accelerate into traffic just like nothing... it's getting plenty
of gas; the secondaries are clearly working, and it runs great! In 10 minutes, it does it again. Wait a couple of minutes, start
it up, and off we go again. I finally figured out I could keep it running if I went a lot slower like under 55 m.p.h. It seemed
like it had enough fuel to maintain that speed, but no faster. We found a campground for the night.
In the morning, I called Kanomata's shop and talked to Nick, and he said yeah, it sounds like a lean fuel issue, and suggested a
fuel filter. So I bought one and replaced it when we got to our destination. We were there for 2 nights, and then headed home.
Out on the road it ran fine, so I thought I had fixed it. Then, a couple of hours into the drive, it started doing it again. We
had a slow drive home that day, just taking it easy in the slow lane. That was a year and a half ago.
Since then, we've only had it out on long enough drives to create the problem twice. (A lot of our trips are within an hour or so
of home, and it always runs fine for the first 90 minutes, at least.) I thought maybe something weird was happening between the 2
fuel pumps, so I have bypassed the mechanical pump. I also removed the fuel filter at the carb, and replaced the ignition module
for good measure. It still does it after those changes. It will do it with a nearly full tank of gas, a part tank, or nearly empty
main tank or auxiliary. The last time it did it, I got a big clue: when it started to feel like it was running out of gas, I pumped
the gas pedal like mad, and it ran better. So this makes me think the carb is getting fuel there's obviously fuel in the float
bowl, but for some reason it's running lean, and the accelerator pump enriches it enough so it runs okay. I was able to nurse it
along for about 10 miles down the freeway by pumping it to help it up little hills and such; but still, it eventually died. Again:
Wait 1 or 2 minutes, and it starts and runs fine.
Before I took it out on that last road trip, I searched the Forum archives for similar problems, but didn't find one exactly like
mine... in that my problem fixes itself with a few minutes' rest. Thinking it may be electrical, I contacted Dick Patterson, who
thought it sounded like a fuel problem and promptly talked me out of buying a distributor from him. It was his suggestion to remove
the fuel filter at the carb, and check all the primary coil connections as well as the ignition module connections. I also
installed a temporary pilot light to tell me if the fuel pump has power (it does). The tanks were dropped 4 years ago (very clean
at that time) and new rubber lines were installed.
I read one story on the interweb of some guy with a Camaro or a Chevelle with a similar sounding problem, and he found it to be a
problem with the power piston in the Q-jet something about a little plastic clip that holds the top of it, and it had broken and was
getting in there sideways but I don't know enough about carburetors to know if that experience is applicable to my situation. I'm
hoping that one of you all has maybe run into this same situation and knows just the thing to fix it.
Alternatively, of course, is that many of you are knowledgeable about all things Rochester (or all things GMC), and even if you
haven't seen this manifestation, perhaps these symptoms are pointing to some particular part? Any help is appreciated!
--
Vince Kirkhuff
1977 Eleganza II
San Luis Obispo, CA
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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Re: Quadrajet Conundrum [message #271287 is a reply to message #271272] |
Fri, 06 February 2015 08:06 |
kerry pinkerton
Messages: 2565 Registered: July 2012 Location: Harvest, Al
Karma: 15
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Senior Member |
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My first thought was that this sounded very much like the problem that Ken Henderson had in the fall of 2013. There were several threads about it and if you search for "Vapor Lock" and also user "Ken Henderson" you will find them. EVERYONE seemed to think it was fuel related and, as Ken described, it turned out to be the coil that would fail at a certain temperature range, and 'unfail' when it got hotter.
I'm also a proponent of keeping the tanks full but will note that if we fill up just before stopping, we get a pretty strong gas smell. I like to drive at least an hour on full tanks. That is just us.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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Re: [GMCnet] Quadrajet Conundrum [message #271296 is a reply to message #271286] |
Fri, 06 February 2015 10:51 |
Mr ERFisher
Messages: 7117 Registered: August 2005
Karma: 2
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Senior Member |
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Need to connect the drains
On Friday, February 6, 2015, Robert Mueller wrote:
> Vince,
>
> I have a similar setup on Double Trouble but my pump is a small Facet cube
> pump plumbed into the front (Aux) tank that puts our 4
> psi whenever I switch to AUS.
>
> I had the same problem when trying to climb Eisenhower pass a couple of
> years ago, I got lucky and inched my way to the top.
>
> I discovered that when climbing a steep incline over a long period the
> fuel in the aux tank may not be high enough for the Facet
> pump to supply enough flow / pressure to the main pump when vapor lock
> occurs.
>
> My fix is to:
>
> 1) fill my tanks just before stopping for the night
> 2) fill my tanks the first thing in the morning
> 3) check / fill my tanks before starting a long climb
>
> Regards,
> Rob M.
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces@temp.gmcnet.org ] On
> Behalf Of Vince Kirkhuff
> Sent: Friday, February 06, 2015 4:28 PM
> To: gmclist@temp.gmcnet.org
> Subject: [GMCnet] Quadrajet Conundrum
>
> First, let me apologize for the length of this post... if you don't wish
> to read my diatribe, I understand; I won't be offended if
> you choose to simply move on.
>
> My name is Vince Kirkhuff; I have met some of you at some of the Western
> States Rallies. I've posted here only a handful of times,
> because I can usually find the answer to any GMC situation by searching
> the Forum archives. I have not had any luck finding a
> similar situation to what I am now experiencing.
>
> I live in San Luis Obispo on the Central Coast of California. I drive a
> 1977 Eleganza II with the 455 and a stock Quadrajet. I've
> owned it 6-1/2 years bought it from the original owner with 45,000 miles
> on it. It has about 56,000 on it now.
>
> 5 or so years ago I was experiencing classic vapor lock problems: Hot
> day, at altitude (3,500+ ft.), and starting off from an idle,
> the engine would stumble and backfire through the carb or die altogether.
> In an attempt to correct his problem, I installed a
> Carter P4070 electric fuel pump and inline filter just downstream from the
> tank selector valve. I used the selector valve as the
> power source, so the pump only ran when the auxiliary tank was selected.
> The pump was on a by-pass loop, with a check valve in the
> main line to keep all the gas moving toward the engine. The mechanical
> fuel pump was in its original configuration.
>
> This worked pretty well until one hot day I was trying to climb Greeley
> Hill Rd. out of Greely Hill, California, which is a fairly
> long, steep grade, and the fuel gauge was showing about ¼ tank. I was
> running the electric pump, due to vapor lock conditions, and
> heading up that hill, all of the gas sloshed to the rear (main) tank. My
> auxiliary tank was now dry, so I had to switch back to the
> main tank turning off the pump! The engine would not run at faster than
> an idle without the pump, but it wouldn't run at all on
> the (dry) auxiliary tank. I had to back down this narrow, twisting,
> two-lane country road about a quarter of a mile to where I
> could turn around. Luckily, I was able to nurse it the ½ mile or so back
> into town where there was a gas station.
>
> So, my next modification was to hook up the electric pump to run all the
> time. I was happy to get rid of the bypass circuit with
> the T's, the check valve, and about 10 hose clamps, I figure my potential
> for leaks was drastically reduced. I was now running both
> the electric and mechanical pumps full time. It was with this set up that
> the Mysterious Lean Condition first manifested.
>
> The first time I felt it do this, I was heading up Highway 5 me, the
> wife, the mother-in-law, and 3 dogs; on our way to a family
> camp out. About 2 hours into our trip and this was nighttime it starts
> to feel like it's running out of gas; but I've still got
> at least ½ a tank, according to the gauge. But I think I'm feeling it
> hesitate... then falter, then finally backfire through the
> carb... this takes about 10 minutes, and 10 miles driving down the road.
> The more gas I give it, the worse it runs opening the
> throttle is just leaning it out. The engine finally dies and we coast to
> a stop on the shoulder of the freeway.
>
> So we sit there a minute, and I'm trying to think of what to do...
> diagnose my fuel problem? Am I going to repair it? On the side
> of Hwy 5? In the dark? Call a tow truck? I'm thinking, if we weren't on
> the shoulder of the freeway, we could just go to bed and
> worry about it in the morning. So then I'm thinking, if I can get it
> running, at least I can maybe get it off the freeway. So I
> crank the engine, and it fires right up, and it runs fine, and we
> accelerate into traffic just like nothing... it's getting plenty
> of gas; the secondaries are clearly working, and it runs great! In 10
> minutes, it does it again. Wait a couple of minutes, start
> it up, and off we go again. I finally figured out I could keep it running
> if I went a lot slower like under 55 m.p.h. It seemed
> like it had enough fuel to maintain that speed, but no faster. We found a
> campground for the night.
>
> In the morning, I called Kanomata's shop and talked to Nick, and he said
> yeah, it sounds like a lean fuel issue, and suggested a
> fuel filter. So I bought one and replaced it when we got to our
> destination. We were there for 2 nights, and then headed home.
> Out on the road it ran fine, so I thought I had fixed it. Then, a couple
> of hours into the drive, it started doing it again. We
> had a slow drive home that day, just taking it easy in the slow lane.
> That was a year and a half ago.
>
> Since then, we've only had it out on long enough drives to create the
> problem twice. (A lot of our trips are within an hour or so
> of home, and it always runs fine for the first 90 minutes, at least.) I
> thought maybe something weird was happening between the 2
> fuel pumps, so I have bypassed the mechanical pump. I also removed the
> fuel filter at the carb, and replaced the ignition module
> for good measure. It still does it after those changes. It will do it
> with a nearly full tank of gas, a part tank, or nearly empty
> main tank or auxiliary. The last time it did it, I got a big clue: when
> it started to feel like it was running out of gas, I pumped
> the gas pedal like mad, and it ran better. So this makes me think the
> carb is getting fuel there's obviously fuel in the float
> bowl, but for some reason it's running lean, and the accelerator pump
> enriches it enough so it runs okay. I was able to nurse it
> along for about 10 miles down the freeway by pumping it to help it up
> little hills and such; but still, it eventually died. Again:
> Wait 1 or 2 minutes, and it starts and runs fine.
>
> Before I took it out on that last road trip, I searched the Forum archives
> for similar problems, but didn't find one exactly like
> mine... in that my problem fixes itself with a few minutes' rest.
> Thinking it may be electrical, I contacted Dick Patterson, who
> thought it sounded like a fuel problem and promptly talked me out of
> buying a distributor from him. It was his suggestion to remove
> the fuel filter at the carb, and check all the primary coil connections as
> well as the ignition module connections. I also
> installed a temporary pilot light to tell me if the fuel pump has power
> (it does). The tanks were dropped 4 years ago (very clean
> at that time) and new rubber lines were installed.
>
> I read one story on the interweb of some guy with a Camaro or a Chevelle
> with a similar sounding problem, and he found it to be a
> problem with the power piston in the Q-jet something about a little
> plastic clip that holds the top of it, and it had broken and was
> getting in there sideways but I don't know enough about carburetors to
> know if that experience is applicable to my situation. I'm
> hoping that one of you all has maybe run into this same situation and
> knows just the thing to fix it.
>
> Alternatively, of course, is that many of you are knowledgeable about all
> things Rochester (or all things GMC), and even if you
> haven't seen this manifestation, perhaps these symptoms are pointing to
> some particular part? Any help is appreciated!
>
> --
> Vince Kirkhuff
> 1977 Eleganza II
> San Luis Obispo, CA
>
>
> _______________________________________________
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>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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Re: Quadrajet Conundrum [message #271297 is a reply to message #271290] |
Fri, 06 February 2015 11:17 |
Otterwan
Messages: 946 Registered: July 2013 Location: Lynnwood (north of Seattl...
Karma: 0
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I had a Mercury outboard that would run great up to about half throttle, then sputter and die. I tried everything with no luck. Turned out to be a collapsed fuel line. If your fuel lines are stock, I would definitely check them.
Also, as we used to say, "90% of carburetor problems are in the ignition" ;o)
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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Re: Quadrajet Conundrum [message #271310 is a reply to message #271272] |
Fri, 06 February 2015 14:52 |
mild bill
Messages: 98 Registered: November 2014 Location: Edmonton, Alberta, Canada
Karma: 0
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While I agree it could be ignition related I would think that after it stalls it operates normally after a couple minutes and a stalled engine would normally heat sink the elevated engine temps to the ignition components resulting from heat transfer from a non circulating cooling cooling system. Sounds more like when you forget to open the vent on a tank for your outboard engine. One way to test is drill a 1/8" hole in the gas cap and see if it happens again. All this talk of pressurized tanks blowing out fuel and seeing what my lines were like with collapsed and missing body mounts could be causing these problems. While tanks used to be vented at the gas cap and venting the cap could be a viable troubleshooting method if it works I would still delve to fix the problem properly.
Could also be an ignition switch heating up, check voltage drop to coil cold and after it stalls, ignition switch would cool down quicker than the module or coil, but for the price I would throw those parts at it also. But one or two fixes at a time so you can determine the culprit .
So when I say one or two fixes at a time, I would drill the gas cap first, cheapest troubleshooting.
If that doesn't fix it check coil voltage at time of stall, if ok drop a new distributor in it to take care of all variables in the ignition system.
[Updated on: Fri, 06 February 2015 15:06] Report message to a moderator
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Re: [GMCnet] Quadrajet Conundrum [message #271315 is a reply to message #271313] |
Fri, 06 February 2015 16:51 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Got it, thanks!
Regards,
Rob M.
-----Original Message-----
From: gene Fisher
Like bounds does so there is only one tank
On Friday, February 6, 2015, Robert Mueller wrote:
> Gene,
>
> Drains?
>
> Regards,
> Rob M.
>
> -----Original Message-----
> From: gene Fisher
>
> Need to connect the drains
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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