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| Re: Quadrajet Conundrum [message #271327 is a reply to message #271277] |
Fri, 06 February 2015 19:57   |
Vince Kirkhuff
Messages: 12
Registered: May 2009
Karma: 0
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Junior Member |
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Thanks, Terry... I will be checking out the main jets, but I'll also be checking the tank venting and charcoal canister... that seems like a possibility. By all means, stop in when you're in Pismo!
Vince Kirkhuff
1977 Eleganza II
San Luis Obispo, CA
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| Re: Quadrajet Conundrum [message #271330 is a reply to message #271327] |
Fri, 06 February 2015 22:08 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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You're welcome Vince, hope you find the problem easy to fix. If the GMC makes it from this coast to that one you might be able to see it from 101 if you drive by, we'll be on Wilmar ave (actually may be parked on the next street down)a few houses from the beach. I'll definitely try to catch up with a few people while I'm out there. Right now I think I need to go out and fire up the furnace for a few minutes!
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: Quadrajet Conundrum [message #271337 is a reply to message #271272] |
Sat, 07 February 2015 02:21 |
Gadabout
Messages: 124
Registered: March 2013
Location: Edmonton
Karma: 2
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Senior Member |
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Hi Vince,
Best Guess = fuel strainer at the pickup and/or carb.
I have rebuilt several Rochester carbs with good success. I even had to do the one on the Pawn Stars Gadabout in a Motel parking lot just so we could finish the trip home.
I agree with your theory that the problem is fuel related and I suspect that you have two issues, the Rochester and the fuel pickup.
My theory is that the fuel pickup in the tank has started to erode, this erosion has shortened the pickup. Particles have made there way into the carb resulting in the symptoms you are experiencing. Or the strainer at the pickup is collapsed or plugged.
As your engine shuts off on a steep incline, I suspect it is related to the fuel pickup in the fuel tank or inaccurate fuel gauge and your just out of gas.
Low fuel delivery at applied throttle resulting in no power could be a plugged strainer, fuel filter or carb problem. As you have already done the filter, that leaves the strainer and carb.
Carb issues can be faulty float, sticky needle/seat , plugged vents, power piston, plugged jets or a combination of several items. There is also a setting for what is referred to as the Applied Part Throttle (APT), it is set at the factory and should not be changed.
Carbs need to be serviced , gaskets and seals dry out when the vehicle is not used for an extended period and the carb gets gummed up with particles suspended in the fuel.
You can try to clear the strainer without removing the tank by disconnecting he suction side at the fuel pump and blowing low pressure into the the fuel pickup line.
Good luck with it and let us know what the problem was when you get it resolved.
Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
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| Re: Quadrajet Conundrum [message #271338 is a reply to message #271290] |
Sat, 07 February 2015 04:01 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The 455 has a humongous exhaust crossover underneath the carb. It is way to large for our application. Upon installation a new manifold immediately burns the paint off the intake and chars any oil that hits the bottom of the intake manifold. If you run any hose like a vacuum hose across the top of the manifold if will melt it. It will also boil the carb dry on shut down. Our intake manifolds have a problem with cracking the intake from the excess high heat. Many of us have blocked the crossover to reduce the excess heat applied to the carb. I am very familiar with carb icing in aircraft and have had it in other automotive applications. Carb icing is not a problem in a GMC.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Quadrajet Conundrum [message #271384 is a reply to message #271272] |
Sat, 07 February 2015 23:21 |
mild bill
Messages: 98
Registered: November 2014
Location: Edmonton, Alberta, Canada
Karma: 0
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First of all he mentioned once where he was going up a steep incline and he stalled on the aux tank and changed his pusher pump configuration. He did not indicate that this only happens going up steep hills. Yes it could be a plugged sock or rotted off pickup or maby someone threw a plastic bag in his fuel filler and it occasionally plugs the pickup, (seen it) however it runs for 90 minutes perfectly fine, and after a short time after stalling what I read it runs perfectly fine including strong secondary operation till the problem occurs again.
Rust particles in the bowl can sometimes float around and plug jets however I don't think the engine would normally run fine for 90 minutes as well as for them to get there you woul have had a history of engine flooding while they were going through the needle and seat.
Float problems, only one I saw was a saturated float weighing more than it should causing a over rich or flooding engine.
[Updated on: Sun, 08 February 2015 12:25] Report message to a moderator |
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| Re: Quadrajet Conundrum [message #271397 is a reply to message #271272] |
Sun, 08 February 2015 09:34 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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After re reading your post I'm going with ignition. If fuel delivery, it would first show up at sustained WOT where demand can't keep up over time and get worse from there. Could be heat sensitve coil, module thermal grease dried up or cracked lead wires from the pickup coil. Fuel is usually more a "soft edged" failure and yours sounds more sudden and "hard edged" If it was stuck power valve, when flooring it the secondaries would flow enough to cover that problem up.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Quadrajet Conundrum [message #271415 is a reply to message #271272] |
Sun, 08 February 2015 13:41 |
Vince Kirkhuff
Messages: 12
Registered: May 2009
Karma: 0
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Junior Member |
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Gentlemen (and the rest of you, too):
Thanks so much for all of your replies. You've given me many weekends of projects in checking out the many theories. I'm leaning toward the partially-or-mostly clogged fuel tank vent theory, and this is why:
1) The fuel tanks, pickups, and screens were clean and in good shape when I dropped the tanks 4 years ago.
2) The ignition module was replaced, with new thermal grease, since this problem has started. (The thermal grease looked fine on the old module, too.)
3) The problem started when I removed the fuel line bypass, thus preventing the mechanical pump from having direct access to the tank (it had to draw through the electric pump). My theory is that the mechanical pump creates more suction than does the electric pump, so the mechanical pump could draw through the clogged vent, where the electric pump only draws until there is too much vacuum in the tank, then stops (or at least slows a lot).
4) A brief stop of only a few minutes allows the vacuum in the tank to draw in air (through the clogged vent or any other leaks in the system) and equalize with atmospheric pressure enough to start the fuel flow again, but in 10 or 15 minutes, it has built up vacuum again, and the problem recurs.
5) It will be simple to check: just drive it until the problem occurs, then loosen the gas cap; keep going and see if it does it again.
6) I've got a test gauge that I could hook up temporarily (duct-taped to the side view mirror, maybe)to keep an eye on the fuel pressure.
7) The only thing this doesn't explain is: how is it that there is fuel in the float bowl for the accelerator pump to pick up, if the fuel pump is not delivering fuel?
 I'll bring a spare coil with me on the test drive, to install when the problem recurs.
Vince Kirkhuff
1977 Eleganza II
San Luis Obispo, CA
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| Re: Quadrajet Conundrum [message #271438 is a reply to message #271272] |
Sun, 08 February 2015 19:40 |
mild bill
Messages: 98
Registered: November 2014
Location: Edmonton, Alberta, Canada
Karma: 0
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Sorry for not being a gentleman last night, crappy day at work and sick wife ticked that I'm working the weekend again on my 4 and 4 shift. That with half the appliances in my house have died in the last week and to much alcohol.. Well.
IM also not the kind of person that would accept gm,s direction that I shouldn't adjust something when I was taught by someone who IMO was one of the best fuel and electrical men I have ever met and the tricks he taught me have made many hundreds of happy customers over the last 38 years. But yeah I agree. I went off on a bit of a tangent so sorry to you all and especially Carl.
Save the initial drive, drill the gas cap or leave it loose but even lossened off vacuum in the fuel system could seal the cap again while you go down the road. If it doesn't die be happy.
Busy day but the funny part of my day, not for Alaskan Airlines, was seeing their Canadair RJ 700 with a water truck parked under it and the RJ's nose wheel 12" off the ground. I guess the operator said his boot got stuck between the gas pedal and brake pedal as he was backing up, not my problem, we don't handle them except for AC Mtc. Moved the aircraft over about 14' off centreline (quite a feat considering the mains were chocked) and extensive damage including nose gear. Bridge was backed off enough so he didn't damage that side of the aircraft. My day yesterday pales in comparison to his im sure. Millions!
[Updated on: Sun, 08 February 2015 20:14] Report message to a moderator |
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| Re: Quadrajet Conundrum [message #271447 is a reply to message #271272] |
Sun, 08 February 2015 21:50 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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If you search the archives Ken Henderson went through this saga for quite some time and it was a broken thermally sensitive HEI coil. He proved this on the bench with a meter and heat gun. The thing to learn here is that heat made it fail(open)by thermal expansion but more heat made it reconnect and work again. There was a temp window where it was bad.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Quadrajet Conundrum [message #273379 is a reply to message #273294] |
Mon, 09 March 2015 12:22 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
Karma: 0
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Senior Member |
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Ironicly i am to dealing with this same issue and for me it sees to be air being sucked in or vapor locking super quickly. My story i had rusty tanks and installed a inline glass see through filter before the fuel pump under the front by the front cross member so i could see the crap and or try and filter out in hopes of not dropping the tanks. It would run decent until the Qjet filter would get clogged and then it would start surging backfiring/starving for fuel. So bit the bullet and had the tanks and fuel lines redone. When I picked her up she ran great for a bit and the gas coming through the see through filter was now super clean ..YAY...NOT ! What i am now seeing is tuns of air bubbles accuimulating and sloshing in the filter is this vapor lock ? Or bad venting/canister issue it happens about 10 mins into firing her up. I took it back to the shop and they claimed they have rechecked connections and found nothing a miss. Not very confident in their work but what i do know is i can see what exactly is happing its definitly starving becouse of the air or vapor lock deal but still scratching my head as waht to do. I have removed most hoses at fuel seperator,fill vent canister etc. and seems they are clear and not pinched as far as i can tell. I did add a electric fuel pump as others have done at the Aux. tank line before the selector valve and wired off of there over the weekend as it seems to of helped. Still acts up even when i hit the pump to push/eleviate air in the line. Now im gonna replace the fuel pump thinking that maybe the diaphram could be causing some sort of issue. Quite a mystery for me but i guess this is what we live for HAHA ! Any help would be great and please let us know what you figure out. Try the see throug filter and see what you see ? When this starts to happen at least you can see if its vapor locking before the pump/carb as mine is which seems to be the case most of the time for us GMCR's . I do have a massive exaust manifld leak on passenger side and could be blowing heat right onto the inlet fuel line where i have the inline see through filter. Ughh
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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| Re: [GMCnet] Quadrajet Conundrum [message #273387 is a reply to message #273379] |
Mon, 09 March 2015 13:10 |
Daniel DeLuca
Messages: 120
Registered: June 2014
Karma: 0
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Senior Member |
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Tony,
This is probably not the issue with your setup, but I was pulling my hair out dealing with similar issues after flushing the tanks, replacing all fuel lines and rebuilding the carb. Finally had a more knowledgeable friend over who look looked at it said “It’s Running out of gas” and replaced the fuel filter. Even though I had just replaced it, turns out that was all it was, ran fine ever since. It really doesn’t take much to clog one and you stir up all sorts of stuff when your resurrect one of these things.
Dan
78 Eleganza
Central Jersey
> On Mar 9, 2015, at 1:22 PM, Tony Cook wrote:
>
> Ironicly i am to dealing with this same issue and for me it sees to be air being sucked in or vapor locking super quickly. My story i had rusty tanks
> and installed a inline glass see through filter before the fuel pump under the front by the front cross member so i could see the crap and or try and
> filter out in hopes of not dropping the tanks. It would run decent until the Qjet filter would get clogged and then it would start surging
> backfiring/starving for fuel. So bit the bullet and had the tanks and fuel lines redone. When I picked her up she ran great for a bit and the gas
> coming through the see through filter was now super clean ..YAY...NOT ! What i am now seeing is tuns of air bubbles accuimulating and sloshing in the
> filter is this vapor lock ? Or bad venting/canister issue it happens about 10 mins into firing her up. I took it back to the shop and they claimed
> they have rechecked connections and found nothing a miss. Not very confident in their work but what i do know is i can see what exactly is happing its
> definitly starving becouse of the air or vapor lock deal but still scratching my head as waht to do. I have removed most hoses at fuel seperator,fill
> vent canister etc. and seems they are clear and not pinched as far as i can tell. I did add a electric fuel pump as others have done at the Aux. tank
> line before the selector valve and wired off of there over the weekend as it seems to of helped. Still acts up even when i hit the pump to
> push/eleviate air in the line. Now im gonna replace the fuel pump thinking that maybe the diaphram could be causing some sort of issue. Quite a
> mystery for me but i guess this is what we live for HAHA ! Any help would be great and please let us know what you figure out. Try the see throug
> filter and see what you see ? When this starts to happen at least you can see if its vapor locking before the pump/carb as mine is which seems to be
> the case most of the time for us GMCR's . I do have a massive exaust manifld leak on passenger side and could be blowing heat right onto the inlet
> fuel line where i have the inline see through filter. Ughh
> --
> Tony Cook
> 77' Kingsley ' SuperSession 77 '
> Torrance Beach,CA
> _______________________________________________
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> Unsubscribe or Change List Options:
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| Re: [GMCnet] Quadrajet Conundrum [message #273389 is a reply to message #273387] |
Mon, 09 March 2015 13:36 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
Karma: 0
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Senior Member |
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Totally hear ya on the Qjet filter i have become a pro on replacing them in like 5 min. Flat ! Lol that was the case before having tanks and lines redone but now it is most definitely starving because of the air / vapor happening before the fuel pump as i can see it happening with the clear filter i added before the fuel pump . They start off very small when viewing through the see through filter and then ends up like a wooshing sloshing session happening causing the lean issue. All I'm saying is i now can see most definitely what is happening just now trying to figure out how to remedy it ? Switching on the pusher pump does help i can see when i engage the pusher pump it preaserize's the line but doesn't seem to totally cure it.
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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| Re: [GMCnet] Quadrajet Conundrum [message #273399 is a reply to message #273387] |
Mon, 09 March 2015 17:54 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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Just make sure that they are installed correctly, as if it is in backwards then the motor will be starved for fuel. Had a friend a couple of years ago that had changed is carb fuel filter. Got about 30 miles down the road and it started to run poorly. Checked a number of possible trouble points and then another of our traveling band took one more look at the carb fuel and found it installed backwards.
J.R. Wright
30' Buskirk Stretch
Michigan
On Location in Tucson
> On Mar 9, 2015, at 11:10 AM, Daniel DeLuca wrote:
>
> Tony,
>
> This is probably not the issue with your setup, but I was pulling my hair out dealing with similar issues after flushing the tanks, replacing all fuel lines and rebuilding the carb. Finally had a more knowledgeable friend over who look looked at it said “It’s Running out of gas” and replaced the fuel filter. Even though I had just replaced it, turns out that was all it was, ran fine ever since. It really doesn’t take much to clog one and you stir up all sorts of stuff when your resurrect one of these things.
>
> Dan
> 78 Eleganza
> Central Jersey
>> On Mar 9, 2015, at 1:22 PM, Tony Cook wrote:
>>
>> Ironicly i am to dealing with this same issue and for me it sees to be air being sucked in or vapor locking super quickly. My story i had rusty tanks
>> and installed a inline glass see through filter before the fuel pump under the front by the front cross member so i could see the crap and or try and
>> filter out in hopes of not dropping the tanks. It would run decent until the Qjet filter would get clogged and then it would start surging
>> backfiring/starving for fuel. So bit the bullet and had the tanks and fuel lines redone. When I picked her up she ran great for a bit and the gas
>> coming through the see through filter was now super clean ..YAY...NOT ! What i am now seeing is tuns of air bubbles accuimulating and sloshing in the
>> filter is this vapor lock ? Or bad venting/canister issue it happens about 10 mins into firing her up. I took it back to the shop and they claimed
>> they have rechecked connections and found nothing a miss. Not very confident in their work but what i do know is i can see what exactly is happing its
>> definitly starving becouse of the air or vapor lock deal but still scratching my head as waht to do. I have removed most hoses at fuel seperator,fill
>> vent canister etc. and seems they are clear and not pinched as far as i can tell. I did add a electric fuel pump as others have done at the Aux. tank
>> line before the selector valve and wired off of there over the weekend as it seems to of helped. Still acts up even when i hit the pump to
>> push/eleviate air in the line. Now im gonna replace the fuel pump thinking that maybe the diaphram could be causing some sort of issue. Quite a
>> mystery for me but i guess this is what we live for HAHA ! Any help would be great and please let us know what you figure out. Try the see throug
>> filter and see what you see ? When this starts to happen at least you can see if its vapor locking before the pump/carb as mine is which seems to be
>> the case most of the time for us GMCR's . I do have a massive exaust manifld leak on passenger side and could be blowing heat right onto the inlet
>> fuel line where i have the inline see through filter. Ughh
>> --
>> Tony Cook
>> 77' Kingsley ' SuperSession 77 '
>> Torrance Beach,CA
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Unsubscribe or Change List Options:
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| Re: [GMCnet] Quadrajet Conundrum [message #273400 is a reply to message #273389] |
Mon, 09 March 2015 18:10 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Tony Cook wrote on Mon, 09 March 2015 13:36Totally hear ya on the Qjet filter i have become a pro on replacing them in like 5 min. Flat ! Lol that was the case before having tanks and lines redone but now it is most definitely starving because of the air / vapor happening before the fuel pump as i can see it happening with the clear filter i added before the fuel pump . They start off very small when viewing through the see through filter and then ends up like a wooshing sloshing session happening causing the lean issue. All I'm saying is i now can see most definitely what is happening just now trying to figure out how to remedy it ? Switching on the pusher pump does help i can see when i engage the pusher pump it preaserize's the line but doesn't seem to totally cure it.
Tony
Have you considered there may be a split in a rubber hose allowing air to be sucked in?
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Quadrajet Conundrum [message #273409 is a reply to message #273400] |
Mon, 09 March 2015 19:35 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
Karma: 0
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Senior Member |
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Carb inlet filter in properly but yes have made that mistake once...once ! Lol. Hoses have all been replaced as far as i can see they look good but yea still trying to get to the 'bottom' of this one. Has anyone had good luck with the 3 port fuel pump deal routing the 1/4" port back to the filler neck ? Contemplating doing this as i need to replace my old tired fuel pump anyways. I seen on here some have done this and its to the filler neck and not the filler vent correct ? Thanks
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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| Re: Quadrajet Conundrum [message #273420 is a reply to message #271272] |
Mon, 09 March 2015 20:21 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
Karma: 0
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Senior Member |
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Yes i don't think its fuel pump either but i do need to change probably original. And yes thinking selector valve needs replacing as well just weird it does this in either or tank in use.
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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