Home » Public Forums » GMCnet » A couple 'issues' I'd like some advice on. (A 'cough' and low vacuum)
| A couple 'issues' I'd like some advice on. [message #270901] |
Sat, 31 January 2015 19:55  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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I've got a couple things going on and I'd appreciate some wisdom from the brain trust. I have some ideas but I'm scratching my head.
Some history and then some facts.
77 403 26' pull a Saturn toad and have a Powerdrive and a 3.21 which ends up as a 3.66 final drive ratio. 65mph is about 3000 RPM.
Motor was rebuilt about 5000 miles back, As of yesterday, compression is 150-165. All but 1 cylinder (#4) is between 165-160. Patterson carb and distributor with his plugs and wires replace when the engine done. All electric fuel pumps. Two pumps outside the tanks, filters before each pump, another filter before the engine, and the carb filter. Switching to the other tank changes which fuel pump is on.
A couple months back, I replaced the timing gears with a 4 degree advanced set. At the same time, I changed my vacuum gauge from an elcheapo gauge that had a range from 10 to 2 o'clock, to a S&W guage that sweeps from 7 to 5 o'clock. Readings on the vacuum match a large old mechanics vacuum gauge that was my Dad's back in the late 30's and has always been very accurate.
When I first started the engine after replacing the timing chains, it had been sitting for a couple months while I replaced the tranny. The motor idled like crap. Rough, popping through the carb. It would smooth out as it warmed up but still ran a bit rough. Yes, the modulator vacuum hose is on and functioning correctly. I talked to Dick Patterson and went through the timing, dead on 12 degrees with the vacuum adv off and plugged. Verified the mechanical advance is working, also verified the vacuum advance is working. Dinked with it a bit over a couple days and things got better as far as the idle was concerned but never really changed anything. I moved the timing a degree or two but was at 12 when I started and ended up at 11. Backed out the idle screws about 1/4 turn. About this time I drove the coach and noticed the vacuum seemed a bit low. 55 mph steady and level was about 10 inches of mercury. Hot idle was about 16.
Talked to Dick again wondering if the advancing the cam timing 4 degrees would effect the vacuum. He said no and thought it was a vacuum leak. I dinked with the timing and got it up to about 12 at 55 mph steady and level road. I've checked everything I can for vacuum leaks. New PVC valve, removed the booster vac line and plugged it. No change on vacuum gauge. Carb bolts are tight, modulator is hooked up. Everything is capped. The fact that I've got 18 at hot idle makes me think it's not a vacuum leak because I'd THINK that a big vacuum leak would show up more at idle than at higher RPM?????
Problem #1 is the vacuum level. The coach runs fine. Pulls stronger than before. BUT at 65mph on a level road just pulling against the wind and maintaining speed, my vacuum is 7-8. I watched it all the way to Tampa and back. Runs fine, just lower vacuum than I thought it was before. At 55, level and steady, I read 12-13. At 65, level and steady but obviously a heavier wind load (don't forget I'm towing too), I'm at 7-8. Btw the toad brakes and coach Ebrake are clear and rolling free.
So the question is, what kind of vacuum do you get a 65 level and steady? Dick said since the coach was running fine, I should put a piece of electrical tape on the vacuum gauge and just drive it. He might be right but I THINK it was about 5 inches higher before I advanced the cam timing. I don't THINK advancing the cam timing should effect the vacuum much if any. If I set the timing for max vacuum, I can get hot idle vacuum up near 18-19 but the timing mark is almost out of sight...probably 25-30 degrees of advance and that's with vacuum off and 700 RPM.
Problem #2 is a "cough". Not a backfire, just a 'chu'. Happened a couple times on the way to Tampa and 6-10 more on the way home. Its not much, just enough that the wife sometimes asks, "What was that?"
Remember the rough running that seemed to go away right after I got it running again.
One more data point. On the way home, we stopped for lunch and I started the Onan. Ran like crap. Wouldn't come to speed and stabilize enough for the automatic transfer switch to turn on the 120. Turned it off and came on home. Now it starts and runs BETTER but still rough, it will at least trip the transfer switch on. My buddy Beau thought it was crap in the carb.
I'm wondering if it is water in the tanks? This trip had 1600 miles of buying today's ethanol laced crap. Other than one tank starting out, and a stop at a big Shell in Florida (Ken and Stick also filled up there and have reported no problems) all the gas was purchased at big truck stops, Flying J, Petro, etc. I'd have thought that any water would have been flushed out,
I've thought about plugged fuel filters. Wide open throttle is no problem and I'd think it would be if there was a partially blocked filter.
It's not repeatable. 10 times in 1600 miles. It SEEMS to happen when I'm transitioning from a level pull or downhill to more throttle at about 2600 rpm. Just a little 'chuu'. Not a bang, not a pop, not loud, literally sounds like a muffled cough.
So today, I checked the timing again with TWO timing lights. 12 degrees.
Ken Henderson loaned me a wide band O2 sensor and I welded a bung up close to the engine and hooked it up.
At cold idle (700 rpm) with the choke about closed it read 10.4
warm idle with half choke was 12.1
hot idle (hot enough that the oil cooler fan was on so the oil temp was > 180), the ratio was 12.4 climbing to 13.2 as it ran a bit more.
IN PARK (it was getting late and I did not drive it today)
700 RPM 13.2
1300 RPM 12.0
2000 RPM 14.6
2500 RPM 15.7
3000 RPM 15.9
That's all the data I have.
In summary, I have two issues. They might or might not be related:
1- Low vacuum? (or perhaps it's just fine???)
2- The cough? Water?? Add a couple bottles of denatured alcohol??
Your thoughts, advice, etc are solicited. Please try not to hijack this thread. If you want to talk about something else, please start another thread.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] A couple 'issues' I'd like some advice on. [message #270904 is a reply to message #270901] |
Sat, 31 January 2015 20:46  |
Nelson
Messages: 120
Registered: August 2014
Karma: 0
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Senior Member |
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Kerry,
Why not pull one of the fuel tank drain plugs and see if there is water in the fuel. It should be the first thing out of the bottom of the tank. Pour it in a clear jar and let it settle and the water will be obvious .
BTW Not to hijack your thread, I did a check for ethanol in the gas at my local 7-11 and didn't find any, using the cake coloring test. If anyone wants to comment on this please start a new thread. With the price of gas below $2 it makes sense that ethanol would not be cost effective. Also since ethanol and water will mix and burn off maybe this is what is causing your "cough" and rough running Onan. In other words the absence of ethanol is what has changed.
HTH,
Nelson Wright
Orlando FL
78 Royale rear bath
On Jan 31, 2015, at 8:56 PM, Kerry Pinkerton wrote:
> I've got a couple things going on and I'd appreciate some wisdom from the brain trust. I have some ideas but I'm scratching my head.
>
> Some history and then some facts.
>
> 77 403 26' pull a Saturn toad and have a Powerdrive and a 3.21 which ends up as a 3.66 final drive ratio. 65mph is about 3000 RPM.
>
> Motor was rebuilt about 5000 miles back, As of yesterday, compression is 150-165. All but 1 cylinder (#4) is between 165-160. Patterson carb and
> distributor with his plugs and wires replace when the engine done. All electric fuel pumps. Two pumps outside the tanks, filters before each pump,
> another filter before the engine, and the carb filter. Switching to the other tank changes which fuel pump is on.
>
> A couple months back, I replaced the timing gears with a 4 degree advanced set. At the same time, I changed my vacuum gauge from an elcheapo gauge
> that had a range from 10 to 2 o'clock, to a S&W guage that sweeps from 7 to 5 o'clock. Readings on the vacuum match a large old mechanics vacuum
> gauge that was my Dad's back in the late 30's and has always been very accurate.
>
> When I first started the engine after replacing the timing chains, it had been sitting for a couple months while I replaced the tranny. The motor
> idled like crap. Rough, popping through the carb. It would smooth out as it warmed up but still ran a bit rough. Yes, the modulator vacuum hose is on
> and functioning correctly. I talked to Dick Patterson and went through the timing, dead on 12 degrees with the vacuum adv off and plugged. Verified
> the mechanical advance is working, also verified the vacuum advance is working. Dinked with it a bit over a couple days and things got better as far
> as the idle was concerned but never really changed anything. I moved the timing a degree or two but was at 12 when I started and ended up at 11.
> Backed out the idle screws about 1/4 turn. About this time I drove the coach and noticed the vacuum seemed a bit low. 55 mph steady and level was
> about 10 inches of mercury. Hot idle was about 16.
>
> Talked to Dick again wondering if the advancing the cam timing 4 degrees would effect the vacuum. He said no and thought it was a vacuum leak. I
> dinked with the timing and got it up to about 12 at 55 mph steady and level road. I've checked everything I can for vacuum leaks. New PVC valve,
> removed the booster vac line and plugged it. No change on vacuum gauge. Carb bolts are tight, modulator is hooked up. Everything is capped. The
> fact that I've got 18 at hot idle makes me think it's not a vacuum leak because I'd THINK that a big vacuum leak would show up more at idle than at
> higher RPM?????
>
> Problem #1 is the vacuum level. The coach runs fine. Pulls stronger than before. BUT at 65mph on a level road just pulling against the wind and
> maintaining speed, my vacuum is 7-8. I watched it all the way to Tampa and back. Runs fine, just lower vacuum than I thought it was before. At 55,
> level and steady, I read 12-13. At 65, level and steady but obviously a heavier wind load (don't forget I'm towing too), I'm at 7-8. Btw the toad
> brakes and coach Ebrake are clear and rolling free.
>
> So the question is, what kind of vacuum do you get a 65 level and steady? Dick said since the coach was running fine, I should put a piece of
> electrical tape on the vacuum gauge and just drive it. He might be right but I THINK it was about 5 inches higher before I advanced the cam timing.
> I don't THINK advancing the cam timing should effect the vacuum much if any. If I set the timing for max vacuum, I can get hot idle vacuum up near
> 18-19 but the timing mark is almost out of sight...probably 25-30 degrees of advance and that's with vacuum off and 700 RPM.
>
> Problem #2 is a "cough". Not a backfire, just a 'chu'. Happened a couple times on the way to Tampa and 6-10 more on the way home. Its not much,
> just enough that the wife sometimes asks, "What was that?"
>
> Remember the rough running that seemed to go away right after I got it running again.
>
> One more data point. On the way home, we stopped for lunch and I started the Onan. Ran like crap. Wouldn't come to speed and stabilize enough for
> the automatic transfer switch to turn on the 120. Turned it off and came on home. Now it starts and runs BETTER but still rough, it will at least
> trip the transfer switch on. My buddy Beau thought it was crap in the carb.
>
> I'm wondering if it is water in the tanks? This trip had 1600 miles of buying today's ethanol laced crap. Other than one tank starting out, and a
> stop at a big Shell in Florida (Ken and Stick also filled up there and have reported no problems) all the gas was purchased at big truck stops, Flying
> J, Petro, etc. I'd have thought that any water would have been flushed out,
>
> I've thought about plugged fuel filters. Wide open throttle is no problem and I'd think it would be if there was a partially blocked filter.
>
> It's not repeatable. 10 times in 1600 miles. It SEEMS to happen when I'm transitioning from a level pull or downhill to more throttle at about 2600
> rpm. Just a little 'chuu'. Not a bang, not a pop, not loud, literally sounds like a muffled cough.
>
> So today, I checked the timing again with TWO timing lights. 12 degrees.
>
> Ken Henderson loaned me a wide band O2 sensor and I welded a bung up close to the engine and hooked it up.
> At cold idle (700 rpm) with the choke about closed it read 10.4
> warm idle with half choke was 12.1
> hot idle (hot enough that the oil cooler fan was on so the oil temp was > 180), the ratio was 12.4 climbing to 13.2 as it ran a bit more.
>
> IN PARK (it was getting late and I did not drive it today)
> 700 RPM 13.2
> 1300 RPM 12.0
> 2000 RPM 14.6
> 2500 RPM 15.7
> 3000 RPM 15.9
>
> That's all the data I have.
>
> In summary, I have two issues. They might or might not be related:
>
> 1- Low vacuum? (or perhaps it's just fine???)
> 2- The cough? Water?? Add a couple bottles of denatured alcohol??
>
> Your thoughts, advice, etc are solicited. Please try not to hijack this thread. If you want to talk about something else, please start another
> thread.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76 Eleganza to be re-bodied as an Art Deco car hauler
> _______________________________________________
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> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: A couple 'issues' I'd like some advice on. [message #270905 is a reply to message #270901] |
Sat, 31 January 2015 21:22 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Hi Kerry, seems if your vacuum reading is better when cold might indicate a leak from a joint which would tighten when hot where as a crack would open when hot. I might suggest spraying wd-40 on all bolted or screwed joints while idling and watch the vacuum gauge closely as you do it. Intake gasket, vacuum line fitting threads and where the lines attach like both ends of tranny line, pcv, charcoal canister, check dist adv., choke pull off diaphram, any extra 403 stuff. Try tightening the screws that hold the carb together also. Pull the spark plugs and see if one is darker like maybe sucking from underside of intake gasket.
C. Boyd
76 Crestmont
East Tennessee
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| Re: A couple 'issues' I'd like some advice on. [message #270911 is a reply to message #270901] |
Sat, 31 January 2015 22:11 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Senior Member |
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After my rebuild (Cad 500), I had unusually low vacuum....Similar to what you are experiencing. After checking what seemed like *everything*, I took a needle nose pliers and one at a time pinched off every vacuum hose at the carb and intake manifold. When I got to the *NEW* PCV valve (replaced with the rebuild), the vacuum jumped up about 4 inches. PCV was letting to much air through. Even thought the book said it was the correct PCV, it was obviously wrong. I went back to my local NAPA and sucked on every PCV of the correct size that they had and found one that had very little draw. Put that in and have been running it ever since. 19" vacuum at an idle, 13-16" down the road, flat, no head wind, towing. Try pinching off each vacuum hose, if for no other reason than it is a quick way to verify/eliminate those as the issue. Your little "cough" when transitioning to a little more throttle sounds to me like a lean cough. You should be able to see this on your FA meter when you touch the accelerator. You will see a very brief flash to 16 or 17/1 at the cough. Is your accelerator pump linkage in the correct hole? Should be in the inner one, allowing for more travel in the pump and more fuel to eliminate stumble when going from low to intermediate or high speed circuits....just something else to check.
Low vacuum like you have is not good especially with a carb. The power valve on the "Stock" GMC carb comes in at about 8" which means that at 8" and lower...even at low throttle pressure, you are running excessively rich....most of the time. IMO, your vacuum is lower than it should be...but then maybe putting a piece of black tape over the gauge is perhaps a good solution. 
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: [GMCnet] A couple 'issues' I'd like some advice on. [message #270914 is a reply to message #270901] |
Sat, 31 January 2015 23:02 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Kerry,
I think your hot idle mixture is way too rich. I would turn the idle
mixture screws in, while watching the vacuum gauge to see if
that won't improve things. Also, I'm not criticizing. but is it possible
you got distracted and set the timing chain to the
retarded position instead of advanced. Don't ask why I know this is
possible.
Gary Kosier
77PB w/500 Cad
Newark, Oh
-----Original Message-----
From: Kerry Pinkerton
Sent: Saturday, January 31, 2015 8:56 PM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] A couple 'issues' I'd like some advice on.
I've got a couple things going on and I'd appreciate some wisdom from the
brain trust. I have some ideas but I'm scratching my head.
Some history and then some facts.
77 403 26' pull a Saturn toad and have a Powerdrive and a 3.21 which ends up
as a 3.66 final drive ratio. 65mph is about 3000 RPM.
Motor was rebuilt about 5000 miles back, As of yesterday, compression is
150-165. All but 1 cylinder (#4) is between 165-160. Patterson carb and
distributor with his plugs and wires replace when the engine done. All
electric fuel pumps. Two pumps outside the tanks, filters before each pump,
another filter before the engine, and the carb filter. Switching to the
other tank changes which fuel pump is on.
A couple months back, I replaced the timing gears with a 4 degree advanced
set. At the same time, I changed my vacuum gauge from an elcheapo gauge
that had a range from 10 to 2 o'clock, to a S&W guage that sweeps from 7 to
5 o'clock. Readings on the vacuum match a large old mechanics vacuum
gauge that was my Dad's back in the late 30's and has always been very
accurate.
When I first started the engine after replacing the timing chains, it had
been sitting for a couple months while I replaced the tranny. The motor
idled like crap. Rough, popping through the carb. It would smooth out as it
warmed up but still ran a bit rough. Yes, the modulator vacuum hose is on
and functioning correctly. I talked to Dick Patterson and went through the
timing, dead on 12 degrees with the vacuum adv off and plugged. Verified
the mechanical advance is working, also verified the vacuum advance is
working. Dinked with it a bit over a couple days and things got better as
far
as the idle was concerned but never really changed anything. I moved the
timing a degree or two but was at 12 when I started and ended up at 11.
Backed out the idle screws about 1/4 turn. About this time I drove the
coach and noticed the vacuum seemed a bit low. 55 mph steady and level was
about 10 inches of mercury. Hot idle was about 16.
Talked to Dick again wondering if the advancing the cam timing 4 degrees
would effect the vacuum. He said no and thought it was a vacuum leak. I
dinked with the timing and got it up to about 12 at 55 mph steady and level
road. I've checked everything I can for vacuum leaks. New PVC valve,
removed the booster vac line and plugged it. No change on vacuum gauge.
Carb bolts are tight, modulator is hooked up. Everything is capped. The
fact that I've got 18 at hot idle makes me think it's not a vacuum leak
because I'd THINK that a big vacuum leak would show up more at idle than at
higher RPM?????
Problem #1 is the vacuum level. The coach runs fine. Pulls stronger than
before. BUT at 65mph on a level road just pulling against the wind and
maintaining speed, my vacuum is 7-8. I watched it all the way to Tampa and
back. Runs fine, just lower vacuum than I thought it was before. At 55,
level and steady, I read 12-13. At 65, level and steady but obviously a
heavier wind load (don't forget I'm towing too), I'm at 7-8. Btw the toad
brakes and coach Ebrake are clear and rolling free.
So the question is, what kind of vacuum do you get a 65 level and steady?
Dick said since the coach was running fine, I should put a piece of
electrical tape on the vacuum gauge and just drive it. He might be right
but I THINK it was about 5 inches higher before I advanced the cam timing.
I don't THINK advancing the cam timing should effect the vacuum much if any.
If I set the timing for max vacuum, I can get hot idle vacuum up near
18-19 but the timing mark is almost out of sight...probably 25-30 degrees of
advance and that's with vacuum off and 700 RPM.
Problem #2 is a "cough". Not a backfire, just a 'chu'. Happened a couple
times on the way to Tampa and 6-10 more on the way home. Its not much,
just enough that the wife sometimes asks, "What was that?"
Remember the rough running that seemed to go away right after I got it
running again.
One more data point. On the way home, we stopped for lunch and I started
the Onan. Ran like crap. Wouldn't come to speed and stabilize enough for
the automatic transfer switch to turn on the 120. Turned it off and came on
home. Now it starts and runs BETTER but still rough, it will at least
trip the transfer switch on. My buddy Beau thought it was crap in the carb.
I'm wondering if it is water in the tanks? This trip had 1600 miles of
buying today's ethanol laced crap. Other than one tank starting out, and a
stop at a big Shell in Florida (Ken and Stick also filled up there and have
reported no problems) all the gas was purchased at big truck stops, Flying
J, Petro, etc. I'd have thought that any water would have been flushed
out,
I've thought about plugged fuel filters. Wide open throttle is no problem
and I'd think it would be if there was a partially blocked filter.
It's not repeatable. 10 times in 1600 miles. It SEEMS to happen when I'm
transitioning from a level pull or downhill to more throttle at about 2600
rpm. Just a little 'chuu'. Not a bang, not a pop, not loud, literally
sounds like a muffled cough.
So today, I checked the timing again with TWO timing lights. 12 degrees.
Ken Henderson loaned me a wide band O2 sensor and I welded a bung up close
to the engine and hooked it up.
At cold idle (700 rpm) with the choke about closed it read 10.4
warm idle with half choke was 12.1
hot idle (hot enough that the oil cooler fan was on so the oil temp was >
180), the ratio was 12.4 climbing to 13.2 as it ran a bit more.
IN PARK (it was getting late and I did not drive it today)
700 RPM 13.2
1300 RPM 12.0
2000 RPM 14.6
2500 RPM 15.7
3000 RPM 15.9
That's all the data I have.
In summary, I have two issues. They might or might not be related:
1- Low vacuum? (or perhaps it's just fine???)
2- The cough? Water?? Add a couple bottles of denatured alcohol??
Your thoughts, advice, etc are solicited. Please try not to hijack this
thread. If you want to talk about something else, please start another
thread.
--
Kerry Pinkerton
North Alabama, near Huntsville,
77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76
Eleganza to be re-bodied as an Art Deco car hauler
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] A couple 'issues' I'd like some advice on. [message #270924 is a reply to message #270923] |
Sun, 01 February 2015 01:42 |
appie
Messages: 902
Registered: April 2013
Location: denmark
Karma: 2
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Senior Member |
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Did you read my input about nozzle drip?
Make sure you have anough power T the ignition to make a good spark. You can lay a wire directly from the batteri to the distributor and see what happenes
Who said that 99 procent of carb problems are disttributor problems ?
Appie
eleganza 76 "Olga" now sadly sold
6 wheel discbrake
Quadrabags
Springfield stage 2 462 olds
Manny tranny
( pictures at http://www.gmcmhphotos.com/photos/g6489-olga.html
Fulltiming in Europe july 2014 til july 2016
Denmark
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| Re: [GMCnet] A couple 'issues' I'd like some advice on. [message #270931 is a reply to message #270914] |
Sat, 31 January 2015 23:17 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Kerry, I have a great deal of experience with cam timing. If you advance
the timing, you should notice the vacuum will be higher at a slightly lower
rpm. If you retard it, you should notice the vacuum higher at a slightly
higher one. The maximum vacuum should not be any higher than it would be
with the timing straight up. Unless you have a camshaft that is quite a bit
different than the stock Olds cam. I am just guessing here because I don't
know what cam you indeed have. If you know the spec's, it would help me be
more exact.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Jan 31, 2015 9:02 PM, "Kosier" wrote:
> Kerry,
>
> I think your hot idle mixture is way too rich. I would turn the idle
> mixture screws in, while watching the vacuum gauge to see if
> that won't improve things. Also, I'm not criticizing. but is it possible
> you got distracted and set the timing chain to the
> retarded position instead of advanced. Don't ask why I know this is
> possible.
>
> Gary Kosier
> 77PB w/500 Cad
> Newark, Oh
>
> -----Original Message----- From: Kerry Pinkerton
> Sent: Saturday, January 31, 2015 8:56 PM
> To: gmclist@temp.gmcnet.org
> Subject: [GMCnet] A couple 'issues' I'd like some advice on.
>
> I've got a couple things going on and I'd appreciate some wisdom from the
> brain trust. I have some ideas but I'm scratching my head.
>
> Some history and then some facts.
>
> 77 403 26' pull a Saturn toad and have a Powerdrive and a 3.21 which ends
> up as a 3.66 final drive ratio. 65mph is about 3000 RPM.
>
> Motor was rebuilt about 5000 miles back, As of yesterday, compression is
> 150-165. All but 1 cylinder (#4) is between 165-160. Patterson carb and
> distributor with his plugs and wires replace when the engine done. All
> electric fuel pumps. Two pumps outside the tanks, filters before each pump,
> another filter before the engine, and the carb filter. Switching to the
> other tank changes which fuel pump is on.
>
> A couple months back, I replaced the timing gears with a 4 degree advanced
> set. At the same time, I changed my vacuum gauge from an elcheapo gauge
> that had a range from 10 to 2 o'clock, to a S&W guage that sweeps from 7
> to 5 o'clock. Readings on the vacuum match a large old mechanics vacuum
> gauge that was my Dad's back in the late 30's and has always been very
> accurate.
>
> When I first started the engine after replacing the timing chains, it had
> been sitting for a couple months while I replaced the tranny. The motor
> idled like crap. Rough, popping through the carb. It would smooth out as
> it warmed up but still ran a bit rough. Yes, the modulator vacuum hose is on
> and functioning correctly. I talked to Dick Patterson and went through
> the timing, dead on 12 degrees with the vacuum adv off and plugged.
> Verified
> the mechanical advance is working, also verified the vacuum advance is
> working. Dinked with it a bit over a couple days and things got better as
> far
> as the idle was concerned but never really changed anything. I moved the
> timing a degree or two but was at 12 when I started and ended up at 11.
> Backed out the idle screws about 1/4 turn. About this time I drove the
> coach and noticed the vacuum seemed a bit low. 55 mph steady and level was
> about 10 inches of mercury. Hot idle was about 16.
>
> Talked to Dick again wondering if the advancing the cam timing 4 degrees
> would effect the vacuum. He said no and thought it was a vacuum leak. I
> dinked with the timing and got it up to about 12 at 55 mph steady and
> level road. I've checked everything I can for vacuum leaks. New PVC valve,
> removed the booster vac line and plugged it. No change on vacuum gauge.
> Carb bolts are tight, modulator is hooked up. Everything is capped. The
> fact that I've got 18 at hot idle makes me think it's not a vacuum leak
> because I'd THINK that a big vacuum leak would show up more at idle than at
> higher RPM?????
>
> Problem #1 is the vacuum level. The coach runs fine. Pulls stronger than
> before. BUT at 65mph on a level road just pulling against the wind and
> maintaining speed, my vacuum is 7-8. I watched it all the way to Tampa
> and back. Runs fine, just lower vacuum than I thought it was before. At
> 55,
> level and steady, I read 12-13. At 65, level and steady but obviously a
> heavier wind load (don't forget I'm towing too), I'm at 7-8. Btw the toad
> brakes and coach Ebrake are clear and rolling free.
>
> So the question is, what kind of vacuum do you get a 65 level and steady?
> Dick said since the coach was running fine, I should put a piece of
> electrical tape on the vacuum gauge and just drive it. He might be right
> but I THINK it was about 5 inches higher before I advanced the cam timing.
> I don't THINK advancing the cam timing should effect the vacuum much if
> any. If I set the timing for max vacuum, I can get hot idle vacuum up near
> 18-19 but the timing mark is almost out of sight...probably 25-30 degrees
> of advance and that's with vacuum off and 700 RPM.
>
> Problem #2 is a "cough". Not a backfire, just a 'chu'. Happened a couple
> times on the way to Tampa and 6-10 more on the way home. Its not much,
> just enough that the wife sometimes asks, "What was that?"
>
> Remember the rough running that seemed to go away right after I got it
> running again.
>
> One more data point. On the way home, we stopped for lunch and I started
> the Onan. Ran like crap. Wouldn't come to speed and stabilize enough for
> the automatic transfer switch to turn on the 120. Turned it off and came
> on home. Now it starts and runs BETTER but still rough, it will at least
> trip the transfer switch on. My buddy Beau thought it was crap in the
> carb.
>
> I'm wondering if it is water in the tanks? This trip had 1600 miles of
> buying today's ethanol laced crap. Other than one tank starting out, and a
> stop at a big Shell in Florida (Ken and Stick also filled up there and
> have reported no problems) all the gas was purchased at big truck stops,
> Flying
> J, Petro, etc. I'd have thought that any water would have been flushed
> out,
>
> I've thought about plugged fuel filters. Wide open throttle is no problem
> and I'd think it would be if there was a partially blocked filter.
>
> It's not repeatable. 10 times in 1600 miles. It SEEMS to happen when I'm
> transitioning from a level pull or downhill to more throttle at about 2600
> rpm. Just a little 'chuu'. Not a bang, not a pop, not loud, literally
> sounds like a muffled cough.
>
> So today, I checked the timing again with TWO timing lights. 12 degrees.
>
> Ken Henderson loaned me a wide band O2 sensor and I welded a bung up close
> to the engine and hooked it up.
> At cold idle (700 rpm) with the choke about closed it read 10.4
> warm idle with half choke was 12.1
> hot idle (hot enough that the oil cooler fan was on so the oil temp was >
> 180), the ratio was 12.4 climbing to 13.2 as it ran a bit more.
>
> IN PARK (it was getting late and I did not drive it today)
> 700 RPM 13.2
> 1300 RPM 12.0
> 2000 RPM 14.6
> 2500 RPM 15.7
> 3000 RPM 15.9
>
> That's all the data I have.
>
> In summary, I have two issues. They might or might not be related:
>
> 1- Low vacuum? (or perhaps it's just fine???)
> 2- The cough? Water?? Add a couple bottles of denatured alcohol??
>
> Your thoughts, advice, etc are solicited. Please try not to hijack this
> thread. If you want to talk about something else, please start another
> thread.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76
> Eleganza to be re-bodied as an Art Deco car hauler
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| Re: A couple 'issues' I'd like some advice on. [message #270941 is a reply to message #270901] |
Sun, 01 February 2015 09:05 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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Chuck, I have not yet done the aerosol spray test for vacuum leaks, I will do that tomorrow as well as Larry's pinch test. Weather is going to be crappy today.
The plugs are new Bosch Platinum that Dick P recommended. I forget the gap. When I did the compression test, all the plugs looked good. A nice tan shade.
Running off another fuel source isn't really feasible. It might not happen in 200 miles.
Appie, I'll check the voltage on the distributor wire. The module might cause the cough but not the vacuum issue. I'm thinking they may be related....or not...  
Kosier wrote on Sat, 31 January 2015 23:02I think your hot idle mixture is way too rich. I would turn the idle mixture screws in, while watching the vacuum gauge to see if
that won't improve things.
I was wondering the same thing Gary and was reading up on understanding Air Fuel Ratios last night.
Kosier wrote on Sat, 31 January 2015 23:02 ... but is it possible you got distracted and set the timing chain to the retarded position instead of advanced....
Well I hope not Gary but I'll be honest, I'm not 100% sure now. I certainly THOUGHT I matched the right simbols on the gears. I wish I had taken a photograph.
James Hupy wrote on Sat, 31 January 2015 23:17Kerry, I have a great deal of experience with cam timing. If you advance the timing, you should notice the vacuum will be higher at a slightly lower
rpm. If you retard it, you should notice the vacuum higher at a slightly
higher one. The maximum vacuum should not be any higher than it would be
with the timing straight up. Unless you have a camshaft that is quite a bit
different than the stock Olds cam. I am just guessing here because I don't
know what cam you indeed have. If you know the spec's, it would help me be
more exact....
Jim and Gary, I appreciate your 'been there-done that' insight. The engine has the stock 403 cam. There is less than 70K miles on the engine and less than 5K since the overhaul. I am 'almost' sure the cam is in right...almost. But that almost is driving me nuts to the point. Almost to the point that I will pull the timing cover off to check.
Jim, your explanation of the vacuum readings is exactly what I expected. I contacted Jerry Work who has an advanced cam in his motor and he told me that they did nothing to the engine/carb/distributor. Basically just lowered the torque curve...free power.
The engine FEELS stronger but now I'm not sure. Dick P told me that the engine would feel very flat if I had gotten it backward and it's definitely not that. Running 65-70 is no problem and she climbed the hills in North Alabama just fine.
Is there an way to check the timing without pulling the timing cover off?
I appreciate everyone's thoughts and inputs.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: A couple 'issues' I'd like some advice on. [message #270944 is a reply to message #270943] |
Sun, 01 February 2015 09:55 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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C Boyd wrote on Sun, 01 February 2015 09:27Kerry, a tdc indicator and a degree wheel should tell you where your timing is.
But don't I still need to get to the cam to use the degree wheel? TDC is easy because of the timing mark on the new harmonic balancer. I guess I COULD pull the valve cover put a dial gauge on the rocker arms of #1 but honestly if the consensus is that the installation could be off, I'll just pull the front off the engine and check/fix. It's only a day and now that I've split the fan shroud, I can actually get up there easier and see what I'm doing with the timing gears. When I put them in, the shroud was in one piece and it was harder to see.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: A couple 'issues' I'd like some advice on. [message #271002 is a reply to message #270990] |
Sun, 01 February 2015 23:48 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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After re-reading, I notice you said ALL of the cylinders were at 160-165 except #4. Since this is a relatively new engine, I would not be expecting that greater than 10% drop on just one cylinder. Maybe there is a lifter that is malfunctioning (deflating)once in awhile, giving you that cough you mentioned. For example, if the exhaust valve doesn't get opened on one cycle, there will be residual pressure in the cylinder when the intake valve opens in the next cycle.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: A couple 'issues' I'd like some advice on. [message #271004 is a reply to message #270901] |
Mon, 02 February 2015 02:20 |
Gadabout
Messages: 124
Registered: March 2013
Location: Edmonton
Karma: 2
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Senior Member |
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Changing cam timing will often result in a change in engine vacuum, this is not necessarily a bad thing, providing you are happy with performance.
As your baseline for vacuum was established prior to the change in cam timing, the vacuum reading after the cam change now represents the new baseline for tuning.
If an RV Cam was installed during the rebuild, it should have a grind that provides high torque at low RPM. Some custom grinds have advance built in.
As others have already suggested, use a degree wheel to verify the cam settings.
Before pulling everything apart, check your timing indicator to make sure it was not bent while doing work on the engine. If it was, you will be getting a false reading on ignition timing . If it looks good, you should still use a degree wheel to verify it is reading correct at TDC.
Good luck and let's us know if you find the answer....
Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
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| Re: A couple 'issues' I'd like some advice on. [message #271016 is a reply to message #270901] |
Mon, 02 February 2015 09:00 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Kerry -
A quick n dirty TDC meter. Destroy a sparkplug by grinding out all the ceramic. Weld a nipple to the remaining shell. Slip a piece of clear tubing over the nipple. Now you can remove the plug from the No 1 cylinder, install the meter, and turn the engine close to tdc. Fill the opening with engine oil through the tube, and then rock the shaft across TDC and back. Highest level in the tube is TDC. When you're done, use your brake vacuum hand pump and tube to remove the oil as much as you can. It's gonna smoke when you restart it.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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