Home » Public Forums » GMCnet » Occasional stall
Occasional stall [message #268617] |
Thu, 01 January 2015 09:42 |
jhbridges
Messages: 8412 Registered: May 2011 Location: Braselton ga
Karma: -74
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Now and again, usually after some freeway mileage, my coach will stall when starting from a stop sign or light. Symptom is, it pulls off OK, then - usually when it shifts to second - it simply quits. Sometimes a bit of a sputter, but usually just croaks. Sometimes it restarts immediately, others it takes five - fifteen minutes. When it restarts, it seems to go OK. I've installed an electric pump in the reserve line, hitting it doesn't seem to matter. The pump does help in other situations, heating on hills or idling in traffic, and priming to crank after it's been sitting for a week or two. I have a new and tested coil/module/cap which I think I will install. I'm also contemplating a second electric fuel pump and removing the selector valve. These are Mr Gasket pumps, with internal check valves. They're made for continuous duty for carbureted engines. I detest intermittent troubles (which the GMC seems to generate) because you really can't say "I found thus and such, did this, and fixed 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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Re: Occasional stall [message #268621 is a reply to message #268617] |
Thu, 01 January 2015 11:23 |
George Beckman
Messages: 1085 Registered: October 2008 Location: Colfax, CA
Karma: 11
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Johnny Bridges wrote on Thu, 01 January 2015 07:42Now and again, usually after some freeway mileage, my coach will stall when starting from a stop sign or light. Symptom is, it pulls off OK, then - usually when it shifts to second - it simply quits. Sometimes a bit of a sputter, but usually just croaks. Sometimes it restarts immediately, others it takes five - fifteen minutes. When it restarts, it seems to go OK. I've installed an electric pump in the reserve line, hitting it doesn't seem to matter. The pump does help in other situations, heating on hills or idling in traffic, and priming to crank after it's been sitting for a week or two. I have a new and tested coil/module/cap which I think I will install. I'm also contemplating a second electric fuel pump and removing the selector valve. These are Mr Gasket pumps, with internal check valves. They're made for continuous duty for carbureted engines. I detest intermittent troubles (which the GMC seems to generate) because you really can't say "I found thus and such, did this, and fixed it".
--johnny
Sounds like you have done much of what should fix these annoyances. I had a stall about 30 seconds to one minute after starting for a couple of years. It rarely happened. I have EFI and figured something was amiss with my wiring, etc. Of course as soon as I reworked a connection or something, it ran fine.
Turned out to be the module. Key off, key on usually fixed it but I was along the road for 20 minutes one time. The goofy thing was that it would sometimes work for months just fine, only to rear its ugly head again later.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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Re: Occasional stall [message #268622 is a reply to message #268617] |
Thu, 01 January 2015 11:28 |
Gadabout
Messages: 124 Registered: March 2013 Location: Edmonton
Karma: 2
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Johnny, you appear confident that it is not vapor lock , and I assume you checked the easy stuff such as the PCV , vacuum lines, etc.
My first guess is carb related problems . ( assuming you have a carb and not EFI)
One possibility is fuel loading while idling, then when you start to accelerate , the accelerator pump deliverers even more fuel causing a flood condition. The plugs and intake manifold are now gas soaked requiring time to dry out.
A Defective float or needle and seat or Choke, will lead to fuel loading at idle. To check, heat up the engine , leave it running and remove the air cleaner. Make sure the choke has fully opened, them Look in the carb and see if you notice raw fuel dripping into the intake.
Of course the opposite may also be true, if your accelerator pump is not working then you would be starving for fuel on acceleration, but this would not explain the time it takes to restarts, a few pumps on the pedal and it should start up.
Here is some good info on carb related problems http://www.aa1car.com/library/carburetor.htm
Other possibilities are ignition coil, cracked distributor cap, rotor, these can all be affected by heat soaking when at idle.
Good luck, and let's us know what the problem turns out to be once you find the cure....
Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
[Updated on: Thu, 01 January 2015 11:37] Report message to a moderator
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Re: Occasional stall [message #268628 is a reply to message #268617] |
Thu, 01 January 2015 11:51 |
roy1
Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
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As soon as it shuts down and you are on the side of the road you should look in the carb and see if gas squirts out of the primary venturies when you pump the gas pedal. The next thing if that works is pull a plug wire crank the motor and see if you get a good spark to ground. At least you will now know if you have a fuel or electrical malfunction .
Roy Keen
Minden,NV
76 X Glenbrook
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Re: Occasional stall [message #268635 is a reply to message #268617] |
Thu, 01 January 2015 12:44 |
jhbridges
Messages: 8412 Registered: May 2011 Location: Braselton ga
Karma: -74
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Senior Member |
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Thanks, I'll look for fuel loading. Hadn't thought of that. Went to Orlando flawlessly. Came back flawlessly, till I got off the freeway down the highway from home, and quit coming off the light. Started right back up that time and drove on home.
I'll check the choke as well, tho' it seems to work correctly on warmup. It's the stock setup.
--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
[Updated on: Thu, 01 January 2015 12:47] Report message to a moderator
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