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| Sputter n choke [message #251953] |
Wed, 11 June 2014 11:28  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, it isn't a sputter, it's a quit. When it's hot, my coach quits - or tries to - when shifting. I found out yesterday, I can >usually< nurse it back to life with the accelerator pump but not always. This is the syndrome which put me beside the road on the way to Louisville. I redid the fuel feed, but going over the mountains, it quit on the way to Bean Station. Once cooled off, it took it on in. Now, it just doesn't want to run when it's warm and shifting. The temp gauge runs square on the quarter mark in the summer, this is up a bit. Last year, it hit nearly half going over Monteagle but gave no problems and went down on the downhill side. Also went down going to BS coming down the backside of the hill, which makes me think the cooling system is working. Both times it's quit, I pull the fuel line to the pump input, nothing there. Interestingly, the output line pulses when the engine's running. Going to Louisville, I pulled the air cleaner and pumped, no gas in the carb, but clear filter.
My thoughts are, it's vapor locking back down the line someplace, or the carb is getting so hot the pressure sends fuel back towards the tank. Or the pump is dying, or the ignition module gets too hot. I am however open to other ideas.
This weekend is committed to getting my 'travel truck' engine installed and it running. The toad isn't really a good commuter, it's missing many of the amenities like A/C, an automatic, etc. Once it's going, the GMC will get the tanks pulled out and checked, a new fuel pump, and a new ignition module. I'll keep the current module as a spare. Hopefully, all of this will highlight whatever's making the thing quit running.
--johnny
'76 23' transmode norris
Braselton ga
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: [GMCnet] Sputter n choke [message #251955 is a reply to message #251953] |
Wed, 11 June 2014 11:35  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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read here
http://www.gmcmhphotos.com/photos/data/4634/TANK_VENTS1.pdf
erf
On Wed, Jun 11, 2014 at 9:28 AM, Johnny Bridges wrote:
> Well, it isn't a sputter, it's a quit. When it's hot, my coach quits - or
> tries to - when shifting. I found out yesterday, I can >usually< nurse it
> back to life with the accelerator pump but not always. This is the
> syndrome which put me beside the road on the way to Louisville. I redid the
> fuel
> feed, but going over the mountains, it quit on the way to Bean Station.
> Once cooled off, it took it on in. Now, it just doesn't want to run when
> it's
> warm and shifting. The temp gauge runs square on the quarter mark in the
> summer, this is up a bit. Last year, it hit nearly half going over
> Monteagle but gave no problems and went down on the downhill side. Also
> went down going to BS coming down the backside of the hill, which makes me
> think the cooling system is working. Both times it's quit, I pull the
> fuel line to the pump input, nothing there. Interestingly, the output line
> pulses when the engine's running. Going to Louisville, I pulled the air
> cleaner and pumped, no gas in the carb, but clear filter.
> My thoughts are, it's vapor locking back down the line someplace, or the
> carb is getting so hot the pressure sends fuel back towards the tank. Or
> the
> pump is dying, or the ignition module gets too hot. I am however open to
> other ideas.
> This weekend is committed to getting my 'travel truck' engine installed
> and it running. The toad isn't really a good commuter, it's missing many of
> the amenities like A/C, an automatic, etc. Once it's going, the GMC will
> get the tanks pulled out and checked, a new fuel pump, and a new ignition
> module. I'll keep the current module as a spare. Hopefully, all of this
> will highlight whatever's making the thing quit running.
>
> --johnny
> '76 23' transmode norris
> Braselton ga
>
> --
> "Sometimes I wonder what tomorrow's gonna bring when I think about my
> dirty life and times" --Warren Zevon
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
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: Sputter n choke [message #251962 is a reply to message #251953] |
Wed, 11 June 2014 12:25 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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When I put a new mechanical fuel pump on mine, it made a world of difference with vapor lock.
I've been told that removing the gas cap can sometimes help (hopefully it won't spit gas out).
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Sputter n choke [message #251964 is a reply to message #251953] |
Wed, 11 June 2014 13:03 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Although you could have other problems as well, it is obvious that you fave a fuel starvation problem. It could be as simple as having winter formulated gas in your tanks, which doesn't do well in high temps. It also could be plugged up fuel socks in your tanks. You can blow them out with compressed air, just make sure your gas cap is off. It also could be a crack in a fuel hose, allowing air to be sucked into the line by your mechanical pump. Your fuel pump may be getting weak as well.
I had severe fuel starvation issues when I first got my coach although it never actually died. I changed the carburetor filter and installed a Mr Gasket heat dissipator under the carb. Both these things helped a lot, but the one thing that helped the most was the addition of an electric fuel pump back by the tanks. I used a solenoid type pump and installed it between the tank and the fuel selector valve in the aux tank line. I powered it off the fuel tank valve so that when I experience fuel starvation, I can switch to the aux tank, the pump turns on and clears up the problem. To do it right, and safely, I guess it is a good idea to add an oil pressure switch to the circuit so the pump is disabled when you run out of oil pressure in case of an accident. I didn't do that but may add that feature someday.
Just this last weekend, I got under there and replaced the five year old electric pump with a new one, and changed the in line fuel filters I had added. The original pump I had installed was for a 5/16" fuel line and, even though it was rated at the same volume as a 3/8" one, I felt like the slight restriction was not helping. The new pump is a 3/8". Before I started, I disconnected the downstream filter and pumped some gas into a jar. I did the same thing after changing out the pump and the filters and the new pump appeared to be pumping quite a bit more gas than the old one. A purely unscientific observation, I know, but it seemed pretty obvious that was the case. We will see how much better this new pump works when we take our next trip in July.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Sputter n choke [message #251968 is a reply to message #251953] |
Wed, 11 June 2014 14:06 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I've gotten no spit on the fuel cap since I first brought it home. The cap vent operates under suction.
I called myself looking at the vents. None seem to be compromised, but it is slow to fill. I have a problem wondering why if there's a vent problem it only shows itself when shifting to a lower engine speed and whe3n the engine is hot. Being as Emery brought it up, I'll check them again.
I'm minded to tee my MagneHelix in the vent line and see what's going on with it.
Keep watching this space...
--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: Sputter n choke [message #251977 is a reply to message #251953] |
Wed, 11 June 2014 15:14 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Vapor lock would be at the top of my list. If you don't have an electric pump at least put one in the aux line .
Roy Keen
Minden,NV
76 X Glenbrook
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