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Problems with carburetor?
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DGG
New User
Jul 26, 2012, 2:32 PM
Post #1 of 4
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Problems with carburetor?
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Hello, my wife and I recently purchased a 1988 Winnebago with a Chevy engine. It's a G30, engine size 350. It had problems right form the beginning, but we thought if we had a few repairs done, they would be solved. Well, thousands of dollars later, we're still plugging away and every mechanic seems to have a different take on the matter. The problems are: (1) Usually -but not always - very hard to start. (2) Diesels badly almost every time we turn it off (3) Backfires - usually just when we turn it off, but sometimes when driving. Here's what we've done so far: (1) Replaced fuel pump (2) Replaced carburetor (3) Tune-up (4) Replaced ignition coil (5) Had timing set on distributor and on carburetor several times -- but one mechanic said, "it's not the carburetor's fault, it's just the way these engines are made", whatever that means. (6) Had vacuum hoses re-done. One mechanic said they were hooked up in a really weird fashion, and so he adjusted them, and it did make a difference. He figured that since we bought the vehicle on the West Coast, someone had tinkered with the hoses to make it pass smog inspection.
All of these repairs helped SOME, and it's running much better than it did. But dieseling and hard starting are still a problem - the backfiring occurs only occasionally now, and is mild, compared to the constant severe backfiring when we first got it. And there is often a smell of gas after we turn it off, indicating (I suppose) that it's been flooding. (I've checked for gas leaks, and at one point there actually was one, but I corrected it. But still smell gas.) The new carburetor, by the way, is an Edelbrock - I have the old carburetor and am thinking I might get it rebuilt and reinstalled at some point. After it was replaced, I drove about 2000 miles before I realized that there was then no fuel filter at all on the vehicle, since the old carburetor had a filter in it, and the new one doesn't, and apparently the mechanic didn't think to install a filter somewhere else. I put a filter on myself, and hopefully did so before sediment in the gas caused any damage. Any thoughts about what to do next?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 26, 2012, 3:10 PM
Post #2 of 4
(2069 views)
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Re: Problems with carburetor?
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Should have fixed the OE Quadrajet carb IMO as now it's a bit unknown to me anyway if it can be adjusted at all for this application?
The Quad should have had a set "stall" idle speed and raised when key is in run position to the acceptable idle. Not surprised about hard to start as very hard working gasoline, carbed engines did used to evaporate out the fuel in the carb if engine was shut down fully warmed up - really all warmed up.
Not all did that and you could get a fuel filter that only allowed fuel flow one way which could help. In some 80's less HD trucks I did have troubles with old fashioned vapor lock as metal fuel line from pump to carb was too close to hot engine and re-routing it away solved those.
No fuel filter for that time, even if just short was a mistake. No telling what could be in the carb now. Still there should be a stall idle speed and another either electric or vacuum present (as it would if running) to hold idle up then fall so low it wouldn't like to run-on or "diesel" as you called it.
Could also have hot spots (carbon build up) that would usually clear out with a good run which it's had.
Will it quit the dieseling if you turn off in gear? Try if practical to just start the engine after a cool down for just a minute and if the issue was fuel evaporating out it would stay longer when cool/cold.
This was the fussy crap of late carbs but workable.
Seems the trouble now is a late carb and finding techs that dealt with their crap still working out there. Being in a motor home now would likely take some special adjustments as I'm not so sure the chassis/drivetrain could know exactly what loads were about to happen to it new,
T
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DGG
New User
Jul 26, 2012, 3:15 PM
Post #3 of 4
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Re: Problems with carburetor?
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We did start turning it off in gear after one mechanic suggested it, and that stopped the dieseling MOST of the time, but it still does it a little sometimes even in gear.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 26, 2012, 4:06 PM
Post #4 of 4
(2055 views)
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Re: Problems with carburetor?
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It is going to need carb set (if this one can) to stall out without ignition on. You need someone who can deal with some off normal conditions a carb is in for this,
T
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