1977 98 - cold starts fine then dies completely!

Old June 6th, 2005, 07:59 PM
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Location: Southern Indiana, USA
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1977 98 Regency with stock Olds 350 and stock M4MC Quadrajet, 77K miles.

Carb rebuilt, fuel filter replaced, fuel pump replaced, lines checked, no apparent leaks, new rubber hoses, engine strong (no smoke), car well maintained.

About every 4th or 5th time, car will start up fine, and idle at normal fast idle speed, AND THEN either a minute or so after starting OR after pulling out from stopped position, car will stall and die. Nothing can be done to get a restart - no closed throttle, pumped or floored. - EXCEPT BY "PRIMIMG" - see below!

****Clue #1: No fuel found in accellerator pump upon immediate inspection of carb at time of stalling. (That is why I did all the above repairs.)

When I rebuilt the carb, I cleaned it and found little evedence of dirt and no evedence of prior rebuild. I replaced needle and seat, and tripple checked smooth operation and float level, and check ball, and all gaskets, and did not see any OBVIOUS evedence of any internal leaks (Main discharge tube plugs seem to be a problem?), and used specs found in 1977 Olds Shop Manual

One other possibility I have seen is the "Siphon break passages" (may not be applicable to this MY car) and also, the vacuum breaks APPEAR to hold vacuum and function with a gradual (2 sec or so) return when vacuum is released. All vacuum hoses have been replaced on carb, and all others EMISSION hoses (cannister, EGR, THERMAC, DTVS,) are plugged. Timing is about correct (advanced to slight pinging at WOT under load) , plugs wires and cap/rotor are new. Weights were rusty but are free.

****Clue #2: If I pour raw gas down the primary (a desperation move the first time this happened) THE CAR WILL START!!!! AND RUN FINE FOREVER!! Ocasionally I need to ""prime"" it twice to get it to stay running.

This has been happening for months now (winter and summer) and there is no pattern to it except with a cold engine and to pour raw gas down carb to get it to run!



BTW, yea that was me in December 2004 - same car same problem..... Just stranded me finally - am now getting really frustrated!
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Old July 29th, 2005, 09:40 AM
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Mark, it may not be fuel delivery problem, it may be a warped baseplate and/or ripped baseplate gasket. With that condition you may draw excessive air intermittently for no apparent reason. Worn throttle bushings can do that too. If your car is idleing or running at part throttle happily and all of a sudden it leans out it can stumble and starve that way and not be a fuel delivery problem (except for lack of negative pressure in the venturi, hence no fuel). I might be way off base but just trying to help. Sorry for the delay in answering but haven't been here lately what with the server problems and such. Good luck.
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Old October 22nd, 2005, 09:27 AM
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It could indeed be a leaning condition caused by a sticking PCV valve, or other vacuum takeoff from the carb or manifold that is leaking. Even power brake boosters can cause huge vacuum leaks.
Try eliminating potential vacuum leaks one by one by plugging them. I know these intermittent problems are difficult to solve. I mentioned before that I had a stalling problem on my Olds caused by a choke that was too rich, and a vacuum pulloff that wasn't working. The combination caused the choke plate to close , and stalled the engine, and would not restart until I stuck a screwdriver into the carb to keep the choke plate open until it warmed up.

Your statement that the acclerator pump well is empty is interesting, since it implies that the float chamber is empty too. Double check that to make sure the jets are above the fuel level, since I've been fooled by looking into the accelerator pump well.

I had two problems with fuel filters that are worth passing on. The first was an aftermarket filter that had too fine an element, and clogged after only a few miles of driving. If the engine sat for a few minutes, it would restart but then stall again a few miles down the road. Switching to a name brand filter solved the problem.

The second problem was stranger by far. It was a fuel starvation problem that would begin only minutes after cleaning and reinstalling the carburetor. Some sort of fine contaminant from the fuel tank was going through the stock inlet fuel filter, but was then accumulating in the carburetor and plugging the idle system. I would find the fine white particles in the bottom of the float bowl. I solved the problem by installing an aftermarket spin-on remote fuel filter designed for diesel trucks, with a 5 micron rating. Tractor supply stores usually stock those filters.

I suppose it's also possible that your fuel pump is faulty. Install a fuel pressure gauge in a "T" fitting in the line at the carb inlet.
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Old November 14th, 2005, 09:13 PM
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I had a 76 Chevy pickup do the here some time ago. It was that the float was sticking in the up position every now and then. Replaced the needle and seat and made sure nothing was bent and it was fine after.
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