06-13-2010, 02:08 PM
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10mm MW
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Join Date: Sep 2008
Location: Michigan
Posts: 794
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Quote:
Originally Posted by Ferdman
OM616, consider replacing the fuel pump check valve. If the system pressure bleeds off it's possible the hot engine compartment could cause vapor lock in the fuel line.
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Tested that when I went through the fuel system. I was actually surprised how long the system will hold pressure. I let it set for 6 hours and there was still 75% of the running pressure present. I did mention above that the fuel system should be working correctly first. The needs of these cars like people change as they age. The minor electrical, mostly mechanical system does was not designed to adapt to the changing needs as the result of age and use.
At its best, 9 times out of 10, the engine would start the first try, however they often were 3 to 4 second long tries. I mean right when you would normally give up and stop cranking, if you waited another second it would catch. If it didn't, it would on the second try usually with some petal input. Sometimes it will sputter enough for you to let off the starter, but will not keep running. In all cases where starting is marginal, the fuel mixture is too lean IMO.
Starting usually requires a slightly richer fuel mixture which depends on the amount of remaining fuel vapors and the temperature of the block, heads, and the intake air temperature.
Additionally, the engine is worn and dose not pull as low of a vacuum during cranking as it did when it was new. The fuel system has to be compensated for the intake manifold vacuum trying to suck the fuel out of the injectors. Changes in vacuum levels affect the pressure drop at the injectors which has an effect on how willing the injector is to pass fuel in a sufficient quantity.
My mom often likes to take the car to outings and even though she is checked out on the starting procedure, I still worry if it will start for her. Now it starts like an EFI system, every time, with out hesitation. I checked and I am only rapid firing the start injector for 750 milliseconds. Just enough to give it a shot in the butt.
Last edited by OM616; 06-14-2010 at 01:30 PM.
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