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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hey guys. Been dealing with this for about a year now. I have a 1988 IROC-Z with the LB9 engine that is difficult to start when cold. What happens is that I crank the engine for a few seconds and it doesn't start, and then when I try again it'll catch, idle poorly for a few seconds and then eventually run and drive normally. One thing I've noticed is that it won't catch until the oil pressure gauge goes to 30ish PSI.
Although the car usually starts normally when it's warmed up, yesterday it did not and refused to catch. In this case, the oil pressure never went to the 30 PSI mark and stayed fluttering at the bottom of the gauge.
Things I've checked:
Spark plugs are good
Fuel pressure is good
Fuel pump is about six months old
Fuel filter is about six months old
Timing is dead on
What's the fuel pressure cold when you turn on the key only? Could be a bad fuel pump relay and the pump isn't getting power till the oil pressure switch comes in. See diagram. Check your pressure stone cold and test your relay.
i have the exact same problem, i hear the fuel pump when turn key on, i get full 42PSI pressure when cranking, it finally starts once the manual oil pressure gauge goes above 0, usually three to four long cranks
would love to get this fixed, can the oil pressure switch be causing this? I ask as i do remember replacing it a few years back, i know it was not a genuine part, rather a china made special
It's not impossible, but unlikely. As soon as the ECM detects distributor pulses (even from cranking) it will energize the fuel pump relay. I might be more suspicious of the FPR or something else bleeding off rail pressure too quickly.
I might be more suspicious of the FPR or something else bleeding off rail pressure too quickly.
If the pressure didn't fully raise up on the first key turn then I was going to question the hose (or damper) that's between the pump and the fuel line of the sending unit. The oil pressure information was the only reason I gave the diagram and questioned the relay.
my pressure does not hold, stays steady while cranking, but drops to 0 right awaw, i have replaced the FPR and the injectors, the injectors were not from south bay, my bad. is it possible that its the injectors?
once it starts i can shut off and it will start right up, if i left it sit for an hour or so it will be hard to start again, another odd thing, in the winter, if i go out to start the car in the garage, it will fire right up, least did last winter, i will try tonight and see
11-29-2020, 06:49 PM
