Fuel pressure regulator changed, ecm changed, fuel pump working, fuses checked. Truck engine will try to turn over, sometimes it will start, but only after trying several times, mostly it won't start. Could problem be in the ignition switch? Please help, very frustrated!
The oil presure switch does have some bearing on the problem but my suggestion is to change the coil. I had a the same problem with an astro van. I changed everything that you have described and it fixed the problem just for a little while and then all of a sudden did it again. I changed the coild and the cold start swithch and never had the problem again.
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Probably the fuel pump. When you stand outside the vehicle and turn the ignition on, you should hear the pump in the fuel tank working for a few seconds - if not, there is a problem with the pump, the pump relay, the fuse, etc. You can also check the pump fuel pressure with a gauge attached to the service port on the fuel line at the back of the engine (caution - use an approved gauge and hookup!).
If the pump is working, check the fuel filter for plugging. The problem can also be caused by a faulty fuel regulator (inside the upper manifold).
What is the fuel pressure? these trucks need a certain amount of pressure to start, if low just 3psi it will not start, if you are sure the pump is good then you may bad spider injector. check fuel pressure first and also try spraying starting fluid into throttle body and see if truck starts. the pump needs 60 -66 psi to start the truck.
The pump is powered by the relay. The relay is grounded by the computer. It gets a ground signal for the first 3 seconds, then only if the computer sees oil pressure or RPM to know the engine is running. You should be able to ground the relay and run the pump for several minutes. After 30 seconds you should be at max pressure. Normal pressure is 15psi for a truck that has throttle body injectors such as a mid 80s model, and 65psi for trucks that have port fuel injection like yours. You may have the wrong pump.
Sounds to me like either your pressure regulator is bad or you have a loose fitting somewhere in the fuel line from the fuel pump to the engine. When you turn your key to the on position, you should hear the whine of the fuel pump until it builds pressure. When you shut the truck off the pressure regulator should retain the pressure for a certain amount of time but if it don't close then air is allowed into the fuel line and the fuel drains down to fuel line away from the engine. Next time you try and start the truck after it has sat for a while try turning the key on until you hear the fuel pump whine shut off, then repeat it 3-5 times and then try to start it. Basically that is running the pump enough to get the fuel back up to the injectors. Check for loose fittings in the fuel line, or cracks in the fuel line and if all that is fine then replace the regulator.
If no check engine light is on, I would check the ign-distributor cap and rotor, also check the crank and crank sensor. There is also a ign-mod located in the distributor assembly under the rotor. They will fail when hot.
i had the same problem and replaced the fuel pressure regulator. Cost about $45 at advance auto store or about $90 at napa auto stores. Once i replace that my truck started right yup and runs like a champ
the fuel pressure if leaking could cause this the regulator is located under the intake plenum but you should smell gas .if you dont then most likely the pump is bad ,the pump will come on for 2 seconds when the key is on then go off it will not stay on with just the key on only when you crank it will it .so have your fuel pressure checked with a gauge.
When you hook the pressure test guage to shrader valve on fuel rail what it reads is what the pressure is from pump, around 60 p.s.i. all you need to do is hook up the guage and turn on key, you do not have to turn engine over, and if pump is good it will shoot up to 58 or 60 right now.