First start of morning cranks,sputters,after multiple cranks starts and runs fine rest of day.fuel pressure holds @ 60psi until you start to crank, then immediately drops to 45psi, runs at 60 to 75psi depending on load. one strange thing,the pump primes with key on, and when cranking but also primes when you turn key off?.replaced plugs, fuel filter,coolant sensor.
Check air mass sensor
To assure that it is your main fault.
You can unplug it at morning then start the car if it started well you can change it .if didnt start well then you have to check something else.
Check fuel pressure regulator
I would be checking to see why there is power to the pump with the ignition off as this is a source to flat battery overnight.. May be a relay is still activated by a power source other than the ignition.
SOURCE: 97 suburban, 454, 4x4 hard starting.takes a
may have a bad inj . doese it blow black smoke when irt starts.??
SOURCE: Hard starting Chev 2500HD 8.1 L
i have had the same problem.the solution is the fuel pump! i know you got pressure and it runs so how can it be the fuel pump? the pump is losing its prime you are getting pressure just no volume thats why its crank off crank off the system is priming itself again kinda like a weedeater or similar motor fuel is there just not enough of it to the injector To check this hook a pressure gauge turn on key turn off key release fuel should be plenty but if tis just a few drops thats it hope this helps
SOURCE: 1998 camaro I have replace the fuel pump and
its not your crank sensor its your starter. i just went through the same thing. i have a 1998 chevy camaro 350 lt1. if thats not it its in your stering colum
SOURCE: 1997 Chev Cavalier hard starting
it sounds like the check valve in the fuel pump is letting the fuel bleed back into the tank
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It only does a 2 second prime when you turn the key off, just like key on.Was a mechanic for many years(many years ago) and have never seen this before.
If it runs for such a short time it is pressuriseing the fuel manifold because the regulator is not holdin sufficient pressure or needs adjusting or the pressure sensor is not working as it should . IF it is set to 75 psi and the pressure at turn off was 60 psi it will continue to run the pump until 75 psi is attained.. I would be looking in that area for the answer.
The pressure relief valve will hold for hours.It is only when you hit the key that the pressure drops to 45psi.I guess it could be a overly sensitive valve but thats a big job for a guess
When you turn the key the pump should start immediately to bring the pressure up to standard As it falls to 45 psi ( injectors are now opening) on turning the key it points back to a pressure sensor problem . They are normall located in the fuel manifold or line to the manifold and should screw in
Bill, I beleive mine is under the plenum so its a fairly long job.when the pressure drops it is immediate, maybe half a rotation, not enough pulses it would seem to drain the pressure 15+ psi. I guess my question would be is it possible at the first sense of vacuum could a bad relief valve open and release the pressure?
Also for ben, have you ever seen a GM pump prime when you turn the key off? maybe related maybe not
There may be a connection there as the regulator may be too sensetive or not adjusted correctly
I have seen bad TPS sensors be the cause of a no or difficult no start when cold.
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