Ok this is what I know ,key on fuel pump to 45 psi but no check engine light ,try to crank and no spark ,checked no power to the coil packs ,checked as relay and has no ground from ecm, tach also has no response to cranking at all ,this truck started and ran fine then became hard to start but once started was fine ,then we went to if I left the key on for a few minutes it would start but now nothing , any clues would be nice ,is the crankshaft position sensor what controls all of this ?

 

ASD relay will only provide power to the coils for three seconds at Key on, and after that, only if it sees the engine turning. (crank or cam sensor) So, does the PCM initially power the coil packs, and then after the 'prime' never comes back on?

 

I don't believe it ever gets power to the coils but I will have help tomorrow to be able to check that ,but every reading to the as relay but the ground from the ecm ,it never trys to engage ,nothing in the pin from the ecm even at first and I checked the wire it's good ,I have not tried jumping the relay to see if it starts but I do get power to the coil packs if I jump it ,should I jump and see if it starts ?

 

If the fuel pump primes, I suspect the PCM is indeed actually doing it's job.... Have you checked the wire from the ASD relay to the coils?

Could also be a failed driver in the PCM for the ASD relay, but, that should set a code....... (asd control circuit failure)

 

Yes the wire is good and if I supply power to the 30 terminal on the as relay I get power to the wire at the coils and the wire to the as relay from the ecm is also good but I get nothing from it ,but that is checking by myself tomorrow I will have someone to turn the key on while I'm checking the voltage , but the fact the check engine light never test and the tach does nothing while it's being cranked seems maybe the ecm doesn't know the engine is turning over. So I will check more tomorrow and post what I learn.

 

PCM controls the ground side of the circuit for the ASD relay. I think power comes from the ignition switch.....

When you first turn the key on, the CEL should test..... If it doesn't, turn the ignition off, press and hold the trip reset button, and turn the ignition on. That will initiate a cluster test, it will turn on all the lights, and the gauges will go thru a full sweep. That will let you know if the bulb for the CEL still works......

 

My tach never moves when starting the vehicle. Never knew it should

 

Heyyou I have checked and no power at all to the coils when you turn the key on ,I just noticed what you said about resetting the system to see if the cell comes on and I will later ,also checked and found power 5 volts at the crankshaft position sensor and the camshaft position sensor and both lose and gain power as I turn the crank from .3 to 5 volts ,so I'm thinking the ecm is probably the problem any thoughts or to check .

 

Ok, if you aren't seeing power at the coils, ever.... do you get power to the injectors at all? (again, they will only see power for about 3 seconds when you turn the key on, after that, PCM needs to see the engine cranking. Check both conditions.)

 

I have a similar problem also 97 8.0, This truck has sat for about 9 years, low mileage. Did you solve your problem?