turns over but no start. I have been circling the web trying to find fix. customer parked truck in garage. went to start it a week later and no go. repaired a badly corroded wire under fuse panel. no go. checked pcm voltages, have proper voltages for 6v, 8v, 12v at pin locations where needed. have changed fuel pump. fuel pressures good. checked fuel pump relay (replaced), check ASD relay(replaced). same idea as other posters, where I have 12v going to coil but only for a second or two. then cuts out. I assume something to do with ASD. also found on web that it could be torque convertor solenoid. unplugged all harnesses going to transmission. no soap. still no fire. when you turn on ignition, I hear certain relays and solenoids clicking like normal, but still no fire. any other ideas??

 

Do you have an analog meter or a service scope to monitor the crank position sensor?

If it doesn't output pulses, the ECU won't turn on the ASD to run the pump and coil.

RwP

 

no analog meter or scope
I have been speculating about the crank sensor, but its a lot of work to change. was making sure I didn't miss a simpler check somewhere else

 

Simpler check is to use an analog meter to watch for the pulses.

HOWEVER.

The factory service manual has a simple "It's fried" test - not being fried does not mean it works, but if it's fried, it's dead.

The attached PDF is from the 1993 FSM; but it's the same procedure. I also included the FSM pages on replacing.

Also, as soon as you can, PICK UP A COPY OF THE FACTORY SERVICE MANUAL. It would be cheaper than what you've spent so far. Paper used off eBay, new disc from Bishko Books or a dealer (one such is Summit), or new paper from Bishko. (Note: New paper is 'spensive ... cost you about what that fuel pump did. Disc is under $40. Used paper ... well, it varies.)

One more thing - you say fuel pressure is good? Fuel pump relay coil is in parallel with the ASD coil; you should have 12V at the ignition coil if the pump is running. If not, it's probably the ASD relay and/or the wiring at the power distribution center.

RwP

 

well... I have 12v at coil but only for a second or 2 and then nothing. It seems like the ASD cuts it out. I have changed the ASD relay, but that didn't help either

 

That would be normal if the ECU doesn't see pulses; however, the fuel pump would run the same length of time.

Are you measuring while cranking, or while it's sitting there? Because you won't have power to the coil, injectors, alternator, fuel pump et al while it's just sitting there, even with ignition on, unless it sees the crank pulses.

RwP

 

I was measuring while cranking. I will check to make sure I have the proper voltages and ground signals at crank & cam sensors next. also check resistance at crank sensor

 

A quick no-cost sanity check would be to swap the fuel pump and ASD relays; if the relay is bad, it still won't run, but at least you'll have voltage there at the ignition coil.

RwP

 

I have put a new pump in and also changed the relays for pump and ASD relay

 

I'd still swap to see if it changed any; do consider that if stuff wasn't occasionally defective, we'd not have to have warranties.

RwP