FIXED: 93 ATX Cranks Fine, But No Power To Fuel Pump

[GT94SHO]

My 93 ATX quit Friday while I was driving and wouldn't restart (cranked fine). Verified inertia switch in trunk not tripped (open) - cranked, but still no run, so towed home. No CEL; No Codes, but noticed that with KO, I did not hear the fuel pump come on to charge the fuel injection system...so here's what I've done since then, in this order:

1. Re-verified inertia switch in trunk not tripped open
2. Re-tried KO; still no fuel pump prime; no fuel pressure at schrader valve on injector rail
3. Checked all fuses under hood and under dash
4. Installed new fuel pump; still same symptom (old fuel pump ran when bench tested!)
5. Grounded Fuel Pump test point on EEC-IV connector; still same symptom with KO; also checked for power to inertia switch w/DVM - read "0" volts
6. Replaced "J" CCRM with new "J" CCRM; still same symptom even with Fuel Pump test point of EEC-IV connector grounded
7. Checked ground on strut tower from negative battery terminal - OK

Other items of note...

• Up until 2 weeks ago, car had been sitting idle for 4 months (Sta-Bil added & on battery tender); when removed from storage, started and has run fine for past 2 weeks
• When re-connecting negative battery cable, get a pretty good arc- seems unusual to me

I'm stumped and not sure what to try next. Thoughts, ideas suggestions welcomed!

 

[rubydist]

so you will need to trace the power from the ccrm output back to the pump - somewhere there is apparently an open. the other possibility is that the signal wire from the pcm to the ccrm has an open, in which case the ccrm would never be commanded to power the pump.

 

[GT94SHO]

so you will need to trace the power from the ccrm output back to the pump - somewhere there is apparently an open. the other possibility is that the signal wire from the pcm to the ccrm has an open, in which case the ccrm would never be commanded to power the pump.

I've got PCM & CCRM unplugged at present. Where would I find wiring diagram/ID info so I can ID the fuel pump signal wires(s) from PCM to CCRM and CCRM to fuel pump, so that I can check continuity?

 

[Off Road SHO]

Assuming that the little 10 amp fuse in the corner of the under hood fuse box was checked and is still good like stated in #3 above (note: this little fuse supplies current to many devices, one of which is the coolant overflow bottle level sensor. That sensor gets clogged up with coolant scum and shorts out and burns up that little ten amp fuse easily) . With key in run position, make sure +12 volts is getting to pin 13 of the CCRM. This 12 volts is what trips the main relay inside the CCRM that powers up the PCM. The PCM can't do any of its jobs without 12 volts on pin 13 when the key is in start or run position.

Once you've determine that the above is good, turn the key off and attach your voltmeter to pin 5 of the CCRM and turn the key to ON but do not start. The volt meter should show 12 volts at pin 5 for no more than 2 seconds. If it does this...

Go to trunk and check for the 2 seconds of 12 volts on first one side of the inertia cutoff switch and then the other. You will have to cycle the key completely to OFF inorder for the computer to send another two second pulse of 12 volts down the line. If you get the 12 volts on one side but not the other, the inertia switch is either tripped or bad. You can test the inertia switch with the key off, your volt ohm meter set to ohms and with the VOM leads on each side of the switch, a sharp thump on the brace that the switch is fastened to will trip the switch open. If you have 2 seconds of +12 volts on both sides of your inertia switch when you cycle the key to ON, the fuel pump or the pump wiring is likely the culprit.

Tom

 

[rubydist]

Here are the ccrm wiring from the 1994 manual:

atx:

mtx:

 

[GT94SHO]

The 10A miniature fuse for Accessories under hood was blown. Many thanks for the post, suggestions and wiring information! I will update my progress...

 

[Off Road SHO]

Yesss!!!

 

[GT94SHO]

Yesss!!!

The coolant level sensor was bad, like Off Road SHO said, causing the 10A Accessory fuse to blow. Unplugged sensor & re-fused. Fuse held, engine started successfully!
Really appreciate the input from Off Road SHO and rubydist; you guys know your SHOs!

 

[Off Road SHO]

Rubydist is smarter but I'm more "experienced".

 

[rubydist]

LOL I'm pretty 'experienced' too, lots of mistakes along the way...

 

[GT94SHO]

Still going strong at 167k.

 

[sperold]

I know there is a high bar for a sticky, but this got solved so quickly and accurately, that it would be good to have it as a reference.