my 92 wont start

[obenauf]

hello everyone i have a 92 xlt that wont start i have done alot of searching and i still havent found the answer heres the sinario it will fire on ether the fuel pump doesnt cycle when you turn the key on. but when you jumper it at the self test port it runs i got codes 542 and 543 when i did a code check now i am stuck as where to go from here any help would be greatly appriciated thank you

 

[marragtop]

Are you saying that if you jumper the self test port, the fuel pump will prime? If so, check the PCM and fuel pump relays.

 

[obenauf]

no i am saying that when i jumper the fuel pump lead in the self test plug the fuel pump will run which i think indicates that the fuel pump relay is good is this correct?

 

[MrShorty]

That would be my interpretation. So it would appear that the computer isn't telling the relay to close. Is there a break in that wire between the fuel pump relay and the PCM? good grounds at the PCM? Will it start and run when you jumper the fuel pump test connection?

 

[obenauf]

thanks for the reply mr shorty i did a continuity test from the computer to the relay and the wire is good and there is good ground at the pcm it will not start and run when i jumper the fuel pump at the test connector does this indicate that the computer is bad? or is there something that i am missing? thank you for the help

 

[lifeguard379]

check all fuses?

 

[MrShorty]

thanks for the reply mr shorty i did a continuity test from the computer to the relay and the wire is good and there is good ground at the pcm it will not start and run when i jumper the fuel pump at the test connector does this indicate that the computer is bad? or is there something that i am missing? thank you for the help

For now, I'm going to assume the pump generates adequate pressure, though I would suggest you take a few minutes and put a fuel pressure gauge on it to verify.

I hope I can organize my thoughts in a way that will make sense.

Where it runs on ether, that suggests something is wrong with the fuel system.
Fuel pump will run (and, presumably, generate adequate pressure) if the circuit is completed, so the problem (or part of the problem) is that the computer is unable to close the relay. If everything else were working correctly, the engine should run on its own by manually closing the relay. Problem appears to be deeper -- extending to the computer's ability to fire the injectors.
Engine can run on ether without the PCM, because the ICM can fire the spark plugs, as long as the ICM has power.

So, at this point, I'm wondering if the PCM is doing anything. Is the PCM getting power? Are the injectors getting power? Double check the PCM grounds: it's not uncommon for the "pigtail" that comes off of the negative battery cable for the PCM to corrode.

 

[lifeguard379]

check all EEC fusses. its the cheepest thing to check so i would do that first.

 

[obenauf]

i did a fuel pressure ckeck and it only has 10 psi but i did notice that there is no pressure immidiatly after disconnecting the pump so the line isnt holding any pressure is this a bad fuel pump or a fuel pressure regulator? the pcm is getting power and the ground seems to be there and i checked the injectors and they are recieving a pulse so this indicates the ecm is working but why is it not sending a signal to the fuel pump to turn on with the key and why isnt the fuel line holding pressure? thanks for the help

 

[MazdaGreg]

Didnt see this in the thread. Did you by chance check your Inertia switch?

 

[obenauf]

ok after some more searching i take it that the ckeck ball in the fuel pump is stuck that is why there is no pressure in the fuel line so i will need a new pump but iam still stuck at why the fuel pump will not run when the key is in the on position there is power to the pcm and the ground seems to be good i checked the wire from pin 22 to the fpr and it has continuity where do i go from here? thanks for the help

 

[MazdaGreg]

So you do NOT have 12 volts at the pump connector?

I would check the inertia switch first. if it seems ok, check for 12v before and after the switch.

Then, i'd move back to the FP Relay. Check before and after for power.

 

[fixxxer]

I am really confused about the codes you say were read, codes 542 and 543? For a FORD EEC-IV/ODB-1 or OBD-A system, all the DTC's should be a 2-digit codes.
http://www.extreme-check-engine-light-codes.com/Ford OBD1 Decoder.htm

 

[obenauf]

fixxer check out fordfuelinjection.com that site is very good and should get u the right info

 

[MrShorty]

ok after some more searching i take it that the ckeck ball in the fuel pump is stuck that is why there is no pressure in the fuel line so i will need a new pump but iam still stuck at why the fuel pump will not run when the key is in the on position there is power to the pcm and the ground seems to be good i checked the wire from pin 22 to the fpr and it has continuity where do i go from here? thanks for the help

With a voltmeter at pin 22 (common to ground), can you see the computer command the relay to close (voltmeter should switch from 12 V to 0 V back to 12 V)?

fixxxer, it's true that many EEC-IV applications output 2 digit codes. Starting in '92 for the 4.0, they started outputting 3 digit codes. 2 digit or 3 digit codes is determined by application, and the only way to really know which applications output 3 digit codes is to look it up in a manual that lists codes by year and application.

 

[obenauf]

thank you mr shorty your knowledge is very appriciated thanks again