1994 TOWNCAR PERPLEXING PROBLEM

[autonut]

Please Help Anyone! I am ready to scrap an otherwise nice auto if I can't find an answer. I have an intermittent that is driving me crazy. This has been going on for about three years now. No fun when you get stalled on the highway etc. Seems to happen more in hot weather. I have tried to narrow it down. What happens is that the fuel pump does not get any voltage. I have replaced the PCM POWER RELAY, Fuel Pump & Cutout relay, and the PCM Power Diode.
This did not cure the problem. I strongly suspect the unit behind it which is called the "Powertrain Control Module". When stalled, I have poured water over this unit and it then did start. Not sure if this was just a coincident or not. This item costs approx around $300.00 if you can find one, thus hate to replace it if that isn't the problem. At my wits end on what to do next. If anyone has an idea please let me know.
Thought I would be smart and bought a OBD1 code reader which would perhaps tell me the problem. What I found out here, is that the computer resets every time the key is turned off thus my new reader read NOTHING and a waste of money.
Lee

Can anyone explain to me the function of this unit? Why is it hooked to the fuel pump relay etc??
Lee

[Dan Szwarc]

A 22 year old car with an electronics problem.

Welcome to the world of electronics.

The problem could be anything from simple board contamination to capacitor failure to cracked solder joints. None are easily repairable.

If you can buy yourself a BUM PCM and open it yourself to see what's inside, you will learn a lot about them.

As an electrical engineer I can tell you that even the experts are perplexed when these fail. Unless you know the design, they can be impossible to fix.

[autonut]

Yes finding a problem in an electronic module where no schematic exists is next to impossible to repair. They are not meant to be, of course. So one has to work around that if really the problem. First of all, how does one determine if it is truly bad? But to make matters worse, when the problem only occurs perhaps once/month it makes it a thousand times worse. So what does one do?
One of the things that bothera me is that there is a computer in the auto. First of all, where can one find what the computer monitors? I can't even find that information! The Service Manual is completely blank regarding the fuel circuitry. There is no mention of it, why?
Another thing about this computer is that I was told that it resets when you shut the key off. Why in heavens name would a car mfg want to do that? I thought almost all autos kept the codes stored in the computer? Did I get right information? Thus I am wondering if anyone has changed the circuit so that this computer module is connected live all the time so that codes are not lost?? I would like to do this to aid in finding my problem. I need some method of madness to track down my problem. Hope someone has had some experience with this '94 computer module and could aid me to rewire the circuit to maintain its engine trouble codes. Of course I don't even know if the computer has any error codes regarding the fuel system relays etc.
Lee

[JimA]

Why wouldn't you bypass the computer controlled power to the fuel pump? I.e., add a circuit with relay, low oil pressure switch, inertia switch, and alternate feed from the starter solenoid.

[mlj427]

On my 1992 Ford F150 with a 5.0 would hold the codes for a period of starts. I think it was 10 in the history. Could you leave it hooked up and drive with it until it stops and see if there is a code?
Mike

[autonut]

The latest. Still trying to pin down my problem. Thus I purchased a ABD1 Engine Ford Code Reader #3145 thinking I could read the computer which might lead me to the intermittent problem. But dismay in the fact that the code reader will read nothing! It won't even acknowledge that it is hooked up to the computer which it is suppose to do according to the manual. Does anyone have one of these code readers? Anyway it should work but why won't it? It is brand new and not defective. Still searching for clues of why it will not work as I am really now confused. It did read in the manual that there were a few (only a few) cars in 1994 & 1995 that Ford introduced the EEC-V or OBDII and it was used in a very limited number of '94s & '95s. I am wondering if I could have an auto with an OBDII computer system. The book states that this tester is only compatible with the EEC-IV or OBDIV computer system. Question is -- how can I determine whether mine should happen by chance to have this EEC-V computer rather than a normal EC-IV? Would be my kind of luck. Can anyone help me? I am really lost!!!
Lee

[autonut]

Correction to my previous statement about the computer holding the codes.
Just to state that the mechanic who told me that my Lincoln would only hold the codes while the key was in the "ON" position. He told me that once you turned the key off all codes would be lost. He was full of crap because another mechanic from another shop told me this was not so. I didn't think it sounded reasonable. I looked up the wiring diagram and the power is always fed power on pin 1 directly from a hot at all times fuse. There is a switch power going to the computer on pin 57 but not sure what that does. Can anyone give me any more info on this computer? Nothing written about it in either the Electrical Manual or the Service Manual.
Lee