Help - X starting problems PCM?

[pmcmaster]

I need some real help on this starting problem:
Explorer 97 4.0 sohc

Problem started about 6 weeks ago, at first it only happened bout once a week, now its happening all the time.

Go's like this.
Start X, do journey (no problems drives fine)
If I Stop X, leave for few minutes, re-starts fine.
But if I Stop X and leave for say 1 hour when I try to restart, the engine turns over ok but refuses to fire up. Try again after say another hour it sometimes starts sometimes won't start. If if dos'nt start try again next day sometimes it starts sometimes it dos'nt and so on and so on!!!!!!!!. I spent 2 days last week trying to start it with no luck, came back to it a week later - started first time, drove about 40 miles (no problems) turned it off and tried to start it again NOTHING!!!!!.

The actual reason it wont start is: No fuel at the Injection test valve. The reason for no fuel is the fuel pump relay switch (switch side) is not being grounded. I have checked fuses, the cut off switch and the relay switch itself. When it does start the engine management warning light is NOT showing any errors but does the error log always switch the warning light on?

Any ideas? - could the PCM be faulty? - could there be a problem with the CPS. I'm reluctant to take it to the Ford dealers as overhere in the UK the last one charged me £60 ($100 ?) just to plug in his bloody computer. Most of the private guys dont have the American type connector (European connectors have 16 pins)

Help me before I go CRAZY.......

 

[BillWms01]

Pat, my '97 with the 4.0L OHV acted similiarly. I changed both the relays (fuel pump and I think PCM), with no postive result. Then I changed the Crank Position Sensor, and have had no starting problems since. If CPS is only sending signal to computer intermittently, computer doesn't know when engine is turning and needs fuel.

 

[pmcmaster]

Thanks Bill,
The CPS is where my suspicions lay, trouble is, in the UK the cost of spares are a killer and I was hoping for your sort of confirmation before a bought a new one. Example I just got a quote for a new tail light module - £98 or about $185 in your money.
Pat McMaster.

 

[BillWms01]

I think my replacement CPS was around US$40. I'm sure there's some way to test the existing unit, but I don't have a service manual. I'm not sure whether you'd check ohms or volts, etc. but some sort of electrical signal varies according to the crank position. If you knew what it was, you could hook a meter to it and see if it changed while being cranked over.

However, I agree there's some problems you don't want to attack by trial and error. For those, when I can see it's over my head, I usually take it to a mechanic. Of course, about half the time I do, he's not much better off than I am.

 

[pmcmaster]

I have been told that its about £60 ($100) over here. I've got a Haynes manual which gives a test for the CPS although the manual states it should kick out 1.5v AC but some of the threads I've followed on similar problems talk about 10v so not sure on this. Following these these threads I've discovered a useful site that gives details on how to get the EEC error log codes without needing an electronic reader (www.fordfuelinjection.com) so I've bought a new multimeter (with AC range) and will try testing the CPS and getting the error codes out as well. That is if it ever stops raining over here, yesterday was the coldest July day on record!!