RPetty_43

1993 Ford F150 5.0L. Have tried everything and all tests are good. The only odd thing is that the low current side of the fuel pump relay shows 5.0V with KOEO condition. I believe this should be 12V. However, the fuel rail has 45psi when cranking over..... 150-160 compression, strong spark, PIP passes all tests, and even if I dump fuel into the plenum, not even a flicker of life. I've never seen anything like this. And it ran fine, then died. New PCM, atc., etc.... It's like it is possessed. Any help would be most appreciated.

RLXXI

Try a known good ignition coil, I know you said it had good spark but there was a few instances on 3 different trucks at the dealer I worked at that all had good spark and wouldn't run, we replaced the coil on all 3 and all 3 came back to life, to this day I still don't know what the deal was.
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RPetty_43

Forgot to list all the new components:

PCM (3)
TPS
Coil
ICU tests OK
PIP tests OK
Relays
MAP
Plugs
Wires
Cap
Rotor
Timing is spot on at 10 degrees before TDC
Kitchen sink

I have worked on 100 year old engines and if you have compression, fuel, and spark you should at least get a pulse.

The only odd issues so far are as follows:

1. With KOEO, injectors have 12V on both sides.
2. With KOEO Fuel Pump relay has 12V on high current side, 5V on low current side. But the fuel pump test shows 45psi at the rail.
3. It runs when it feels like it and has, then stumbles and fails and starts again weeks or months later only to fail again in the middle of a busy intersection

Today I will spend some time looking for a short under the oddly designed intake plenum. What were they thinking? NOT!

gDMJoe

For your consideration .....

HINT/TIP: You'll find posting in thesection more helpful/appropriate than General F150 Discussion posts.
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RLXXI

The injectors should only have 12v on the power side, the other side is a pulse width modulated ground from the pcm need a noid light to test but sounds to me like you have an open ground somewhere.

I'd be looking at the distributor real hard. Make sure it hasn't sheered the gear roll pin.
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RPetty_43

First thing I thought of as I had that happen to a Ranchero long ago. But this doesn't drift. It stays at 10 degrees, spout off, and the vehicle has run for periods of time. Where would the open ground be is the problem as the ICU PIP test shows a nicely spaced pulse. I may also try the pulse test directly at the injector. I will double check the distributor as well.

RPetty_43

I tried a pulse test on the truck and the injectors pulse just fine when cranking. So I guess the 12V on both sides is only during the KOEO state.