95SWB

I tested all the relays today and they all tested good. I somewhere read that the o2 sensor and fuel injection harness was on fuse #22? I may be wrong, but a couple years ago I was having a similar issue and it ended up being chafed wires on the fuel injection harness. I removed the upper intake this afternoon and it is pretty dirty but the harness doesn't seem to be damaged. I was looking on the previous posted diagram and conclusion is that something in the diagram is shorting and blowing a fuse? It will crank easily and idles great can rev motor and doesn't die, but as soon as I close the hood and put it in gear I'm only able to drive about 50 yards and it begins to stumble and quickly die. Have done this 5 different times, same distance same fuse every single time.

95SWB

According to the diagram, I have a short in the wiring powering the ICM, Radio Capacitor, Ignition Coil, Distributor, PCM Diode, or PCM Relay. Are their any other circuits operated by maxi fuse #22 from the power distribution box?

sam29078

Wiggle the wires

95SWB

Spent all day wiggling wires! No luck, all the diagrams I'm finding are all varying. Have the fuel injection harness out and testing circuits nothing is crossing except injectors 1,3,5 and 2,4,6 which I assume are "2" banks of injectors and when the firing order is 1-5-3-6-2-4 does that mean when cyl1 needs fuel that cyl5 and cyl3 also receive fuel? Which means the computer is dumping fuel into cylinders when not need? I know that is off subject but this could be a huge part of why everyone complains about fuel mileage. Anyways I believe that the injector harness passes, would the rest of the engine harness that supplies distributor, knock sensor, coil, radio capacitor and a/c switch? From there if everything passes it will just be power distribution box pcm and ignition switch on column? I have replaced key switch computer icm map sensor coil and problem persist with new parts and old parts.

sam29078

Have you tried swapping the relays around?

95SWB

Yes with no change, also tested all relays all passed.

sam29078

Fuse box melted on bottom side? Pcm relay, coil, wires rubbing somewhere and ignition coil is what I see being bad.

95SWB

Never seen wires rubbing not melted underside of power distribution box would do the same with two different coils two different icm two different distributors and yesterday I cranked it up and drove it with no problems other than code 327 and I already knew my egr valve or dfpe sensor wasn't operating. But drove truck for 2 hours non stop and never blew fuseU and now I'm puzzled to why it was blowing fuse anyway.

RPetty_43

Cranks But Won't Start
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.


Forgot to list all the new components:

PCM's (3)
TPS
Coil
ICU tests OK
PIP tests OK
Relays
MAP
Plugs
Wires
Cap
Rotor
Timing is spot on at 10 degrees before TDC
Compression is 150-160 across the board
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!

Any help would be most appreciated.

Chris_1

iTrader: (1)

I think that the fuel pump is supposed to get 12v for the initial prime and then something like 5 or 6v for constant run if the engine is turning. The way I've been lead to understand it anyway. I think that's why there's 2 circuits in the relay.

I have seen a problem occur with the wiring under the relay corroding because of the constant power. You have to unclip the power distribution box, unclip the bottom cover and turn it over to look.
Just a possibility, but at this point you have to check everything I guess.
Other strange possibility is maybe a bad ground ?

Just throwing things out there.