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Ok. for all of these tests I need to make sure we're all speaking the same language:
The 4 positions of the ignition switch are lock, accessory, on, and start
When I say I put the key in the "on" position, I am in the "on" position as pictured above. When I'm doing these tests that is the position I am using.
I am not using the start position. PDQFORD: when you say "run" that is the same as "on"? I just want to make sure I'm doing everything properly.
Thanks to everyone for helping me trouble shoot this issue!
Yes, ON is the same as RUN. I think some year models have RUN, others have ON. Same thing, means the ignition is on. When ignition is on, then the PCM relay should be powered on coil side, follow the procedure from PDQFORD on this. As for fuel relay, memory escapes me on how this one will behave. I know it will prime the fuel pump when you turn on ignition, but I believe the fuel pump will stop and wait for engine to start before being energized again.
Now touch the positive lead of your volt meter to the socket where pin 86 of the PCM relay normally goes.
You should see battery voltage on your meter. (If not, verify that the 30A fuse #30 in the CJB (Central Junction Box) under the dash is good.)
Yes, ON is the same as RUN. I think some year models have RUN, others have ON. Same thing, means the ignition is on. When ignition is on, then the PCM relay should be powered on coil side, follow the procedure from PDQFORD on this. As for fuel relay, memory escapes me on how this one will behave. I know it will prime the fuel pump when you turn on ignition, but I believe the fuel pump will stop and wait for engine to start before being energized again.
Just for reference, the PCM controls the ground side of the fuel pump relay coil, We have the relay out of the circuit during this test so the PCM can not energize the coil side of the fuel pump relay nor can it pull the relay in. So for this test we should see steady battery voltage on fuel pump relay socket 86 when the ignition switch is in the "ON" (thank you @turbo39151) position, and should see steady battery voltage on socket 30 of the fuel pump relay "always".
Just throwing in my two cents here, but I’ve had an issue with my SD dying in the same way, went through all the electrical test as you did but came-up with nothing.
so I moved some of the wires on fuel pump modulator at the rear of the truck and lost power to pump, the wiring at the connection was powder inside but with the moisture in it was still conducting until I moved it and knocked it loose.
Went to the Ford store and got a new pig tail, soldered it back together and runs great.
Here's the wiring diagram for a '99 Expedition. Probably more or less identical for the '00 Expedition on this section.
If you do see 12V at the fuse, check the PCM power diode, it's located in the junction box under the hood.
Edit:
Here's a diagram which shows the PCM diode placement.
I was comparing the diagram with my junction box lid. It's a little different but close enough. I have not pulled the PCM diode. Not sure if there is a way to check it.
Just throwing in my two cents here, but I’ve had an issue with my SD dying in the same way, went through all the electrical test as you did but came-up with nothing.
so I moved some of the wires on fuel pump modulator at the rear of the truck and lost power to pump, the wiring at the connection was powder inside but with the moisture in it was still conducting until I moved it and knocked it loose.
Went to the Ford store and got a new pig tail, soldered it back together and runs great.
Do you have a pic of what I'd be looking for? I'm getting desperate. I need to get this thing back on the road.
Testing the diode is easy. Use resistance (ohms) and measure between the two pins on the diode. Then reverse the leads and measure again. The diode should give a low resistance in one instance and infinite (OL or similar) the other way.
But, if you have no battery voltage at fuse 30 in the junction box under dash then we need to find out why that is first. That's the one that feeds everything, without voltage on that fuse, then ignition system and PCM relay will never be energized, so this is the problem.
Under the dash, I got nothing. I checked only with the test light. Don't think the multi-meter would fare any different.
Just to be clear, you had your test light lead connected to a GOOD ground,
the ignition key was in the “ON” position,
and you probed both sockets of fuse #30 in the CJB under the dash,
and you found no power?
If no power, were gonna have to back track to the ignition switch to see if the ignition switch is sending power to this circuit.
Have you ever had a water leak from the windshield that may have dropped water on the back side of the CJB?
Can anyone post up a picture of the correct wiring diagram showing the ignition switch pin out to PCM relay circuit?
(I kinda think you are digging near the ‘taters now!)
Following is the diagrams which include the circuit from ignition switch to fuse 30 in the junction box under dash. From what I can tell, if there's no power to fuse 30, the instrument cluster and PATS would be affected as well. The instrument cluster does have more than one power source, so it may not be completely dead, but please confirm that there's no battery voltage on fuse 30 as I think that feeds most of the ignition system.
I'll have to go out and double check a few things. However, it's cold and rainy again. I'll see if I can catch a break in the weather and check...
Odd thing about this whole issue is that I've owned this truck since 2007 and have NEVER had any issue even remotely similar to this. No water leaks, no electrical issues nothing.
Yet, I have an engine swapped in and this issue appears? Just seems too weird.
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