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Chuck
Chuck, ASE Certified Technician
Category: Ford
Satisfied Customers: 2100
Experience:  33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
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1997 expedition cranks no start. fuel pump wont turn on. replaced

Resolved Question:

1997 expedition cranks no start. fuel pump wont turn on. replaced it and noticed only 6volts at the pump. replaced the fuel pump relay and bypassed the inertia switch. also showing only 6volts at the inertia switch. If I jumper 30 and 87 on the fuel pump relay I get 12v to the fuel pump but the engine will not start. Starting fluid in the intake and the engine starts. It seems the fuel pump relay is not engaging. I tested both relays, old and new, they both work. Old fuel pump works when plugged directly to the battery.

Signal flow has brought me through the following:
12v at fuse 19 - fuel pump
12v at fuel pump relay terminal 30
6v at fuel pump relay terminal 87. this 6v is coming from the PCM, the relay is not engaging.
10v at fuel pump relay terminal 85 - this is fed by the PCM
PCM circuit looks good also from Fuse to ground Replaced the PCM and same thing. Cranks but no start. What a freekin headache!
Submitted: 7 years ago.
Category: Ford
Expert:  Chuck replied 7 years ago.

HiCustomer

 

I read your previous post where you checked the fuel pump relay and had 12V on fuse 19 and on pin 30 but only had 6V on pin 87. What are you reading on the coil side of the relay on pin 86? Are you getting a good ground from the PCM on pin 85?

The coil side of the relay has to energize to create magnetic field to pull the switch side closed. I suspect that you are not getting enough juice here to do this. Also since when you jump pins 30 and 87 and get 12V to the pump and it still doesn't run confirms this. Pin 86 gets its power from the PCM relay and I suspect your problem is here and not at the fuel pump relay.

 

Here is the wiring schematic for this

 

graphic

 

Check power on pin 30 and 87 of the PCM relay see if you are not getting the same results there also. If so then jump pins 30 and 87 like you did on the fuel pump relay and see if it runs then. If it does then check the PCM diode I suspect that this is your problem.

 

Customer: replied 7 years ago.
Ok sorry for my delayed response, I had to go out of town for work only to come back to 3 straight days of rain... I live in FLorida.


So this is what I got:

PCM diode passes 12 volts in one direction

Fuel Pump relay pin 86 gets 12v when key is on

Jumped 30 and 87 on PCM relay and same thing, not engaging fuel pump relay

Power Distro Fuses 30 & 24 good

No continuity on pin 85 of the Fuel pump relay to ground, so I grounded it and the relay closed so this tells me that the PCM is not grounding the relay. I bought a used PCM online and i get the same result from both PCM's. Is there any way to tell if the pcm is turning on?

i opened up the wire harness to the PCM and checked continuity between all ground pins and ground, this is good

Engine fuse module fuse #1 (pcm) good and continuity to battery terminal and to the pcm pin 55 so this tells me that im getting power to the pcm

I appreciate your help so far!


Customer: replied 7 years ago.
I was also thinking, how do you guys test or reprogram a PCM? Does it need to be in the vehicle or can I bring the PCM unit to a Ford dealer and have them test it?
Expert:  Chuck replied 7 years ago.

Are you sure you are not battling a PATS problem? What is the anti-theft light doing when you turn the key to the run position?

 

No at the dealership we can only test the PCM on the vehicle.

Customer: replied 7 years ago.
The antitheft light is flashing, I'm not an expert but It is my understanding from reading the diagrams that the pats cuts the starter. Is this right? Will the pats cut voltage to the fuel pump via he PCM? Man if this is the problem I'm going to go slit my throat ;). !
Expert:  Chuck replied 7 years ago.

On this vehicle it does not have a starter interrupt it disables the fuel pump.

If the anti-theft light is flashing rapidly when the key is turned to on position this is your problem.

Sorry I didn't put you there sooner but you fooled me with the 6V at the inertia switch.When you said you jumped the PCM relay and the fuel pump relay still would not energize I was saying oh s%#*#.

 

When you turn the key to on position the theft light should come on solid for about 2 seconds then turn off.

 



Edited by Chuck on 3/13/2010 at 8:39 PM EST
Customer: replied 7 years ago.
Wow, I hope this it it! I'm going to trouble shoot the circuit. Is there a reset procedure or anything I should look for?
Expert:  Chuck replied 7 years ago.

Here is a copy of the wiring schematic if you need it.

 

graphic

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