Next problem 04 Expedition, random die while driving

[AWAR]

The fuel pump relay on the 03-06 Expedition and Navigator is not serviceable. It is one of four soldered in mini relays inside the Body Control Module in the right kick panel. 97-02 and 07+ have replaceable fuel pump relays. The 07 and up have a different fuel pump/ fuse panel issue that Ford has a kit to upgrade the fuse panel.

When it dies to just runs out of fuel, the pcm thinks it is still running. The cruise will pull the pedal to try to maintain speed and the transmission downshifts as the car slows. The transmission keeps the engine turning until just about stopped and the tach drops to zero and the low oil pressure light comes on. All the gages stay up, a/c blows and the radio stays on. No check engine light or codes. After it sits for a couple minutes it will fire up and run fine. If I try to start it to soon it will flair a little on the fuel in the rail and then just crank like no fuel. It quit twice today so today was the day. I do have a new OEM pump assembly coming but it will not be here until next and the tank is full.

I pulled the schematics and came up with a plan to add an external relay and connecting it just like Ford does. Here are the schematics, 27-1 and 27-7. Continued in the next post.

 

[AWAR]

I first looked up the fuel pump in the powertrain control section, that gave me the second drawing. I had to back up to the first drawing to find the two power sources. The upper left of the second drawing shows the fuel pump relay and how it operates. The drawing sends you back to 24-1 to see where the source is and what controls them. 24-1 shows that the pcm power relay provides power to energize the fuel pump relay. That is labeled P on both drawings. The power to run the fuel pump is battery hot through fuse 9 in the BCM. 24-1 shows the hot all the time buss bar and comes down through the Y on both drawings.

Now we are on 24-7, the PCM controls the relay by grounding the circuit. The inertia fuel shutoff switch is powered when the relay is closed by the PCM. Then on to the pump. Another wire reports back to the PCM when the relay is closed and sending power to the pump.

The drawings show wire position, colors and connector numbers on the external plugs on the BCM. Power to close the new fuel pump relay comes out of connector 270a in drawing 24-1. I tapped into circuit labeled J at location 10 on the connector. It is a red 16 gage wire and it is fused by fuse 34 at 15 amps. The factory did not fuse the signal circuit to the OEM relay.

Connector 270b position 12 has the control wire that runs to the PCM, it is a light blue wire with a orange tracer. It is a 20 gage wire since there is very little load on the control circuit. 270b also has the tattle tail wire back to the PCM that reports when the relay is closed and passing power. It is on position 11 and is dark green with a yellow tracer and is 18 gage.

The power out to the pump comes out connector 270k on position 3, it is dark green with a yellow tracer. This wire carries the fuel pump load and it is a 14 gage wire.

Now I have accessed all the circuits except the battery hot circuit to fuse 9 which they fuse at 15 amps. They use mini fuses which gets them into trouble with the later trucks. Since fuse 9 only powers the fuel pump I used the fuse socket to tap power. I added an inline 15 amp fuse to power the load on my new external relay.

Here are a few pictures of the completed project. The green wire end shown in the second picture is dead.

 

[whtbronco]

Thank you. Your posts show well documented, easy to follow symptom, troubleshooting and resolution.

 

[AWAR]

It ran perfect today I ran it about 40 miles. Another thought about how it would quit on the road and how it would act when trying to restart. There is a tattletail wire back to the PCM that reports that the relay is closed and passing power to the pump. I think when the relay fails the PCM shuts off the injectors. After coasting to a stop and trying to refire the engine, it flares like there is still residual pressure in the rail. Then it cranks like there is no fuel.

This was just a passing thought.

 

[Broncoholic]

Good write-up for anyone wanting a serviceable relay.

I was able to de-solder and replace my relay pretty quickly. Still working 10 years later.