2003 Ford Expedition Fuel Pump Relay (R303) Damaged

[whtbronco]

I have not run an external relay on mine. I will if it fails again, I believe 87a is not needed, it only needs to be 4 wires. Power in, power out, ground and switched power in.

 

[CertusExpo]

I have not run an external relay on mine. I will if it fails again, I believe 87a is not needed, it only needs to be 4 wires. Power in, power out, ground and switched power in.

I ran into THESE instructions in another Post by @DavidJodoin so I’m left wondering which is correct?

 

[whtbronco]

I have wired up many solenoids in the past for lights, winches etc... In every case I used 4 wires. I'm sure you can use all 5, I just haven't had a need. The factory relay has 5 pins, but best I can tell from the electrical diagrams only 4 are used.

I didn't remember what 87a was for so I went and found a diagram.

87a is for power output on a circuit that is normally closed(on).
87 is for power output on a circuit that is normally open(off). battery power out to fuel pump
30 is for constant power in(from the battery). battery power in
85 is for the ground.
86 is for the switched low current power in. think of this as from the ignition switch

Not sure what we'd use 87a in this case for since it's backwards from how the fuel pump is wired. 87a would complete the circuit when the ignition is off and open it when the ignition is on, no power to the pump when the ignition is on. 87 supports power out from the relay when the switched power input has power. The fuel pump circuit is open when the ignition is turned off and the circuit is closed when the ignition is turned on so power goes through the relay to the fuel pump.

I can't see the obfuscated link in the above post so I won't try to select it.

Someone please correct me if I'm wrong.

 

[CertusExpo]

I have wired up many solenoids in the past for lights, winches etc... In every case I used 4 wires. I'm sure you can use all 5, I just haven't had a need. The factory relay has 5 pins, but best I can tell from the electrical diagrams only 4 are used.

I didn't remember what 87a was for so I went and found a diagram.

87a is for power output on a circuit that is normally closed(on).
87 is for power output on a circuit that is normally open(off). battery power out to fuel pump
30 is for constant power in(from the battery). battery power in
85 is for the ground.
86 is for the switched low current power in. think of this as from the ignition switch

Not sure what we'd use 87a in this case for since it's backwards from how the fuel pump is wired. 87a would complete the circuit when the ignition is off and open it when the ignition is on, no power to the pump when the ignition is on. 87 supports power out from the relay when the switched power input has power. The fuel pump circuit is open when the ignition is turned off and the circuit is closed when the ignition is turned on so power goes through the relay to the fuel pump.

I can't see the obfuscated link in the above post so I won't try to select it.

Someone please correct me if I'm wrong.

Here is a Copy/Paste of the other instructions I located:


“
So I know there is a bunch of people that like to replace the CJB (Fuse Panel). But remember that all you are doing is resetting back to the same potential problem being able to happen again. The circuit board was not designed properly to take the heat from those undersized relays. If the PCM relay is good, and you only fried the fuel pump relay, I recommend just putting an external relay on and wiring it in. There are videos to do this, but a lot of them suggest wiring it in improperly so that the fuel pump runs whenever the ignition switch is on. I have an 05 Expy and this is the proper way to wire in an external relay....

First... buy one of these external relay kits... its rated for 30 amps.
https://www.amazon.com/gp/product/B074QV54V1/

And one of these (mini fuse tap) ...
https://www.amazon.com/dp/B01LFXA5UA/

And you will need some inline power taps...
https://www.amazon.com/dp/B07WFPFY1C/



Then wire it in as follows...

Your relay has 5 wires. You don't need the center one. So all you need are the 30, 85, 86, and 87 terminals that correspond to the relay harness. 30 is power always on, 85 is a ground that activates the relay (it completes the pin 86 circuit), 86 is powered when ignition is on (engine running or not), 87 is power out only when the relay is engaged (this will go to the fuel pump)

The reason most videos are wrong is that they wire the ground to a normal ground. This means that the minute you turn on the car the fuel pump runs constantly. How its supposed to work is that the PCM has a ground going to the fuel pump relay that is only on 1.) when you first turn the ignition to the on position and its only grounded for the 2 seconds of priming then disconnects and 2.) When your car starts and it then needs constant power to the FPDM (Fuel pump driver module)

So what you want to do is to replicate that circuit that includes the ground from the PCM. Here is a way to do it that works the way it should...

First you need power to the new relay... fuse 9 (15) amps will work because its KOEO (Key on Engine Off).
Wire that Using a fuse tap to get power for the pump, fuse 9 (15A), wire that to 30 on your relay. Use a 20 amp fuse for the second fuse (put the 15 amp fuse on the lower socket the 20 amp on the upper socket. Basically you just made a new circuit.

On the C270A plug there is a red/yellow wire... that is Key on Engine off or on power. Basically power that only goes on when the ignition circuit is active. Use an inline tap to wire that to the wire that corresponds to 86 on your relay.

On C270B, there is a thinner guage black wire in the corner of the plug. This is ground from the PCM. On some years I believe its LT BLUE/Orange, but for 2005 its black. You can cut it or do an inline splice... I always opt for the inline splice for grounds. It is pin 12 of c270B and wire the harness side of it to 85 of your relay using an inline splice.

Now the relay should work, and you can test it before doing the final connection by turning the ignition on and you should hear a click from the relay. If this woks, you now just need to feed power to the FPDM.

The dark green/yellow wire of C270B feeds power to the FPDM... cut that and wire it to terminal 87 of your new relay.

Your car now has a better, and replaceable external fuel pump relay. Doing it this way will not fry your CJB and is easily replaceable if it were ever to fail again.

As an Amazon Associate we earn from qualifying purchases”

What do you think @whtbronco

 

[whtbronco]

Sounds like what I said, 4 wires. That description is better than mine though.

 

[CertusExpo]

Okay, this took longer than I thought because I changed my plan and redid the PCB connections. I didn't feel that butt soldering the wires directly to the board would hold up.


So I researched then ordered and changed things. This was what I ended up doing.

I'll be doing a full tech write-up, with lots of pictures.

 

[whtbronco]

Well it certainly looks nice.

 

[CertusExpo]

Here is the finished (spare OEM) fuse box ready to be installed once I get my quick connectors tomorrow.



I realized that the second set of 'repair instructions' give the step by step to BYPASS the built-in fuel pump relay circuit by tapping into the appropriate and specific color coded loom wire for the needed purpose as follows.
Relay 85/Black to Blue/Orange @ C270B (or Pin 12)
Relay 86/White to red/yellow @ C270A
Relay 87/Blue to Dark Green/Yellow @ C270K

So I'm setting that up as well for a redundant 'fix' if there were ever a failure of a relay connection at the PCB. I could switch the connections out and be back on the road in minutes. Which is why I'm using quick disconnect connectors. (That second lone red wire is the fuse tap coming from #9) Which would connect to Red/30 on the relay.



I removed the damaged (second) fuse box that's currently installed on the truck. The last time Bonnie ran, R203 (PCM Relay) was getting too hot to even touch and was melting beyond use within 10 minutes. I disassembled that fuse box and WOW, the contacts for R203 are FRIED!
I'm not even sure I can use this other PCB.