98 Ranger w/ 96 Exp. 5.0 having fuel issue

[Rangstang]

I swapped a 96 Explorer V8 into my 98 Ranger. Created a number of issues due to the amount of changes in electrical circuits. The PCM had a few wires non-existent on the Explorer that were present on the Ranger and vise-versa as well as some color code changes, but the AC was the worst...

Here's my issue. I have +12V at the fuel relay's coil and common pin, but I'm not getting the ground signal issued by the PCM to energize the relay. The PCM did function 4 weeks ago when I pulled the motor. I hotwired the fuel pump and was able to fire the truck up.

Anybody know what signal(s) is/are needed for the PCM to drive the fuel pump relay?

 

[bobbywalter]

pcm sees power. and strobes the pump.


if i remember right it simply sees power to strobe the pin 80 ground, and idm/pip/saw loop to keep it running.

pin 40 is the monitor iirc...its powered under command and dark green

pin 80 is the ground signal from the pcm to the fuel pump relay. light blue and orange....but...you have to look carefully because the constant power feed is the same color sometimes. i have seen them switched and blow the board before. and have done it myself in external work.

if the computer is not grounding the negative relay pin and the wiring is correct, and manually running the pump allows the engine to run there is likely some minor processor damage.

 

[Rangstang]

pcm sees power. and strobes the pump.


if i remember right it simply sees power to strobe the pin 80 ground, and idm/pip/saw loop to keep it running.

pin 40 is the monitor iirc...its powered under command and dark green

pin 80 is the ground signal from the pcm to the fuel pump relay. light blue and orange....but...you have to look carefully because the constant power feed is the same color sometimes. i have seen them switched and blow the board before. and have done it myself in external work.

if the computer is not grounding the negative relay pin and the wiring is correct, and manually running the pump allows the engine to run there is likely some minor processor damage.

Thanks for the response Bobby.

You are correct about pin 80 being the pump relay GND source and the color is light blue/orange. I didn't see another LB/ORG wire, but I'll double check. As for the monitor pin 40, if that were miswired, the PCM might not send the signal on pin 80, correct?

 

[Rangstang]

I stand corrected.

There are two LB/ORG wires. One to pin 80 of the PCM and the other to accessory power. Good work Bobby! I'm pretty sure you solved my problem. Thanks!

Update: Corrected problem and the fuel pump fired right up. Luckily, the PCM survived. Thanks again!