[Solved] 98 3.0L Ranger - Troubleshooting starting, wire diagrams don't match

[arod529]

I'm troubleshooting an intermittent starting issue on a 98 Ranger 3.0L. Mostly not starting, with it sometimes starting for no explicable reason. I believe the issue is possibly with the PCM, or there is some wiring issue in between the PCM and fuel pump relay. I've found that fuel pump relay activation circuit is not getting power with key on at the under hood fuse box. Does anyone have the wiring diagram for the PCM and Fuel pump relay? I have the1993-20111haynes, but it only has 93 wiring and the PCM is not the same. Also, is there any easy way to test the pins on the PCM, there isn't anywhere to meter the pins from. Thanks.

NVM, I can't seem to delete this thread, so everyone can get a laugh at my stupidity. I was reading my fuse diagram wrong and testing the wrong relay, the PCM relay was bad. still wouldn't mind a correct wiring diagram though if anyone has that.

 

[Curious Hound]

Your 98 definitely has a different wiring diagram than the 93. Around 96, the whole system changed to the newer OBD2 architecture. I don't have the newer drawings for a Ranger. However. There are some tests you can do. First, you meed to realize that when you turn the key on to start the engine, the fuel pump only gets power for a few seconds to bump the pressure back up in case it leaked down. Then the pump is de-energized until the engine is running and needs constant fuel. Try spraying starting fluid into the intake while starting the engine. If it sputters and tries to start with the starting fluid, then you know you have spark and we can continue troubleshooting fuel delivery. One thing you can do is to measure your fuel pressure. Another thing to try is to bypass the fuel pump relay with a jumper wire. As long as you have decent fuel level in the tank to keep the pump cool, you can do this for 30 seconds to a minute to see if the engine will start that way and to measure fuel pump pressure. Another thing would be to try a different relay. Any 5 pin relay that fits the socket should work. I believe the air conditioning WOT relay is nearby. Just swap that one in and see if it makes a difference.

 

[arod529]

It's kinda weird, it has way less pins, I figure it would have been the other way around. I swapped the blower motor relay in. It would be nice if the the stock ford relay was marked with amperage rating, cant seem to find that info anywhere, but a 40 amp replacement should be fine.

 

[Curious Hound]

It's kinda weird, it has way less pins, I figure it would have been the other way around. I swapped the blower motor relay in. It would be nice if the the stock ford relay was marked with amperage rating, cant seem to find that info anywhere, but a 40 amp replacement should be fine.

Just use a relay rated equal to or greater than the fuse that serves the circuit. If 25 amp fuse for fuel pump, use a 30amp relay.