289 Carbed swap wiring

Ranger289 · Oct 24, 2017

Hey guys,

I've hit a bit of a snag in the wiring on my '98 2wd 289 swap. When I pulled the 4.0L OHV out I cut the 42 pin connector (C124) on the engine harness because most of the wires there I don't need. Now naturally, being a Ford, half of the wires in the harness aren't the same colour as the manual says they are. So far I've got my HEI wired up and the oil pressure and coolant temp sensors plugged in. Now my issue is that I can't find the wire that the starter relay is supposed to power to go to the solenoid, nor can I get power to flow properly through the relay. Can anyone tell me if the relay is hot all the time with the ground being switched, or is it the conventional switched 12 volt? Also, I sold the PCM with the motor a few days ago because I was told I did not need it because it is the end of the line for the wires to the gauges I need. Can anyone confirm to me without a doubt that I don't need it?

In short:
1: Starter relay wiring help.
2: Is the PCM required for a carbed swap for the gauges to work?

Thanks in advance for your help and advice.

adsm08 · Oct 24, 2017

The key switches 12V to the relay. For your application what I would do is get a 2-wire starter, run the heavy wire right to the battery, and then trace the start wire out of the ignition switch. It SHOULD be red and blue, but it will be the only wire that is hot only in start. Then run that out to the small post on the starter. This will get the starter working, won't over-work the switch, and if you had PATS, should bypass that.

For your year you should not need the PCM for the gauges, as long as you left the wires that turn the IC on intact. The temp and oil pressure signals to the gauge cluster were not networked in 98, nor was the fuel gauge, those sensors are all hooked right to the gauges.

Ranger289 · Oct 24, 2017

Excellent, thank you for the quick response as well.

Now the motor came with trans and starter, it's an old school single wire starter. Now I might have to get a high torque starter to clear the headers I'm getting, but until then I'm going to try and reuse the original starter.

I'm going to have one last crack at wiring it with the multimeter tomorrow afternoon. Will post pictures of my setup then with additional questions.

Thanks for the help.

RonD · Oct 25, 2017

If you have 1 wire starter motor then you WILL need inner fender mounted Starter Relay(solenoid), like the old days
No 1998 relay in the truck can handle the amps needed for starter motor
Newer starter motors are connected directly to the battery via larger cable so smaller starter relay could be used

In 1998 when key is turned to START 12v will flow to/thru FUSE #24(7.5amp) in cab fuse panel, then out to clutch or trans switch(neutral switch) and then to Starter Relay in engine fuse box(tan/red wire)
You could tap starter activation wire at fuse 24 but would be by-passing neutral switch

If there is a factory alarm then there is also a Starter Interrupt relay in the dash that comes after Fuse #24 but before Neutral switch

Battery---------ignition switch-----------fuse24-----(alarm)-----neutral switch--------starter relay(engine fuse box)

As said the starter relay in the engine fuse box can only pass about 30amps so can not be used to power the starter motor itself, it is just to activate built-in starter solenoid on the new motors
So you either need to get a fender mounted starter solenoid(new battery cables) or a newer starter motor

Ranger289 · Oct 25, 2017

Hey guys, thanks a lot for the help so far. Turns out I'm not a complete fool, and the fuse box isn't actually the Ranger fuse box, it's an Explorer box. ie: The fuel pump relay is where I thought the starter relay was. In short, I had to cover my driveway in fuel in order to find that out. However, seems like I'm in the clear for wiring now with that knowledge.

I knew I'd need that solenoid so that's already mounted and halfway wired. Just need to lengthen the battery cable to reach it and we're good to go.

I'll post some pictures of the install later this evening. Thanks again.

289 Carbed swap wiring

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