93 Ford Ranger 3.0L v6 - EEC 30 amp fuse keeps blowing

[StrangerFordRanger]

I own a1993 Ford Ranger 3.0L v6, that has an electrical issue, the EEC 30 amp fuse (#4) keeps blowing as soon as key is turned to ON. From what I understand this is on circuit 361, so I need to start unplugging components on this circuit one at a time. Does anybody know specifically what components sit on this circuit?

 

[Uncle Gump]

I'd be looking for more of a direct short to ground on the output side of the EEC relay.

I don't have those schematics... maybe @ericbphoto does.

 

[Curious Hound]

I'd be looking for more of a direct short to ground on the output side of the EEC relay.

I don't have those schematics... maybe @ericbphoto does.

Remind me when I get home from work tonight. I’ll post pics from the EVTM.

 

[StrangerFordRanger]

Remind me when I get home from work tonight. I’ll post pics from the EVTM.

Eric, just checking in, with that friendly reminder. Thanks any help you can provide.

 

[Curious Hound]

I should have mentioned that I work 12hr shifts and also had to drive across town to pick up my dog from my ex (shared custody of the dog). Anyway. Here's your homework assignment. If the fuse only blows after you turn the key on, that means it is a circuit that is fed through the pcm power relay. So, you will be tracing out all the stuff fed from the red wire (361) coming off that relay. Easy things to rule out would be to unplug the fuel pump relay, unplug the MAF, unplug the purge canister solenoid, the egr vacuum regulator, the idle air control valve, and then the injectors. If auto trans, also unplug connector 120 at the transmission.

 

[StrangerFordRanger]

Eric, hope you didn't have to work too hard on a Sunday. Thanks!! great instructions!! This helps a bunch!!!

 

[Curious Hound]

Eric, hope you didn't have to work too hard on a Sunday. Thanks!! great instructions!! This helps a bunch!!!

Just follow that red wire. Somewhere there is a bad component or the wire is rubbed through and shorting to ground.

My workload wasn't bad today. I'm a maintenance tech in a BMW manufacturing plant, in the paint shop. We are usually shut down for cleaning and maintenance on Sundays. So, it's an easier pace than production days.

 

[StrangerFordRanger]

@ericbphoto

So, I just finished unplugging all of the components that you listed above and re-tested by turning the key ON and the fuse still blows. Also, I looked at the red wire at various connection points and didn't see any rubbing or damage. What other components should I unplug next?

 

[Curious Hound]

If I understand correctly, it doesn’t blow the fuse unless the key is turned on. Correct?

What if you remove the pcm power relay?

If it still blows with the pcm power relay removed, connect everything back together and unplug the big connector at the pcm and see what happens.

 

[StrangerFordRanger]

Correct, it only blows when you turn the key to ON.

No, the EEC fuse doesn't blow when I remove the EEC Power Relay (#23).

 

[Mechrick]

That's the VPWR circuit that powers up all the injectors and any relay/solenoid that needs 12 volts. Check/unplug the canister purge solenoid, the mass air sensor, the transmission harness and check the harness where it runs to the injectors and transmission. Something shorted somewhere...

 

[StrangerFordRanger]

So, I need to check the harness that run to the above components. When you say "check" you mean check for damage, or burned, or a broken wire?

 

[Mechrick]

You are checking for a short to ground. Shorted component, harness rubbed through, oil-soaked wire insulation falling off, etc.

A neat trick is to wire a halogen headlight bulb with spade connectors and plug it in where the fuse goes. When you turn the key on and the PCM power relay engages, the headlight will light up and only go out when the short is removed. You can unplug components, wiggle harnesses, etc. while watching the light.

 

[StrangerFordRanger]

Yep, I have been doing the headlight bulb trick for the last couple days, but I will keep wiggling the harness and looking for damage the wiring harness.

One other note, that may help, that could be related:

The last time the normal fuse blew before I replaced it with a 30 amp circuit breaker fuse, I was able to check the CEL with a ODB1 reader and I got the following codes:

513 - Internal voltage failure in the PCM. (I assume this is related to the EEC (30 amp) fuse blowing, initially.)

566 - 3/4 shift solenoid circuit hard fault. (I know this is related to me losing overdrive (OD) recently. The last time I successfully drove it before the EEC fuse issue).

 

[Mechrick]

As the 3/4 solenoid is one of the circuits powered up by the VPWR circuit, I'd start there. Slide under it and unplug the trans harness and see if the short goes away...