1998 4L shutting off

[pgman]

Hi everyone.

I hope the moderators do not ban me for doing this, but I posted the following in the "misc. electrical" department earlier and I didn't get any action there. I thought it might do better here. Normally I wouldn't do such a thing, but this is my primary vehicle and both my mechanic and I are quite stumped. Anyway, here is what I've got:

1998 Rangee XLT supercab 2wd - 4L v6, automatic transmission.

Accelerating from a stop while making a left turn is blowing the #9 fuse under the hood. This is the fuel pump / RAP module fuse. I thought it might have to do with the engine pinching a wire when the chassis is under that specific combination of loads. However, I can't find any wires anywhere near the engine or transmission that would be in the way - even if I DID have a broken motor mount (I'm pretty sure I don't). I can recreate this problem if I put the transmission in drive, hold the brakes and rock the motor using the throttle. It would seem that the motion of the powertrain, relative to the chassis is causing this, but I can't find any harnesses / connectors / wires in harm's way.

Any thoughts /experience with this would be greatly appreciated. Thank you in advance.

BTW, I used to be a memeber here a long time ago and then I dropped off just because I got busy...AND because this Ranger of mine has been so reliable. I haven't had a single major issue with it until now. It's a shame they don't sell these things anymore.

 

[Earl43P]

I'll give it a shot....

Output from fuse 9 goes to the Fuel Pump relay contacts (on wire color LB/OG in the UHJB).

From therre it comes out of the fuel pump relay on the DG/YE wire and splices off to the PCM Pin 40.

Other end of splice goes to the Inertia switch, still DG/YE.

Out of the Inertia switch, it turns into PK/BK wire and travels through connector C309 (big square plug under the driver seat) all the way back to the fuel pump.

You might want to clean up ground G201, which is located under the passenger side kick panel, IIRC. Coincidentally, the RAP module is also located under there.


As an Electrician, I highly suggest you idle the truck and forcefully manipulate the wiring routes described above, until the fuse blows. Ford calls this a wiggle test and it can be invaluable finding a problem such as you described.

Good luck and welcome back to The Ranger Station!


The RAP Module portion of that power circuit splices off (in the UHJB) from the LB/OG wire to a WH/LB wire.
That wire then goes through connector C136, remains WH/LB to the RAP Module. C136 is located directly next to the UHJB (under-hood junction box).

 

[pgman]

Thanks for the ideas. Since this really does seem to be related to the engine movement, I was inclined to think it might be a chafed wire in one of the harnesses. Still, it is easy enough to take that kick panel off and start looking around in there. I agree that the "wiggle test" is the way to go. That's my next plan - now that I know it is definitely related to movement in the chassis. My buddy has a circuit breaker drop in "fuse" on a tether. I am gong to borrow that this weekend and see what I can find. It's a pain to keep replacing fuses while I troubleshoot this...it's very annoying.

I know it's got to be something stupid simple. I just have to dig until I find that broken, chafed or misplaced wire.

 

[pgman]

Problem solved



This has to be the silliest thing - but we found the trobule this evening and it's all fixed. It turns out the pink/black wire (to the fuel pump) had been rubbing against the floor of the cab. This wire passes through the cab floor (along with numerous others) to two connectors, which are mounted to a plastic bracket. The plastic bracket then bolts to the frame. Unless you know it's there, it is rather difficult to locate these connectors. The bracket holds these connectors up tight against the floor, out of harm's way. However, the ONE wire (the pink / black fuel pump wire) had apparently been rubbing against the truck floor for so long that it made it through the insulation and began to arc against the floor. When the arcing became bad enough, the fuse blew and it was game over, dude.

The funny thinig about this is that, on the day the first fuse blew, I noticed a clicking / ticking / popping sound in the radio speakers. I didn't think a whole lot of it at the time, but after seeing the underside of the truck cab (where the wire was arcing and scorching the metal), I now know what was causing the noise in the radio. This is one of those screwy electrical gremlins that cause some people to ditch a vehicle and go buy a new one. I am glad I didn't do that - though I must admit the thought crossed my mind.

The one thing I have to say, though, is that I can never complain about this truck. This is the first time it has EVER left me stranded anywhere in over 170,000 miles. I know, tomorrow it will blow up on me! Still, if a meteor fell on it tonight, I'd go buy another one tomorrow - too bad it wouldn't be a new one. I've had some VERY nice cars in the past, but I have to say that the Ranger is, hands down, the best vehicle I've ever owned. It's cheap and easy to repair and I've never felt like I couldn't trust it (save these last two weeks). Now that I know what was causing the mysterious electrical problem, I have no fear of trusting it once again.

Thank you for your help (you know who you are).

 

[Earl43P]

Like the late Paul Harvey used to say, "and THAT'S the rest of the story".

Good job tracing that down!