Hello all, I came to visit my folks and help turn a wrench on their recent acquisition - 1999 Ranger 3.0 standard - when I found myself in the middle of an ongoing battle with fuse #24.
The shop put a brand new starter in a couple days ago. My father replaced the clutch position switch and put in a brand new relay in the under-hood fuse box.
Following a wiring diagram, at the mechanic's instruction, i ran a brand new 16 ga wire from the dash fuse box to the clutch switch and from the clutch switch through the firewall to the under-hood fuse box a few inches from the relay.
No corrosion on any of the points of contact.

Now the symptoms:
Vehicle starts fast and purrs like a kitten when key is turned. Drive into town, to the store, whatever, and shut it off. The shortest trip I've taken is about 1/2 mile. Go inside, do your business (maybe 30 minutes on that 1/2 mile trip), come back out, turn the key, and the fuse pops. Swap the fuse out and it will start right up.
My gut instinct is a short to ground but... Why would the first fuse blow and not the second? The second fuse will blow on the next trip out, assuming you start the vehicle while warm.

The guy at the shop tested for about 5 hours with and without starter or false load, unplugged this, tried that, and came out swearing he could pop a fuse every time or never based on holding the wiring harness under the dash a particular way.
Any input is appreciated.

Edit 1: my father says he has sat and cycled through five fuses in a parking lot, waited 20 minutes, then got it to start with a new fuse. He's also experienced the "pop one fuse, replace, start up" condition.

 

More information learned throughout the day:
Started the truck, ran it for 5 minutes, turned it off. Several hours later attempted to start it again and the fuse blew.

In addition, there is a check engine light on. The only code stored is P0453, which comes up elsewhere in the forum as being a fuel tank pressure sensor issue.

I've noted in my investigation previously that at the clutch position sensor, a second wire tees off the connection running to the relay through the firewall.
According to a wiring diagram I found, that wire should be running to the fuel tank pressure sensor.
Would LOVE any insight before I go tearing the bed off or dropping the tank needlessly.

Handheld OB2II reader displaying a P0453 fault code.

 

I have removed the fuel pressure sensor from the vehicle but would like to do testing on it before jumping to replacing an $80 part for no reason. With no shop manual, I'm at a loss for how it functions or should be tested.

 

Just tried starting the truck with the sensor disconnected and STILL blew a fuse (abnormal behavior on a cool morning)

 

Tested continuity to ground on fuse 24 with pressure switch unplugged (ignition off) and found continuity.
I unplugged the connectors under the cab that runs to the rear wiring harness and still found continuity to ground.

 

Traced short to what seemed like the floor wiring harness, though I must have been misled, or else the car is full of shorts. Not sure.
Bypassed the tan/red wire from clutch switch out to floor port and still have a short on the far side of the new run.
Not sure how to test the pressure sensor, but found continuity to ground in the brown/white wire on the far side of the fuel tank pressure sensor.
I see that wire runs to the door sensor (left side of engine) and/or the TPS (top left, front of engine, on throttle body)
I'm so frustrated.

 

Found the engine wiring harness to have fallen off or been removed from it's mount and drooped onto an exhaust tube on the driver's side of the engine.
That exhaust tube is covered with some fiberglass tape, meaning the wiring wasn't damaged, just the plastic melted, but it's still not GOOD that it happened. Continuing the investigation...

 

I have now started the vehicle 15+ times under various conditions without blowing a fuse.
The solution was to tape the melted wire from the engine wiring harness which had begun shorting out onto the exhaust component after wearing through the fiberglass wrapping, then bolt the harness up to keep it off the connector.
I'll update here if the fuse begins blowing again, but as I'm in the middle of an intensive wiring project, that may be a few days.

 

As a final update, the fuse problem has been seemingly resolved without further troubleshooting.
The trouble code remains even after a sensor replacement, suggesting shorted wires or a damaged PCM.
Hopefully this helps someone in the future. If not, oh well.

 

Just now reading your multiple entries on this problem. I think it might have been a good idea to open up that melted harness as something in there definitely has been shorting out. Might have found some insulation on a wire that is gone and exposed the wire itself. Perhaps seal the individual wire or wires and then tape and secure harness. This yo keep green crusties from forming on the wires. But good job and good troubleshooting. Maybe you could find a set of shop manuals like I did for my 2000 Ranger XLT extended cab. Those two booked cost me $65 on ebay snd are a godsend in my keeping my truck in good condition. Good luck and thanks for good postings.

 

Thanks @TBone26 . I may go back and revise my post. The past two weeks have been a bit of a blur.
My father (not mechanically inclined) purchased the truck for my brother (not a self-starter) and I was merely a visiting mechanic for a fortnight. If I have to do more work on it in the future, I'm throwing his Haynes manual in the trash and getting OEM, and an OEM wiring diagram manual to boot.

As for the wiring, I originally just hung the harness out of the way as a temporary measure, but went back to inspect it more closely and found (surprise surprise) my particular wire to not just be on the bottom of the harness, but the only apparent wire that had managed to melt through in a particular patch (dark garage made inspection inaccurate) was, of course, the wire running from the fuel tank pressure sensor. The copper was clean and not frayed, and I saw now signs of damage to the neighboring wires, so I wrapped the single wire in electrical tape, then re-wrapped the harness section I had unwrapped and hung the harness back out of the way.

 

I apologize for the zombie thread here...
The Ranger has been returned to me, check engine light still present. I looked at the cost of a matching PCM and they run upwards of $100, which is too expensive (in my opinion) to "throw parts at" an issue without proper troubleshooting.
When it stops snowing, I'm going to crack open the melted wiring harness and do a thorough inspection inside that. Beyond that and pulling out a code reader, does anyone have advice on troubleshooting this particular issue?