ok, sorry for this being my first post but I'm kind of in an emergency here.

A friend of mine gave me a '95 ford ranger because it kept popping the 30 amp ignition fuse(located in the fuse block under the hood by the windshield, drivers' side.)

Now here's the deal, first of all, the key lock cylinder that was in it was worn almost completely out, to where you could start it without a key. I've since replaced that (that did not fix the problem). the guy that gave it to me was tired of buying the big 30 amp fuse for it, so he made a jumper wire to plug into the fuse slot that allowed him to run the small cheaper 30 amp fuses.

when I first drove this truck, I tried to take it around the block from where it was parked. it started up and ran just fine. then, when I put it in gear and began to pull away, it would burn the fuse and shut the truck off. all of the electricals still working, but no ignition fire to the engine. I replace the blown fuse, it starts right up.
so, again, I try to take off, and get about 10 feet, it trashes the fuse and dies again, and will not start again until I replace that fuse.

it always kills the fuse right about the place where the clutch is almost completely released to go into drive.


what is the problem with this thing?

 

Could be many things. Personally I would just start looking over all the wires, see if anything is frayed. Check your ground as well.

 

nothing is frayed, ground is good. the jumper wire he made to use the smaller fuse did get kind of hot the last time it went, but now it won't even start with a good fuse in there. I pulled the fuse block to check for a burned off wire, and all the wires look good. the only thing is that where that particular fuse is located, there's no wires going to it, it's just a large metal plate.

 

ttt

 

is this tranny manual or auto
if it is a auto ( you put it into gear , the fuse blows )
start looking at the various electric connections that are connected to the auto tranny
steering column, side of transmission

 

It sounds like your blowing the PCM Power Fuse (30A located in the BJB). This fuse supplies power via the PCM relay to the PCM, Camshaft Position Sensor, Fuel Pump Relay, Fuel Injectors, Purge Flow Sensor, EVAP Purge Valve, EGR Vacuum Regulator, MAF Sensor, and IAC Valve. To start I’d recommend searching the forums for PCM Fuse etc. as I believe there has been posts on this topic before. If nothing comes up, you’ll need to start checking all associated circuits and wiring looking for shorts.

 

it is a manual transmission. also, the fuse that keep popping is located right in front of the drivers side under the hood. I've removed that fuse block from it's base and looked at where all the wires from the harness go into it, and where that fuse is located, it doesn't appear to be any wires going to that area, it just has a large metal plate underneath that whole area toward the top (front) area. all the wires from the wiring harness connected to the fuse block are located lower and don't appear to have anything to do with that particular fuse or the ones immediately next to it.

 

Look in your owners manual under Servicing Your Ranger for a diagram of fuses. If you don't have the OEM Manual look at this link ford owners manuals. It only goes back to 1996 but should get you in the ball park starting on page 309.

The short you're looking for is more than likely going to be found somewhere along one of the the wiring harness in the engine bay not in the Power Distribution Box.

You can rule out ground circuit issues right off the top. A short on the ground side of a circuit will not cause a fuse to blow.

Carefully follow the wiring coming out of the Power Distribution Box along the firewall crossing over to the engine and all listed items within the engine bay. Pay particular attention were wiring wraps by brackets or mounted items that may have pinched wiring during a past replacement.

If all wiring under hood checks out ok, look under dash around the E-brake, clutch, or brake pedals. Next place to look would be under cab (drivers side) and along frame rails back to the fuel tank.

 

Thanks. I've gone through the engine bay and checked everything I could see. nothing looked pinched or disrupted.

the key lock cylinder in the steering column was pretty jacked up to where you could get in it and start it without a key, could something be shorting out inside the column?


whatever this is, it seems to be only shutting down the electricity to the firing system when the fuse goes. everything else is working.

I looked at the diagram, and the fuse that keeps popping is the PCM power fuse.

 

No the ignition is powered by a different circuit/fuse. Nothing in the column would cause the PCM fuse to blow.

The PCM Power Fuse supplies constant power to one terminal of the PCM relay, both of which are located in the Power Distribution Box. Turning the ignition to on/start position simply activates the PCM relay. Once its activated it allows power to flow from the 30A fuse through the relay on to the above listed components.

You either have a power feed wire intermittently shorting to ground or one of the listed components is internally shorting to ground. Unfortunately there is no easy way to figure this one out. It comes down to a process of elimination one step at a time starting with a close visual inspection.

You could also try installing a test light in place of the fuse. Turn the key to on. The test light should light up. Start wiggling the wiring while watching the light. If the light starts to flicker or goes off your close to where the problem is.

 

I don't think a test light will work. the last time it got hot, it didn't blow the fuse, but the engine will not start. it turns over just fine, but there's no power going to that fuse port now.

 

I really appreciate everyone's help with this.

Ok, a few questions, is it possible that the PCM relay was initially going out, maybe causing it to send backed up power through the circuit to the PCM fuse that was making it burn? And since there's no power to the PCM fuse terminal now, is it possible that I've completely cooked the PCM relay? Does the power go through the PCM relay before it makes it to the PCM fuse terminal?

Also, do you think there might be something inside the PCM itself, causing all this to happen?

I apologize for all the questions. : ( I'm just glad I finally found people out there with brains..lol

 

Ok, an "update" to my situation here:

I figured out that the last time the PCM system heated up, it had fried the PCM relay located in the PDB. So, I replaced that with a new one, and it will start and run now. Although, it's still popping fuses when I try to drive off.
From what people have been mentioning to me about the NSS (neutral safety switch) I located it, and I guess I can rule it out as a culprit, because as an experiment, I started the engine, then unplugged the 6-wire connector from it, the engine still ran, but exhibits the exact same symptoms without it even being connected to the loop.

However, I can't seem to get it to pop the 30 amp PCM fuse when I let off the clutch to go in reverse. It only happens when I'm letting off the clutch to drive forward. I thought it might be the two sensor plugs connected along the side of the aft area of the tranny, so I tried unplugging those one at a time, then both of them at the same time, exhibiting the same results.



running out of ideas.............

 

does your rear axle have a sensor bolted to it ( gear case )

it is possible that somehow it came loose and being ground against the inside ABS ring

as soon as you start rolling --- the positive,ground, and sensor wires are all being grounded against each other

just a thought

 

No power goes to the ABS sensor, it generates a low level signal that goes to the PCM.

 

I will look and see. but if that's the case, then why wouldn't it do it taking off in reverse? it only does it when I try to drive forward.

 

find the wiring harness that runs along the driver side inner fender well
remove all of the electrical tape you can you should find a positive and negative power wire that have had the insulation ground off ( partially )
i asked a ford mechanic about this ??
he said that the wiring harness is clipped to the metal inner fender ,, and when you mash on the gas ,,the engine pulls on 1 half of the harness ( 2 halfs of the wire harness rub against each other inside of the bound electrical tape ) and arch against each other

 

wow, I really appreciate you going out of your way to ask around and help. I will check that out. I have already looked at that harness, but I didn't remove any tape from it, as I didn't see a "rubbed" area anywhere. but I will take the tape off and look. thank you very much.
why exactly does the engine "pull" on those wires?

 

i am not excatly sure

but me thinks the wiring harness is not long enough to allow totally free movement of the harness

when an engine is suddenly put under a load , it will twist violently to the left
( when you sit in the drivers seat )

engine turns counter clock wise, the rotating mass twists the engine in that direction

 

well, I finally found the gremlin, I don't know for sure what this thing is called, but I think it's an EGR sensor plug. it plugs into a vaccuum hose coming off the engine. Apparently, the positive wire going through that particular cluster of wires, had is insulation worn though , causing the bare positive EGR sensor wire to rub against a high pressure air conditioner tube, and instantly pop the PCM fuse.

My "diagnostic" procedure basically consisted of me starting the truck while it's up on jackstands, and rolling under neath the vehicle using my skateboard as a "kreeper", and wiggling suspective wires around. (very dangerous, I don't recommend it, I was just at the end of my rope with this thing. I know it was very stupid, but I got the damned job done.) even though the problem wasn't under the truck, I had to rule everything out.

So, anyway, I really appreciate everyones help with ideas and possibilities, I've fixed the problem.

thankyou thankyou thankyou!!!!