Mechanics

TRUCK WON'T START

1996 Dodge Dakota • 6 cylinder 2WD Automatic • 105,000 miles

I have a 1996 dodge dakota that won't start or stay running because of a pink 30amp fuse called an auto shutdown fuse keeps blowing, Any idea what can be causing this?
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Iggy1234
January 25, 2011.



That fuse feeds the injectors, ignition coil, alternator field, and oxygen sensor heaters. Start by looking at the O2 sensors to see if any wires fell onto hot exhaust parts and grounded out. That fuse may also feed the fuel pump through the ASD relay or a separate fuel pump relay, (I can't remember).

If the fuse blows instantly, I have a procedure for locating the short.

Caradiodoc

Caradiodoc
Jan 25, 2011.
Fuse don't blow instantly, and I didn't find no burn't wires

Tiny
Iggy1234
Jan 25, 2011.
The closest book I have is a '99 book but it should be similar to your truck. The fuel pump is on a different fuse and totally different circuit, so you should still hear it hum for one second each time you turn on the ignition switch. That leaves him out as a suspect.

The alternator isn't likely to short intermittently. The 12 volt feed brush could potentially be damaged during a repair attempt but even that is hard to do. I would not suspect the alternator, at least not until everything else has been ruled out.

That leaves the ignition coil and one of the injectors as suspects. The fuel system leak detection pump and oxygen sensor heaters are on a different fuse, fuse "A", a 20 amp after the ASD relay. That would be the one that would blow if the problem was with those items. That circuit won't stop the engine from running. Since this is an intermittent problem, you might consider removing that fuse, then see if the 30 amp fuse still blows. If not, it could be because the 20 amp circuit is shorting but the 30 amp fuse is blowing because it has more current running through it for other stuff. Removing the 20 amp fuse will cause the Check Engine light to turn on, and fault codes will be set in memory, but you should be able to drive the truck.

If the fuse that's blowing is the 30 amp fuse "3", that pretty much leaves the ignition coil and one of the injectors. Chrysler has very little trouble with injectors so I guess I'd head for the coil first. No professional likes throwing random parts at a problem but if you have another coil to install, you might try that first. Another plan of attack would be to remove the dark green / orange wire from the coil's connector and use jumper wires to hook in a 10 or 15 amp fuse. If the coil is causing the problem, that's the fuse that will blow.

The only other place that circuit goes is back into the Engine Computer so it has proof the ASD relay turned on. If the 30 amp fuse still blows, we can rule out the coil. I think I'd be looking for a wire someplace that's rubbed through and grounding out. If you can make the fuse blow by wiggling and moving wiring harnesses around, remove the fuse and use jumper wires to replace it with a 12 volt light bulb. Brake lights work well. The bulb will be full brightness when the short is present in the circuit. The coil will have to be disconnected because it is normally grounded by the computer. Woops. I have to back up here. Put a new fuse in, then put that brake light bulb in place of the ASD relay. That relay won't stay on by itself unless the engine is running. Check the coil first, then if that doesn't pan out, I can provide more details on the light bulb trick.

Caradiodoc

Caradiodoc
Jan 25, 2011.
I can't hear the fuel pump hum at all, it won't make no sound when I turn the key to the run position. So I pulled the fuel pump relay out and turned the key on again and the new 30 amp fuse blew instantly.

Tiny
Iggy1234
Jan 28, 2011.
Dandy. That means the short is there right now so maybe we can find it. Rather than installing a new fuse, use a pair of thin spade terminals in the socket and a pair of jumper wires to connect a 12 volt light bulb such as a brake light bulb. It should be full brightness. If it is, now unplug the ignition coil and the injectors to see if the light goes dim or out. If you unplug something and the light goes out, you just unplugged the shorted item.

Caradiodoc

Caradiodoc
Jan 28, 2011.
I unplugged everything in sight and the light bulb continues to burn bright. Is there another way?

Tiny
Iggy1234
Jan 30, 2011.
That just leaves the wire harness and the Engine Computer. I would be real surprised if it was the computer, but unplug it just the same to rule it out. The black plug is the one with the wire from the ASD relay.

There is a harness that goes to the engine. It feeds the injectors, coil, and alternator field. I can't remember for sure, but I think the O2 sensor heaters are in a different harness but they're on the same circuit. Wiggle them in various places to see if your test bulb flickers. Since the fuse was blowing intermittently before, a rubbed through / grounded wire in a harness is more likely to be the cause than a component failure.

Caradiodoc

Caradiodoc
Jan 30, 2011.
I unplugged the computer and the light went out. I hooked in a circuit breaker fuse (20amp) and the truck runs with it. Is that safe to drive to the part store and back? I did notice a fuel line that can have a small leak. Do you you think if I replace the line the fuse will stop blowing? And how do I get my check engine light out now?

Tiny
Iggy1234
Feb 13, 2011.
Fuel leak is not related to a blowing fuse. How can the engine be running if the computer is unplugged?

Caradiodoc
Feb 13, 2011.
Remember the fuel leak detection pump you mentioned previously?You said the 20 amp fuse could be shorting out and making the 30 amp ASD fuse blow. And yes, I forgot to mention that I plugged the computer back in.

Tiny
Iggy1234
Feb 13, 2011.
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