1991 Mighty Max (Montero) not starting

Maintenance/Repairs
1

I’m trying to help my daughter troubleshoot her farm truck. It’s a 1991 Mitsubishi Mighty Max (which seems to be a Montero with a truck bed.) This is a V6 4WD and has the following very frustrating symptom: It won’t start when SHE tries it! It will crank just fine and never start. When I try it (or even LAY MY HAND ON THE HOOD) it will start! I think the beast just doesn’t like her. When this is going on it seems to have spark (she pulled a wire off and connected a spare spark plug), so I’m guessing that it’s a fuel delivery issue.

I little history, this truck came from AZ and when being driven across the country it blew MANY fusible links under the hood (particularly bad in the west where it was really hot) but has only had that happen once in the 2 years it’s been in NY. It’s had a new (rebuilt) ECU installed to no change. (and in fact the rebuilt failed totally until we found a bad solder joint in the unit and re-flowed it).

We’ve discussed replacing the crank position sensor, but I’m not sure how it could be intermittent. I know you’re thinking “hey bozo you already replaced a very expensive ECU….” but that was before we found the fusible link so it appeared totally dead. Is it worth replacing the crank sensor on spec? Could it be intermittent?

If it is fuel delivery as I suspect, what can I set up to measure this in the field?

Any other good thoughts?

THANKS!

2

Without a factory wiring schematic and knowing which link is blowing I’m afraid that I can be of little or no help.
You might consider registering on the AutoZone website, follow the prompts on vehicle type, and then go to “Repair Info”. Go through Chassis Electrical and then on the left will be Wiring Diagrams.

Those are not terribly precise but can provide a little info at least.

It’s possible that if the fuel pump is on the same circuit as the blown link that the pump is dragging or intermittently seizing and which is then causing high current consumption; enough to pop a link.
The fuel pump current could be measured with an ammeter and that could provide some insight.

Without knowing what all is on the circuit on whichever link is involved that’s the best I can do.

3

Next time it doesn’t start, squirt starter fluid in the throttle body. If it starts, it’s a fuel issue.

4

Since it starts ok for you, but not for your daughter, think about what’s the difference. You could be twisting the ignition key with more force, or from a slightly different angle. So it could be a faulty ignition key. Are there any other things she does different than you when starting? Does she pump on the accelerator first, same as you, etc? The starts-for-you-but-not-for-her thing may provide some good clues to the problem, so exploit it.