Let me give a brief history: Currently, the car has 194000 miles on it. I put a tranny in it (I did the work myself) last may. The engine still runs really strong and the transmission is good too, so I want to keep driving it for a while before giving up on it.

At about 130000 miles the computer chip key reader thing failed and my parents (who owned it at the time) had the security thing bypassed (I think installed a resistor somewhere?) by a local mechanic who has since passed away.

It started fine until last december when it quit and wouldn't start and acted like it had no battery (no lights or anything). The car sat for 3 months until I resurected it 2 weeks ago to drive while my 1990 ranger was undergoing a 2.3T swap. I replaced the battery and that curred most of the problems except for once in a while when you'd go to start it, the dash (lights, gauges, etc) would go haywire when you turned the key to the "start" position. I figured the starting switch was going bad so I just ran a push button starter because I did not feel like wasting time taking the steering wheel and airbag out to replace the whole ignition switch cylinder.

So the car has started and drove flawlessly for 2 weeks now until yesterday when it all of sudden did the gauges go haywire thing while I was driving. The engine was spinning but unresponsive while this happened. Then it became normal again and I drove home. I shut it off and it hasn't been able to start since then. I smelled a burning smell outside the car (not inside) when I shut it off. I checked my push button starter wiring and all is well with that, but applying 12v to the starter solenoid won't engage the starter.

I started probing and found that the resistance between the positive and negetive battery cables (with the battery disconnected) is only 1.6 ohms with the ignition in the "run" position. I traced this back and found it is in the "ignition switch" circuit as the problem disapears when I pull that fuse from the underhood fuse panel.

Anyone have any experiences like this before? Are there any known problem areas where the wiring harness is prone to shorting out? Exactly where is the PCM on these things? I want to pull that and see if it contains my short.

I need the car to drive to school and work all next week. Please help me figure out what'* wrong with it. Thanks in advance

I'm not very good with electrical problems, but your PCM is at the very front of the car, on the driver'* side, encased in a black box.



It'* circled in red.
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Let'* start by disconnecting the battery terminals & give them a good cleaning. Remove the bolts & rubber boots to get at the corrosion. Clean it up with sandpaper or wire brush. Make sure you clean both sides of the cable ends & the spacer. We see this problem very often.

Before trying to start put a wrench on the alternator or crank pulley & see if the crank rotates. If not then don't try starting & let us know.

A good start would be to remove the positive and neg battery cables and grounds on the engine and clean them all, then apply dielectric grease.
The gages going haywire tells me there is a power continuity problem. The starter also may be dead. try tapping it with a hammer handle while someone jogs the key.

Update:

I already disconnected the battery. There is nothing wrong with the starter. The engine rotates freely. I already tested the battery cables, they're fine.

I also separted the different positive leads at the battery terminal. The starter and alternator leads are fine. The short is in the power distrobution lead.

The car has a dead short when the ignition switch is in the "run" position.

I've isolated the short to be somewhere between the load side of the two 60 amp "ignition switch" fuses under the hood and ground.

With the ignition turned to "run" or "start" the ohmeter reads 1.6 ohms between the positive fuse bus and ground with these fuses plugged in. If I pull the fuses, there is mega ohms of resistance between the positive fuse buss and ground, as it should be.

I've tryed pulling every fuse, circuit breaker, and relay under the hood and under the dash trying to isolate the short further. I also tried wiggling all the underhood wiring I could get my hands on while watching the ohmeter to see if I had some bad wiring.

Currently I have pulled the steering wheel and am in the process of removing the ignition cylinder. I am convinced the short is somewhere in the vicinity of the ignition column, as I've exhausted all the other places to find it.

Right now I have to put it to rest because I have a tough week at school and won't have time to mess with it anymore. I guess it'* back to driving the gas sucking exploder 80 miles a day.

I'll let you guys know what I find out eventually. Please share any other ideas you may have. Thanks

I've never checked for electrical problems by using your method. How do you know 1.6 ohms is a problem? Seems like a fuse would blow if you had a short.

Well, every other car in my driveway (2 rangers, 2 f-150s, a grand marquis, an explorer, and a chevy half ton) reads unlimited resistance between the battery cables with the battery disconnected.

Ohms are a measure of resistance between two probes. 1.6 ohms is practically a dead short. The reason that no fuse has blown is probably because there are two 60 amp fuses feeding the ignition switch circuit.

If anyone wants to do me a favor and disconnect the battery from their running bonneville and tell me what the resistance is that would certaintly help. But from an electrical engineering standpoint, 1.6 ohms between the battery cables = big problems!

Update,

After sleeping on it, I've reached a different conclusion. Since V=IR (from circuits 101), reading 1.6 ohms just means that there is a draw of 12/1.6 = 7.5 amps. This is perfectly acceptable and to be expected when the ignition switch is turned on.

I'm used to residential 120 volt circuits, where a resistance of 1.6 ohms is not acceptable, as there would be a draw of 75 amps. But with a little 12 volt system the resistances need to be low to get any current going.

All those other vehicles did read unlimited resistance, but I never switched the ignition on.

Thanks for challenging me, sometimes it'* easy to become convinced of a problem that doesn't exist.

I guess it'* time to start looking at the battery cables, starter, and engine grounds more closely.

I just went & tested the resistance of a #93 light bulb. That one bulb had a resistance 1.4 ohms. I'm kind of surprised that the ECM, ICM & whatever else powers up with the key on run aren't even less than that.

Check & see if you're getting 12 volts to the terminal on the starter that the small (purple?) wire is connected to. Someone has to turn the key to start for this check. Oops, I forgot you installed the push button.

It sounds like you might not have checked the battery cables because you thought you were dealing with a short. Don't overlook this simple check. It'* very very common to find lots of corrosion there.

I checked them for being shorted to ground, and they were not. However, I did not check for continuity or ability to flow large amounts of current.

On a side note, do you know where I could find a list of engine grounds and their locations?