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1991 Explorer won't start


March 9, 2012
Reaction score
City, State
Yakima, WA
Year, Model & Trim Level
1991 Explorer XLT
The engine turns over normally but will not start. Fuel pump cycles normally and there is plenty of fuel pressure at the rail. If I spray raw fuel, carb cleaner or starting fluid into the intake it tries to start but doesn't. Repairs so far:

1. Replaced ECM and fuel pump relays.
2. Replaced fuel filter.
3. Replaced check engine light.
4. Replaced computer.
5. Replaced the battery.
6. Checked all fuses, relays and grounding points.

What are the chances it's the ECM (ICM) located near the battery? What else might be the issue?

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Check for spark. Connect a spark plug to a spark plug wire, touch the plug threads against ground like the block, crank engine and check for spark across the plug gap.

The ICM is not a common failure point on these trucks. Check for spark as described above. If there is no spark, perhaps the ICM is not seeing the required signal from the crank position sensor, or one of the ICM inputs is damaged.

You need 3 things for a combustion engine to run.

1) Fuel
2) Spark
3) Air

In your case, you're missing spark. As Arco pointed out, the ICM (Ignition Control Module) isn't a common failure - which is good because a new one is several hundred dollars. The quick and dirty spark check Arco also mentioned a good starting point. If you don't get any spark using that method, then my first thought would be the ignition coil. It's the big black block mounted on the left (looking at the engine from the from of the vehicle) side of the intake towards the rear of the engine....it's easy to find...just follow a plug wire from the engine back to the coil.

Check back with us after you do this test and let us know if you have spark or not.

My bad, as the kids say. We have plenty of spark. Sorry I didn't mention that before. I'd best add that it has a new air filter element as well.

What's been puzzling in this whole affair is how it stopped running. The truck was idling at a stop sign and simply died. There were none of the usual indicators of jumping time or anything of the kind. It just died.

For S&G's, check the inertia switch under the carpet on the passenger side footwell up by the firewall.

As Iron Weasel said, fuel+air+spark. And compression, of course, but I doubt you've lost that. The only way I would expect you to lose compression immediately is with timing chain failure (uncommon) and you can check compression with a tester pretty easily to rule that out.

The inertia switch is likely fine if the fuel pump is operating, and priming the system.

Check that the injectors are operating. The PCM cycles them using 12v pulses at their connectors. A noid light set or 12v test light can be used to see these pulses when you are cranking the engine. I hooked up a simple 12v bulb I had lying around to an injector connector and it worked great. Another way is to use a mechanics stethoscope to listen for the clicks of each injector opening and closing.

Thanks all for your posts. I didn't read them until this evening. By way of an update we went a bit "old school" and used a spray bottle with fuel in it to run a check. (I hate starting fluid on gas engines) The engine runs fine as long as you keep pulling the trigger. As mentioned, I'll check for 12v at the injectors. Considering all the items I've replaced (mentioned earlier in the thread) what would cause a no voltage issue at the injectors?

And many thanks to all who have responded.

Not to offend, but I gotta ask...when you say "plenty of fuel pressure", are you seeing lots of fuel spray out of the test port when you depress the valve, or did you use an actual fuel pressure gauge to get a reading of (at least) 30 psi or more?

If your pressure SEEMS to be good (20 to 30 psi) it will never start or run.

At this point nothing is offensive. ;) No, I'll have to rent a gauge to properly test that. Cycling the fuel pump and then depressing the valve with the key off yields a fuel discharge that sprays beyond the engine compartment.

Not sure what it will cost you in your area of WA, but get ready for the price on the rent a tool fuel pressure tester... it cost me $120 with tax in little podunk Oklahoma where I live. I had to rent one a few weeks ago for another vehicle... needless to say they had the rent a tool back within the hour.