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Getting stranded in my Ford F150!

I am desperately hoping someone will have a suggestion for me. I have had my 1995 Ford F150 to three different mechanics at three different shops and no one can figure out the problem with this truck. After I drive the truck for 25-30 minutes and then turn off the engine, it refuses to start again. The engine cranks and cranks but will not turn over. Sometimes after it sits for 45-60 minutes, it will start up again. I have replaced the starter and the rear gas tank and rear fuel pump (it has dual fuel tanks). The mechanic who replaced the gas tank and fuel pump replaced them both a second time after the pump pressure was discovered to be too low on the new pump. However, I still I get stranded almost every time I drive it, so now it is just sitting in the driveway. All three of the mechanics kept the truck for about 2 weeks and tried letting the engine run for as long as an hour, but it always started right back up again for each of them - even after multiple tries at turning off and then restarting. Does anyone have any suggestions for what might be causing this problem? Many thanks!

Maybe fuel isn’t the issue anymore - Are you sure you’re getting spark?
You could get a cheap spark tester (any automotive place or harborfreight) that you plug in series with a sparkplug. If there’s spark, the tester will flash.

Here’s one:

This truck should be a TFI model so the ignition module is always a suspect. Symptoms vary, there may be no codes in memory, and testing those modules is often a waste of time because they may be faulty and still test good.

Given that you need three things–air, fuel and spark–in the right amounts/right time to run, I wonder about using starting fluid for diagnostic purposes.

The next time you fail to start up, squirt some starting ether up the snorkle inlet to the air filter box. Then get in and crank it. If it fails to run (for a second or so, at the least), it’s not likely a fuel delivery problem.

Then, try to hook up an inductive timing light to a plug wire to check for spark.

If you’ve got fuel, spark–but no run, then you’re looking at stuff like air obstruction, mis-routed plug wires, etc.

Thank you very much for your suggestions! This is very helpful!

I appreciate you taking the time to offer this information! Thank you!

There is a fuel pump in each tank plus another under the cab. Which pumps were replaced? If an in tank pump fails but the under cab pump is working, switching to the other tank should enable the engine to start. It may be worth the cost to invest in a EFI pressure test kit to determine if fuel pressure is the problem.

You need to test when it fails to start. Of course thats when it is not at the mechanic. Given a ford with an ignition module I might just replace the module. As others noted testing is not going to reproduce your specific non start issue. I think this sits on the engine like my taurus module does. So even idling may not get it hot enough to act up. It is a chunk of change but easy to do.

as stated by others here i would bet money on the ignition module. been there done that.

The module is relatively cheap and easy to replace. If you want to shoot from the hip that’s the best shot you can make.

As euryale1 wrote:

You need to test when it fails to start. Of course thats when it is not at the mechanic

That means you need to do some preliminary troubleshooting yourself.

Get the spark tester @Remco mentioned, and some starting fluid, and enlist an assistant capable of turning the key while you watch for spark. Then head off on a mission to create the problem. When it occurs, check for spark first. If you confirm you are getting spark, do as @meanjoe advised with the starting fluid. Then you’ll have clear data for your mechanic to use for solving the problem. Your mechanic may want to set you up for a way to check the fuel pressure when it won’t start, so you may want to check with him before you embark on this excursion.

FWIW, a terminology clarification: if the engine “cranks and cranks”, that is the same as “turning over”. You have an engine which will turn over but not start. You are on the verge of solving that.

PS: you might also want to bring along something for you and your assistant to use for amusement while you are “stranded” waiting for your truck to cool down and revive itself. Maybe a picnic lunch, easel and paints, travel brochures, a book of poetry, a pile of old mail to sort, car wax and some rags, old photo albums, etc.

It’s the hall effect sensor in the distributor. It gets hot and fails. Buy a new distributor for $95. Takes hour to replace. Just did it on my truck. It only stalled or wouldn’t start when the AC was on and heated up the sensor.