1987 F150 stalled, no crank

1987 Ford F150, 302, 5.0L, automatic, 120k miles.

I’ve posted about my truck several times and this problem won’t go away. It stalls while driving. Replaced fuel pumps, EGR valve, map sensor, new spark plugs, relocated and replaced the ignition module, starter and solenoid, fuel pump relay, ecu relay, and nee (remanufactured) ECU. Drove fine over 4 days and 60 miles, no stalling. Started rough and a little sluggish, I blame me for not having the timing set right on the money. Drove 15 miles and it stalled in the driveway. It would very very slowly crank, then no crank after several attempts. I’m waiting for the tow truck to haul it to the old Ford mechanic. Any ideas what the car may be?

When it stalls do other electrical things also quit? I’m getting at possible intermittent battery internally, or battery connections - an internally corroded cable, for example.

Plus 1 to what shanonia said & are the idiiot lights coming on when it stalls?
Right now it sounds like the battery is dead. Check battery voltage and if it’s less than 12.6 volts give it a full charge, start it up and check charging voltage which should be around 14 volts.

Everything electrical works. When it stalled, the radio was still playing. The battery tested to be fully charged after it stalled, that was the first thing I checked (after flipping the interior light on and off)

Why did you RELOCATE the ignition module.???

I would suspect that the battery cables are so corroded that they cannot carry the current.
They are 30 years old???


Slow cranking means there some problem with the battery, battery connections, engine to chassis ground, or the starter is faulty. Of those a discharged battery, battery connections, or the ground problem could also cause engine stall-outs. Weird problems with the starter could cause engine stalls also, but much less likely. You need to get to the bottom of the slow cranking before moving on to the cause of the stalls. One caution about relocating the ignition module, that part handles quite a bit of current when the engine is running, especially when it is running at higher rpms, so has to be properly mechanically connected to a good heat sink to control its temperature, otherwise it will fail when it overheats. Make sure the new location provides at least as good of a heat sink as the stock location.

Bottom line though, you have to narrow down whether the stall is caused by a fuel problem or a spark problem. Ask your shop to show you how to test for a good healthy spark, so you can do that when this happens.

I relocated the module because it was on the distributor, and that had been known to cause stalling (big lawsuit with Ford, in fact).

The battery cables are original, so that’d be great if that was the problem

Testing for a bad battery cable is very simple if you have a set of jumper cables. When my 87 Ranger wouldn’t crank I simply connected one end of the black jumper cable to the negative battery post and the other end to a handy bolt on the engine block. When it fired right up I knew the negative cable was toast. Etc Etc

Battery cables are pretty cheap, if it was me I’d just go ahead and replace them.

The problem is back… the mechanic had a time figuring it out, traced it to a bad connection somewhere else to the ignition module. Today it did the same thing-drove fine for a while, then died and wouldn’t restart. When turning the key, it would very very slowly crank. Some good Samaritans helped me get it off the road into a parking lot. I got a ride home and come back about 2 hours later, turned the key, and it started right up. I had AAA haul it back to the mechanic (an old Ford guy, has an 87 F-150 himself), so I’ll hopefully get it resolved. Any ideas what’s wrong? Before I. December when it did this, it wouldn’t restart for me like it did today after sitting for a couple hours. I’m really considering selling it and being done with the truck

You are definitely having an electrical problem and as stated prior you have to figure out what that is before doing anything. The alternator may be working intermittently and all the connections need to be gone through for certain.

Once you figure out the electrical problem, you will more than likely fix the issue.

If your Ford guy figures it out, please be sure to post the answer.

I certainly will. I hope it gets fixed for good, it appears to be a relatively common problem. It’s terrifying when you’re on the road and the truck dies with traffic behind and around you

I believe I have it fixed. One reason for the stalling was a bad signal from the iac valve to the CPU and the reason it outright was dying was due to a bad battery and alternator. Thank you for the input and I hope someone can learn from this