dacfan

Hi, first time poster! I've got a real mystery going on.
Background: We have owned many F150's over the years and I've never seen this before. 1988 Auto w/302 EFI. Driving along and truck shuts off. Pull over and it restarts fine. Drive it a little further and it does the same thing. It seems to happen randomly with no pattern but could be heat related. I ruled out heat because it starts right back up without waiting.

What I have done so far:
Having had this occur before I thought it had to be the pip in the distributor. I have now replaced the pickup in the distributor. The truck had a no start issue about 3 months ago and I replaced the ignition module then and it fixed that problem so the ICM is only a few months old and the truck restarts right away. When I have had ICM trouble in the past I always had to wait for it to cool off before the truck would restart.
I do not have a check engine light and there are no stored codes. Checked fuel pressure at the schraeder valve and have 40 lbs. on fuel pump prime, about 38 lbs. with engine running. Drove around yard under light load and fuel pressure maintains. Fuel pressure maintains after I cut truck off so no leakdown.I have not been able to drive at high speed under load with pressure gauge on the truck yet but because the truck shuts off so abruptly without any signs of fuel starvation I don't think that is the issue.

My guess is that a sensor is telling the ECM to kill power to the coil but with no codes I have no idea what is malfunctioning.
If anyone has continued to see this issue after replacing the pip and ignition module I would appreciate any advice.

TheCollector

check the dizzy cap and the coil, if its random it could be something simple as a bump kocking the cap slightly off and not getting spark killing the engine?

Aktech

I think it could be a wire grounding out. Just for kicks though is the truck really hot when it shuts down? Could the ect be reading the temp wrong and shut the truck down?

dacfan

I considered the temp sensor being the issue but wouldn't that throw a code? To answer the question, no it's not getting really hot. Usually shuts off after driving 2-3 miles. Sometimes that includes a trip to the barn to get hay and leaving the truck running so it would be a bit warmer. Other times it's straight out to the highway so it's not as warm when it happens.

And to AKtech, I have checked the dizzy cap, the rotor, cleaned all the connections, etc. The cap/rotor/wires are all fairly new.

TheCollector

Have you checked the battery connections? How about the ground cables? That is an uncommon issue that can cause a bad connection just long enough to kill the engine then be perfectly fine the next.

Aktech

When it is running wiggle the ignition switch.

TheCollector

Ohh good one! That is another thing to check! My moms cars ignition went to crap because she feels the need to have a good 20lbs worth of key chains on it lol the added weight can ruin the ignition and make it so you can use the back end of a spoon to turn the car on lol

dacfan

Thanks guys. The ignition switch is loose and worn out. My wiring diagram shows a red/light green wire from the ignition switch to a fusible link then a white/light blue wire to the coil and ignition module. It appears this carries 12v from the battery via the ignition switch. I guess the easiest thing to do is put a meter on the wire at the coil and take it for a drive. If I lose 12 volts when it shuts down I'll know that's the problem.
I know there are two wires plugged into the coil. One is 12volts from batt, the other is going to the tach and I don't think either one is white/light blue.

memoniz

I'm not sure about about your '88 with a 302, but on my 4.9 the coil wires go to the ignition switch and the ICM. Is your ICM mounted on the distributor? I heard Ford had problems with them overheating and that's why they put them on the firewall in a heat sink

dacfan

Mine is on the distributor. I replaced it a few months ago because the old one would quit when it got hot but this issue doesn't seem to be related to heat. With a new ignition module and a new pip in the distributor I hope I can rule those out. Maybe I'm confused by the wiring diagram. Looks to me like 12 volts is coming from the ignition switch to the coil, EEC relay and ICM and the other coil wire is going to the ICM. tach and EEC.
The diagram looks like 12 volts is at the coil from the ignition and back fed into the ICM but prior to looking at the wiring schematic I was under the impression that coil power came from the ICM.

I'll openly admit I love corvettes and own two of them but when it comes to trucks, Ford is the absolute best, period.
we've had nothing but F100's and F150's on the farm since the late 1960's
I still drive my father's rusted out '66 F100 stepside regularly but between the ghost in this '88 and changing spark plugs in my wife's '05 FX4 I'm finding it harder to keep the faith.