2000 Ford E-150 won't start when hot after idling

This has been an on-going problem since early in 2009. It all began when my wife’s van wouldn’t start one morning. I gave it a jump start and off she went. A few days later, same thing. Ended up replacing the battery (it was 6-years old). Problem solved.

A few days later, the van would not start again. Checked the battery connections. Everything looked good. Windows, horn, locks, radio…all working just fine. I pulled the starter and took it to be tested. It was still functional but was slightly intermittent. Since it was under warranty and already pulled, I told them to give me a new one to install. I installed the starter and the van cranked right up. Problem solved!

A few days later, the van wouldn’t start. This time, it was at the kid’s school. My wife had been idling in the driveway for about 10 minutes (for A/C…it being a hot day in February here in Houston.) As school let out, she killed the engine and went inside to collect kids. Once she loaded up, the van would not start.

Let me clarify. When I say ‘not start’, I mean that nothing happens. No clicking, no cranking, no humming, no nothing. The normal lights on the dash illuminate. The radio, A/C, horn, windows, dome lights and door locks all function properly.

I drove my truck to the school and picked up the family and took them home. Later, a buddy and I drove to the school to see about towing it to the house. I got inside to see if it would start, and it fired right up! That’s right…intermittent electrical failure - my favorite! I drove the van to the house, parked it in the driveway and killed the engine. I then tried to start it again and it fired right up. Problem solved???

So, if I can’t replicate the failure, I’m going to have a hard time fixing it. I let it ride. About a week later, the same failure occured. I began asking my wife some questions regarding what she had been doing just prior to the failure. It turns out that she had been running errands, starting and stopping, turning on and turning off. I picked her up and began to think about how to tow the van to the house. When I went to do so later that evening, I tried the ignition again and it fired right up!

I think I’ve bored you with enough details for now. Let me try to wrap this up. I got the van home and luckily the next time it failed, it was at home. I picked up an ignition switch on my way home. I tried to start the van with the old switch with no luck. I put in the new switch in about 5 minutes and the van fired right up! Problem solved!!!?!?

Several days later, the van failed again. I told my wife to lift the hood to let it cool faster and I went to pick her up and take her home. After a couple hours, I drove to the van, got in, and started it right up! The failure is heat-related. To test the theory, I had my wife drive 20 miles out and 20 miles back on the freeway. She parked in the driveway, killed the engine and restarted it right away. We killed the engine and waited ten minutes. It started right up. We then left it running for 20 minutes with the A/C on. When we killed it that time, it would not re-start. I opened the hood and placed a box fan to blow air across the engine. After about an hour I tried to start the engine and it fired right up! What this taught me was that with enough air passing around the engine (freeway driving), heat was being dissipated at a high enough rate to keep the ‘gremlin’ from reappearing. However, when idling in-place, heat was able to build to a point where the failure would occur. Once cooled again, the failure mode disappeared.

Possible suspects that I’ve thought of are the Generic Electrical Module (GEM), an oil or water coolant temp sensor, or the starter relay. I don’t think it’s the GEM. I just can’t convince myself that the failure modes of a GEM could possibly translate into what I’m experiencing. Also, since it is the most expensive fix, I’m going to keep that as a last resort. Last night I did some testing with the coolant sensor. I let the engine run for 10 minutes and recreated the failure. I then cooled it with a box fan for an hour and re-started the engine and killed it imediately. My reasoning is this: The sensor is possibly failing “high”. This does not cause the engine to stop, but when trying to start, the computer chip gets ‘start/don’t start’ signals from various sensors and this failed temp sensor says ‘don’t start’. However, once cooled off, it somehow resets and says ‘start’. This is all speculation - I don’t know if the chip goes through this sort of diagnostic prior to each ignition. But, I figured that if I pulled the lead to the sensor, the chip would not get a signal and would not let the engine start. I tested my theory and the engine still fired right up. Theory failed, I think. It might still be an oil cooland sensor failure, but if the water coolant sensor does not give ‘go/no go’ signals to the ignition system, I’d be hesitant to think the oil temp sensor would.

So, now I’m down to starter relay. I’ll investigate that this afternoon.

Sorry for the long message, but I suppose the final question is this: Has anyone had a similar failure and what was the solution? What are your ideas? What’s a good troubleshooting strategy?

This is my first post to this forum and I’m really looking forward to some helpful information!


When this kind of trouble happens it is pretty common for the trouble to be with the neutral safety switch. Your vehicle has what Ford calls a digital transmission range switch instead. Try placing the shifter into neutral the next time this happens. If it starts that way then the switch may need adjustment, cleaning, or replacement. The trouble could also be with the starter motor relay but I suspect the switch may be the real cause.

Thanks. I already tried the neutral safety switch test to no avail.

It might be the starter relay. This is under the hood near the battery. So engine heat could be effecting it.


I think it’s the relay too. Might be fixable if you’re handy with a soldering iron. Google ‘relay solder joint’.