Won't start sometimes

I have a '98 Ford Taurus with 88,000 miles, and about 5 months ago it wouldn't start after trying several times. Then after the car sits for awhile, 30 minutes to an hour, it will start. Have taken the car to three places to have the problem check, one being Ford's, no one can find the problem. They tell me as soon as it doesn't start have it towed in and then they can find the problem. They have eliminated all the obvious choices: battery, fuel pump, etc. The problem is when it doesn't start, by the time I could get it towed to them, it would probably start. I have no idea when this is going to happen and it is so frustrating not being able to find the problem so it can be fixed. I would love to hear from anyone that has had this problem or may have some ideas.

you could always try giving the car to a mechanic and leaving it with them and having them check it every once in a while.

What are the symptoms of the no start? Does it only do it after you've been driving it recently? For instance, the car starts for you first time of the day. You drive the grocery store, spend 20 minutes in the store, and it sometimes won't start when you come out. When it doesn't start, does the engine crank, it just won't start, or does it click once and nothing else? Does it appear to be completely random, sometimes won't start after sitting over night, sometimes won't start after being recently driven, no noticeable pattern?

-Rod

It's completely random--several times after I have left work and make a stop, the car won't start. After the car sits there for awhile, I'll come back and it will start right up. It does try to turn over. Once it doesn't start and then finally restarts, I can drive the car for several weeks before it happens again.

God questions Rod. Now MarieT, has the wiring or connector to the crankshaft sensor been checked? Just a thought. If connection is not really tight, it could cause your problem.

After checking the crankshaft position (CKP) sensor wiring, if it were me, I'd grab my fuel pressure gauge and keep it in the car with me. Next time it fails to start, I'd connect the guage to the fuel rail and crank the engine over. If there's no fuel pressure, I'd check the power from the fuel pump cutoff switch (I always have a DMM with me in the trunk). Once I verified there is power from the switch, I'd start shopping around for a new fuel pump.

Condensed version:
You may have a fuel pump that, when hot, something opens up. Either brushes or windings. After it cools down a bit, the whatever is open circuit contracts and again makes contact, allowing you to start the car. While the pump is running, the breeze generated from the rotating parts keeps the problem component cool enough to continue to make contact. As it sits, powered down, the heat causes the expansion of the problem part and the car won't start.

Do you notice a problem more often when you have a low fuel level?

-Rod

The first thing that needs to be done is narrow it down to either an ignition problem or a fuel delivery problem. I would carry a timing light with me and next time it acts up I would hook the timing light up in the normal fashion and crank the engine and see if it flashes. If the timing light has a trigger you may need to tape the trigger down. shorod suggests a fuel problem, I am more inclined to think an ignition problem, possibly the crankshaft position sensor unit. But shorod's guess may well be better than mine. Bottom line you have to first figure out if the problem is FUEL related or IGNITION related.