'99 Taurus 3.0 fuel pressure problem on hot days

On a hot day, if I drive for a short time and then turn off the car, it won’t start up again. It will start back up if I let it sit for an hour or if I fill the tank (If the tank is less than half empty, the likelihood of the problem increases.) When I try to restart the car, the starter motor cranks just fine so there?s no problem with the battery.

Also, on a couple of occasions, the motor has died on the freeway and once. Once it died going through a carwash. In each instance, I had to let the car sit for an hour or I had to fill the gas tank.

This Taurus has a 16 (I think) gallon tank and if I accidentally run the tank dry, I can only put in 12-13 gallons. Likewise, if I fill the tank when the fuel light goes on I can only put in 12-13 gallons.

Obviously there is a fuel pressure problem. Is the fuel pump bad? If so, why does it fail only under certain conditions? I tripped the reset switch in the trunk but that didn?t help.

I searched this forum and some others and found some other owners who were having the same troubles.

In a post last year on this forum (Fuel system heat failure) the member had a similar problem and the consensus was not conclusive except that temp and humidity should not affect the fuel pump and that the problem lies with the ignition module. I?m not clear on how the ignition system would affect fuel pressure but?

In one case, the writer said that the fuel pump relay could fail b/c it is heat-sensitive. Another said that he had traced the problem to a bad ground for the fuel pump that causes it to fail when subjected to certain amperage. A third suggested that the wiring harness on top of the tank can get smashed against the underside of the car and overheat (i.e. his pigtail harness was cracked open at the fuel tank connector.)

BTW, my mechanic was stumped. His only suggestion was to install a new fuel pump but given what I?ve read, I?m not sure that is the sure-fire fix.

Do you have any thoughts on this problem?

If the pump is marginal it may be having problems when the tank gets lower because of a phenomenon called “head pressure”. The pump pickup tube is toward the bottom of the tank, and the weight of the gas can actually assist it in pumping.

This could have been caused by occasionally running the tank dry. That can cause premature pump failure.

I’m not “buying” the heat sensitivit relay theory. Mainly because it’s only doing its problem when the tank is llow and because it stalled while running.

That makes sense. btw, I only ran the tank dry once to see what would happen and even then I believe that there was 3 gallons still in the car b/c I put in 13 to get it full (I had 5 gallons in a gas can in the car and I put in 7 at the pump.) Weird isn’t it… but I suppose that would jibe with what you said 'bout the fuel exerting pressure on the pump if it doesn’t suck all 16 gallons out of the tank. THX

You might try spending the next couple of weeks keeping the gas tank full - keep it constantly above 3/4 tank or so. This is a little inconvenient in terms of time, but if the car exhibits no problems, then mountainbike’s idea would get supported.