Help! Temperature sensor, fuel pump, or injectors?

[reconnell]

RE: 94 Explorer Sport
For about the last 6 months, I have had problems with starts. When I crank the engine after it has sat approximately 10-15 minutes, after I have been running it (e.g., starting the engine after coming out from the grocery store), the engine sputters and sometimes cuts off. The engine sputters for about 1-2 minutes before the rpm's even out. No problems with cold starts or with warm starts immediately after shutting the engine off.

I noticed similar stories on this message board that were reported as temperature sensor problems. I took my Explorer in to the shop today. They said the temp. sensor checked out fine. They said it is either the fuel injectors needing to be cleaned or a problem with the fuel pump. (I have been told these are the best mechanics around this area). They recommended starting with the injectors, then moving to the fuel pump if that didn't help.

Your feedback would be appreciated!
Robert

 

[Jason_25]

Definitely not the temperature sensor.

I can't help you from my own experience but did you run a fuel pressure test? It's about 40 dollars for the gauge plus the cost of a Haynes manual. It will definitely show you if the fuel pump is bad, but not necessarily the injectors.

 

[Alec]

Servicing the injectors is a good idea, especially with an older truck. Even if it doesn't fix your problem, you'll probably get back some horses that you've lost over the years. Your situation is kinda tricky, as it only happens on a warm start, not a hot or cold start. But usually starting problems are fuel or electrical related; and injectors could definately be a cause. Good luck!

 

[Mike 92 XLT]

How to diagnose a fuel problem using a pressure gauge:

To test to see if the check valve on the fuel pump is bad: Attach the pressure gauge and let the truck sit overnight. If the pressure has bled off by morning, your check valve is bad. Doesn't sound like that is your problem since the hard starting happens when the truck is warm, not cold.

To test if the FPR is bad: Hook the gauge up. Turn the key on to pressurize the system. You should hear the fuel pump run for a few seconds. The pressure should hold at about 30 PSI. Now start the truck. The pressure should be around 35-40 PSI. If it is abnormally high, your FPR is bad.

To test if you have a leaking injector: Hook the gauge up and turn the key on. Should read about 30 PSI. If it reads low, you most likely have a leaking injector. Now, this could also signal a bad FPR, since they can get stuck open as well as closed.

Other options: Fuel pump relay. When you turn your key on, do you hear the pump running for a few seconds to pressurize the system? If not, your relay is probably bad. These are cheap to replace, like $4.

Now, one other thing. I have found that my truck starts much easier if I wait for the system to pressurize before I fire up the engine. Just wait for the fuel pump to stop running when you turn the key to "on" before you start it.

Mike

 

[reconnell]

Thanks for the advice. I'll let you know what happens.