99 Ford Ranger

[TR21HP]

My son has a 99 Ranger with the 4.0 V8 that starts and runs really well most of the time. Occasionly it will not start. It will turn over but not fire. I've changed the plugs, wires and fuel filter but once a month it fails to start. Let it sit for a day and it turns over on the first crank.

Any ideas on what would cause this? I've brought it to a dealer and they will say we couldn't get it not to start, fired first time. Frustarted to say the least.

[Scott K]

A few things I would look at next time it happens, and it something that anyone can do. Watch what the check engine light is doing. When it doesnt start, look at the check engine light in the dash. Key on, engine off/run position see if the check engine light is on, if it is on, does it go off when cranking the engine?

This tells you, if the light comes on, that the engine computer is powering up, it doesnt tell you if it is good, just that it is powering up. If it doesnt come on, I would look to the pcm relay/engine computer relay, or powers and grounds to the computer.

If the light comes on, then goes off while cranking, that means the engine computer is getting an good rpm signal, and it is using it, and should also be using it for injector pulse, turning the fuel pump on, and ignition spark. If it comes on, and stays on, it is usually something going on with the crank shaft sensor.

Assuming there wasnt any codes, or you would have listed them? Most other things will set a code.

[TR21HP]

Thanks Scott, next time it happens I'll check it out. No codes displayed.

I'm just frustrated by the timing of this it as it can go 3 months starting every day and then it happens.

[Scott K]

I should also add, have him listen for the fuel pump when it doesnt start. See if you can hear the pump buzz/whine when you first turn the key on for a few seconds.

[nitro640]

we had a tempo that wouldn't start for the wife in the morning but would start in the afternoon when i got home, it was a relay for the fuel pump.