'98 Explorer starting problem

My g/f's '98 Eddie Bauer 4.0 has problems starting.

A couple of weeks ago, it wouldn't start, but the battery and everything worked fine. After a couple tries, it started right up. 2 days ago, it happened again so I replaced the fuel filter, wouldn't start until I stepped on the gas to get it going again. Worked fine until today when it wouldn't start again.

The mechanics said I should try the easy/cheap steps of getting the coils checked or fuel sensor on the fuel rail under the hood.

I hope it's not the whole fuel pump assembly.

Thanks!

Eric

Does it still start when you step on the accelerator pedal slightly? If so, I'd suspect more an Idle Air Control (IAC) servo since what it does when working properly is allow air to bypass the throttle plate to control idle speed. If opening the throttle plate allows the vehicle to start, the problem is not with the fuel system unless you have abnormally high fuel pressure.

-Rod

Does it still start when you step on the accelerator pedal slightly? If so, I'd suspect more an Idle Air Control (IAC) servo since what it does when working properly is allow air to bypass the throttle plate to control idle speed. If opening the throttle plate allows the vehicle to start, the problem is not with the fuel system unless you have abnormally high fuel pressure.

-Rod

The shop said that the fuel pressure was jumping around. Before you start it, he said it was low, and after it's started it got high.

But, it does start when the pedal is pushed to the floor board. I haven't stepped on it slightly, but I'll try that.

Pushing the throttle to the floor (Wide Open Throttle - WOT) puts the PCM in to "Clear Flood" mode and shuts off the fuel injectors. If this allows the vehicle to start that might indicate a leaky fuel injector that causes too much fuel to enter the cylinders when trying to start, and hence the low fuel pressure before trying to "Start."

-Rod

thanks rod. i just got done replacing the fuel pump assembly and it was rather easy. never done one before. the only thing that gave me a problem was the little tools to take off the tubes from the fuel lines. they were a bitch! it's doing well so far, but if the problem continues, i will follow your suggestions. thanks again!

Eric

damn, it's acting up again today after i installed a new fuel pump assembly. how do i check to see if the injectors are "leaky" like you said?

I'd start by installing the fuel pressure gauge, making sure the gauge doesn't leak, then let the vehicle idle for a bit, shut off the engine, and see if the fuel rail pressure quickly drops. If it does, I'd then pull the spark plugs one at a time and see if one has fuel on the plug, wetter than the others. If that didn't show anything, I'll use my borescope and scope the cylinders to see if there is evidence of fuel in one or two cylinders.

There are probably a few other things that could cause the pressure to drop rapidly such as a fuel leak, a faulty pressure regulator, bad vacuum to the regulator, or a faulty check valve in the pump assembly.

-Rod