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2002 Explorer CRANKS but NO START troubleshooting

My '02 Explorer, with 80K miles, failed to start twice now in the last week. It cranks fine but won't start. By time I got it into the dealer's hands it was running. They could not find any codes stored in the PCM.

I've replaced the fuel pump relay, but it failed even with the new relay.

The second time it failed, I'm pretty sure that I did not hear the momentary turn on of the fuel pump when the ignition was switched on, but I'm not 100% sure because I was in a noisy environment.

I've ordered the wiring diagram so I'll know exactly how the fuel pump is powered and what/where to measure.

So, I'm preparing to troubleshoot the problem. Here's what I plan to do the next time it fails to start:

1) Check for spark at one of the spark plugs. 2) Check voltage and current at the fuel pump inertial cutoff safety switch. If there's no current then I'll check the voltage on both sides of the switch to prove that the switch had not failed "open". 3) Check for voltage and current at the fuel pump fuse. 4) Check voltages at the contacts of the fuel pump relay. 5) Check the fuel pressure at the fuel rail's Schrader valve.

Does anyone have any other tips on how to troubleshoot this intermittent and annoying problem?

Thanks much.

Bob

Reply to
BobW
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Yes.....check #5 first. If recommended pressure is present, there's no need to check #2 #3 or #4.

Reply to
Hairy

If you find you have no spark:

Check the battery with a hydrometer. One or two weak cells might cause a no spark condition. Clean the battery connections.

Check the Crankshaft Position Sensor. A bad sensor or bad connection could cause a no spark condition.

This is assuming an ignition problem.

I'd also yank out the fuel pump relay and stick it back in just to be sure the connection there is good.

Reply to
Ulysses

I've just replaced the battery. It was the original (80K miles ago). It may do the trick by itself.

I've read about bad Crankshaft Position Sensors. You would think, however, that it would generate a code if it had failed, even temporarily.

The fuel pump relay has been in and out several times - both the original one and a brand new one.

Either way, at least now I'm prepared. Even if I get stuck again it will allow me to do some detailed debugging.

Thanks, Bob

Reply to
BobW

intermittent

Are you saying the problem has not reoccured since you replaced the battery? I've had two Fords that would crank and not start due to marginal batteries. Maybe it's a software bug or something. I'll bet the same engine would run with the battery disconnected if jump-started.

I would hope so.

Reply to
Ulysses

No. Since I've replaced the battery and the fuel filter, it has started every time.

It's good to hear that you've seen the crank but no start condition due to bad batteries. I've heard the same thing from another person. I wish I would have been ready to check if there was no spark or no fuel pressure, but at least now I'm prepared if it happens again.

Bob

Reply to
BobW

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