Re: 2002 Explorer CRANKS but NO START troubleshooting


BobW <nimby_GIMME_SOME_SPAM@xxxxxxxxxxxxxx> wrote in message
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"Ulysses" <Ulysses@xxxxxxxx> wrote in message
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BobW <nimby_GIMME_SOME_SPAM@xxxxxxxxxxxxxx> wrote in message
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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?

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.


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

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

I would hope so.


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




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