We need a little help from the experts. This a a work truck, 350 Vortec
with 236,000 miles. We've been through several fuel pumps in it's life and
when it wouldn't start this time my shop guys assumed it was another pump.
Well, it's not this time. It's blowing the ECM fuse everytime it's
installed. Without that fuse we can't even check for codes. I suspect the
PCM itself is bad. Is that the unit just behind the battery? Are these
frequent problems or is there somewhere else we should start looking for
Thanks for all tips and pointers!
Is that the unit just behind the battery?
Let me revise that statement, the unit just behind the little toolbox and
forward of the master cylinder. Is THAT the PCM? And BTW, what does VCM
Substitute the fuse with a #194 bulb in a replacement socket, the
bulb will glow when the short that's blowing the fuse is present,
have one worker watch the state of the bulb while another goes
around the truck and wiggles the wiring harnesses, when the bulb
flickers or goes out, you're near the short.
The #194 bulb acts as a load in a simple series circuit because
it's between V+ and the short to ground, keeps ya from letting
the smoke out of the wires.
Found it! The wire to the crank position sensor had gotten up against the
exhaust pipe on the passenger side of the engine and burned in two. This is
a pretty unmolested truck, I'm kinda surprised this happened to it. If you
have one you might want to check the wire routing and make sure it's not
Thanks again, aarcuda!
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