Ok, here goes: on my 86 Bronco (302 AOD) it decided to just up and stop on
me. I tried bypassing the fuel inertia switch, have replaced the fuel
relay switch, the fuel pump(first thing I did), the entire fuse panel, and
the computer. I've checked the ignition module and physically checked ALL
the wiring (I removed the front dash!) I've got 1.72v all across the ECC
relay. I'm supposed to have 12v at the hot wire and 12 at the igniton when
the key is on, but got the 1.72v I've checked all the ground wires I can
find, and all other systems work fine, just nothing at the fuel pump. Any
suggestions would be greatly appreciated. Allen email@example.com
I can't be sure that you are esting voltage drops properly but your testing
indicates a some kind of power supply concern. This could be either hot
side or ground side related. Brush up on voltage drop testing and repeat the
tests. While the explanation may be confusng, vlt drops are easy to perform
and do tell a story if read correctly.
I had an identical problem on my Father-in-Law's 86 Bronco. Turns out that
one of the negative for the fuel pump is fed straight from the negative
battery terminal. It was one of those smaller leads coming from the post
clamp. Anyway, it was simply a crimp connector that wasn't tight enough and
over time had lost continuity all together.
Frankly, I found it doing a wiggle test, so I wasn't sure what exactly was
fed by that neg. I know the fuel pump relay, and therefore the fuel pump,
wouldn't energize when the connector was open, which was much of the time.
It's interesting that before I found the problem, a garage told my
father-in-law that he needed a new computer for that truck. I guess they
couldn't get any output from the computer, and therefore diagnosed the
computer as dead.
One more thing I should mention too. I had an 88 Crown Vic that would have
used a similar relay to feed the power to the fuel pump. I went so far as
to replace the fuel pump (like an idiot) and found that the new pump
wouldn't work either. Turns out the relay harness itself had an
It's funny, sort of. Most folks will keep the B+ side (the wiring and
see) spotless, but don't understand the B- (body ground) side of things. The
body\frame\engine of the vehicle is the return path to the source (battery).
an old timer explained it to me simply. The whole car is one big cable going
the battery. If the path is blocked or open, you got problems. I've never
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