Another possibility???
The other day I decided to install a new front wiring harness on my M35A2
due to some patches and frayed wires on the old one. I laid the new harness
out on the floor to check it over and make sure it was the right one before
I removed the old one from the truck. I noticed a couple of leads on the
new one that are not on the old one so I started to do some investigating in
the parts manuals and wiring diagrams. Turns out some trucks have a fuel
pressure switch installed electrically between the engine start switch and
the starter relay.
The switch is normally closed. Mechanically the switch is installed in the
fuel return (low pressure) line going back to the fuel tank (at the front of
the secondary and final fuel filter mount). If this switch is defective or
if there is pressure in the fuel return line, the starter will not operate.
My question is: Whats the purpose of this switch, or more to the point, what
problems might occur if there is pressure in the fuel return line? Are
these problems severe enough to warrant a starter circuit cutout switch?
Seems like pressure would build up in this line only after the engine had
started rather than before. Not much point in cutting the starter circuit
after the engine has started.
Any comments?
Ken (a sometimes confused amateur mechanic learning the hard way)
M35A2 Deuce
M151A2 Mutt
> I have looked through all the books I have, to no avail. I cannot find a
> wiring diagram to assist me in tracking the problem down. Hopefully,
> someone knows what to look at.
>
> I have a new problem: Deuce won't start. Symptoms: Turn ignition
> (?!?!) on, hear buzz, hit starter button, and nothing. While
> I'm doing this, I've had a digital voltmeter monitoring the batteries.
> Very little dip. Something like 25 volts. I even tried having
> the headlights on while trying to start it. Same result. Nice, bright
> lights, 25 volts, and no start. I suspect the solenoid. I see
> what looks like a huge solenoid on top of the starter. Wires are tight.
> I see something else, also looking like a solenoid,
> although much smaller, affixed to the engine block. There is a loose
> wire affixed to it. What is that? Thanks, gang! Jim
>
>
>
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This archive was generated by hypermail 2b29 : Tue Aug 07 2001 - 09:34:14 PDT