From: Alex (alex@glx.net)
Date: Mon Sep 27 2004 - 20:35:53 PDT
I'd like to thank all those who posted or emailed me with the various
possibilities of what might be wrong. There seemed to be a consensus
that the truck could have been running without the in-tank primary pump
working. Many pointed out their own experiences with this. Some of you
described the fuel system layout and suggested a logical troubleshooting
sequence. Thanks to all.
I called around to a few vendors for a new pump... all they had was new
and they were over $400. I asked about just mounting a general purpose
24volt pump in the fuel line ($65 at NAPA). (Some of you suggested that
approach if the pump were bad.) One dealer told me that the OEM pump was
a high volume pump and would tend to "circulate" more fuel via the
bypass back to the tank. This would keep things flowing better in very
cold weather. It sounded good to me so I decided to pull the pump and
check for obvious problems... I also didn't have a spare $450 laying
around.
I found a sealed motor magnetically coupled to a screened-in impeller
assembly. That assembly was connected to the top fuel fitting by a 1/2
inch length of rubber hose. I cleaned everything and disassembled as
much as I could of the impeller assembly. It seemed to be dragging a
little, but was moving freely by the time I finished. I reassembled the
unit, put it in the tank and measured the pressure at the pump. It was
at 7 psi. Right where the TM said it should be. Opened the bleeder on
the secondaries and a small flow of fuel came out. This was promising.
Cranked the motor for about 7-8 seconds and it came to life and seemed
to be running well. By this time it was past 9:30 and I wanted to end
the day on that happy note. Tomorrow, a test drive around the block and
Friday the homecoming parade!
Cheers,
Alex
-----Original Message-----
From: Military Vehicles Mailing List [mailto:mil-veh@mil-veh.org] On
Behalf Of Alex
Sent: Sunday, September 26, 2004 9:26 PM
To: Military Vehicles Mailing List
Subject: [MV] Duce won't run after fuel filters changed...
The story started a little over two weeks ago. In a fit of preventative
maintenance, I thought I should change all the fuel filters. Having only
had the truck a couple of months and having driven it less that 100
miles since I received it from the DRMO, I wanted to make sure it will
be ready for winter. Oil filters and oil changed the week before, I
thought I was up to the task. things are never as straight forward as
they first appear.
Went down to the local NAPA with all the numbers found on various places
on the net and bought the filters. Parked the truck in a nice handy
place to work on it and went to work. Guess what, the great looking
filters, both primary and secondary that came out, didn't look anything
like the cork ended filters that came out of the NAPA boxes. After
careful examination of the replacement filters, I concluded that yes,
they would fit in the canisters, but they were a far cry from the fit
and quality of what came out. (The filter hunt is a topic for another
post.) Two weeks later my new OEM filters arrived and I was looking
forward to a 30 minute task to get things going again.
Before I go much further, I'll mention two items that might have some
bearing on my current problem.
1) The truck always ran great, on those short trips I made, but tended
to start hard. It took about 3 tries of about 5-7 seconds of cranking
before it caught.
2) Whoever last replaced the primary filter put the lower cup on upside
down. This means the fuel was bypassing the element.
OK, I put everything back together (with the primary cup properly
installed) and installed 3 new filters.
Opened up the bleeder on top of the secondary filters, turned on the
switch, (dammed buzzer) and waited... and waited... and waited... and...
You get the picture. I could see the air bubble slowly move up on the
clear input side of the secondary replace by fuel but nothing ever came
out of the bleeder. I even opened the drain wing nut on the bottom of
the second filter... no fuel! Listened at the fuel tank and could hear a
whirring sound. The dammed truck ran 3 weeks ago when I turned it off!
OK I'm stumped. Can the truck run with a bad or very low output fuel
pump... is that how it was running. Did putting the primary filter
together correctly cause it to stop working? There seemed to be fuel
flowing at the primary filter input when I removed the pipe and turned
the switch on... but I didn't measure the pressure. Does anyone know how
much pressure I should have at the input of the secondary filters? How
about at the tank? Could there be something that is causing the fuel
shutoff to be not opening at the injector pump? I can see the plunger
move when the handle in the cab is pulled.
If I have to get to the tank pump... can this be done with the M35 box
in place, or do I have to drop the tank?
Any suggestions would be appreciated.
Thanks,
Alex
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