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Diesel won't shut off

To: <shop-talk@autox.team.net>
Subject: Diesel won't shut off
From: "Keith Kaplan" <keithka@microsoft.com>
Date: Mon, 20 May 2002 10:57:07 -0700
Here's another question for all you diesel experts:

Isuzu NPR 3.8l turbo diesel cab over moving truck, 140k+ miles, 2 years
of reliable service for me.  Even in the dead of winter, between racing
seasons when it only gets driven once a month, it always starts right
up, thanks to two giant batteries.

Maybe 6 weeks ago, I parked it on a funny slope for a few weeks.
When I went to start it, I could tell it was cranking slower than
normal, and didn't start.  About 5 minutes with my 110v battery
charger/jump starter and it started right up.  I did a few errands,
shutting off and restarting the engine, no problems.  Then I parked it
for almost a month, and tried to start it again yesterday.

Same slow cranking, so I put the same charger on, but this time it still
didn't start.  Left the charger on for a few hours, still no start.
Lifted the cab to look for any obvious dangling wires/hoses, didn't see
anything.  Pulled out the air filter, and maybe a cup or two of water
ran out.  (It's an ordinary paper element, not an oilbath style.  The
air intake snorkel cap looks good to me, but we sure do get our share of
rain out here.)

Lowered the cab, left the air filter out completely, sucker started
right up.  Put the air filter back in, unhooked the charger, drove
around the block.  It ran great, but when I pulled the key out, the
engine kept running.  When I turn the key from off to on, the dash
lights come on, indicating the key switch is still working.  I had to
pull a fuel line off between the tank and the water trap/filter to get
the engine to stop.

It can't be a coincidence that it wouldn't start, and then wouldn't
stop, since it's never had either problem before.  Could there be some
kind of fuel valve that was stuck shut at first, then stuck open?  How
is a diesel engine supposed to shut off?  All the standard ways of
stopping a gas engine involve parts that aren't on a diesel.  The wiring
is pretty well routed and zip tied so I don't think anything could get
pinched by rasing/lowering the cab.

For some odd reason, there's no Isuzu NPR enthusiasts mailing list, so I
have to ask here.  I think I know my way around a gas engine just fine,
but all I know about diesels is to put that other kind of fuel in there,
and that they sound and smell funny.

keithka

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