From: chance wolf (chance_wolf@shaw.ca)
Date: Thu Jan 08 2004 - 09:39:54 PST
----- Original Message -----
From: "Mike" <gundocmike@okplus.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Thursday, January 08, 2004 9:04 AM
Subject: [MV] HMMWV Newbee question
> My problem is with my 86 M998. The temp here in Oklahoma the last week has
> been around 5 degree in the mornings. My HMMWV has a very difficult time
> starting. When the temp is above freezing it starts just fine. If below
> freezing I almost run the batteries dead trying to get it started. Is this
> normal? When I turn the ignition on the wait light will go out after it
> clicks 2 or 3 times, then I try to start it. Should I let it click longer,
> "maybe 5 or 6 times", before trying to turn it over? What exactly is the
> clicking noise?
> TIA,
> Mike
The 'clicking noise' is the glow plugs cycling. The 'WAIT' light should
stay on for about 8 secs or so, then click off, and then you'll hear the
system click on and off several times after that point in what's called the
"afterglow" period.
Hummers went through several different styles of glow plug controllers and
temp sensors, but chances are your 1986 uses the same style we have in the
movie fleet, and likely suffers from the same sorts of problems. The big
one is ground. If the engine isn't grounded properly with respect to the
body/neg battery terminal, all sorts of things won't work properly. You can
visually inspect the grounds or run an ohm meter between a good, clean piece
of body metal and a good, clean piece of engine metal to see what the
reading is. It should be next to nothing (i.e. - continuity). I amazed one
guy who was having problems by actually using a test light in between those
points I mentioned above, and having the thing light up. No engine ground.
Unfun.
Check the glow plugs themselves too. Use a multimeter on a low ohms range
and, with the plug off the end of the glow plug, measure from the tip to the
outer casing. If it reads open - the plug is toast. In warmish weather the
6.2s and 6.5s will start on as few as 3 or 4 working glow plugs - but when
it gets cold - no sale.
Whatever you do, don't keep turning the switch back to 'Off' and running the
glow plugs through their whole cycle again. That's called "stacking", and
cost Uncle Sam a fair chunk of change in terms of failed glow plugs when
soldiers kept doing it on the first HMMWVs.
I've had other things go bad too related to the glow plug system - chiefly
the PCB (protective control box) mounted up under the dash above your foot
pedals - but also the engine-compartment harness itself. Some of the early
PCBs like to get full of water and begin to go a bit random on you, and some
of the harnesses develop an intermittent right where they terminate at the
plug screwing into the top of the PCB. Seen two of those.
There's also a Cold Advance Solenoid and valve on the injector pump. When
the engine is cold, this valve is supposed to open and provide an
unrestricted fuel return. They stick, or there's no operating voltage at
the terminal - or the valve itself gums up sometimes, leaving you with a
hard-to-start-from-cold problem. I've yet to see one of those valves get
hopelessly gummed up on a Humvee - but the same exact style is used on the
CUCV and I've seen a fair number of those clog up almost completely. Check
all the other stuff first, as I think this is a 'out in left field'
possibility in your own case.
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