From: Julian Burke (julian@knology.net)
Date: Thu Aug 21 2003 - 19:34:24 PDT
OK folks,
I see a need here to explain the starting system in the older Humvee
998 series and here is some scoop of the control boxes that are used in the
older HUMVEE series. This should help some folks here. I have discussed
this recurring problem with AMG, Wellman and KDS system engineers at length
over the years and all agreed that this early control box is a piece of
junk. The problem lies with the gov't specs and it took Uncle Sam over 17
years to realize that this is getting to be an expensive ongoing problem
that had to be fixed.
Glow plugs are pretty much glow plugs whoever manufactures them.
Wellman of Shelbyville, Ind. manufactured most or all of CUCV and Hummer
series glowplugs for the gov't. Their engineer there explained many things
to me which was very useful in finding problems. You see, there are NOT
really "12 volt" or "24 volt" glow plugs. A plug is rated at say 12 volts
for 20 seconds to reach a temperature of about 1700 degrees. This plug can
be left on for all day and will remain at 1700 degrees with NO harm to it or
will "swell" out. This is what they're supposed to do. 1700 degrees is a
good temperature to get the engine to start. Now when you put 24 volts to
the same plug, it will reach temperature in about 4 seconds which is how
they do the "quick start" system. HOWEVER, if you leave 24 volts on it, IT
WILL MELT or "swell" as most people say and will burn out after deformation.
Now we get into the sorry controller that the gov't specs called for.
In the old system if your engine didn't start, you would naturally turn
the switch off and repeat the same process. Trouble here is that you would
create a condition known as "STACKING'. You would be lighting the plugs
again and if you repeated this several times, you would melt the plugs. The
original controller box would NOT recognize this condition and would ruin
the glowplugs! Then things went from bad to worse! The next generation
controller had a propensity to catch the wiring harness ON FIRE or try to
start the system by itself when no one was around. This box had the extra
glowplug wiring harness that had to be installed. When Uncle Sam discovered
this, all existing units were scrapped through the DRMO. Here is one
instance where all of them should have been destroyed. (Like they normally
do but noooo in this instance!) I have seen a few of these turn up on EBAY
and either they don't know or don't care when selling them. Funny thing
that when I would email the selling party about their control box they would
ignore me or tell me to mind my own business. That's all right though, I
sent all prospective bidders the website so THEY would know. A few years
back AMG lost about 6 brand new military only Humvees in the factory parking
lot due to this condition. One spontaniously caught on fire and
damaged/destroyed others around it. They never really said much about the
incident but they knew.
ALL/MOST later and older units used a "glow plug controller" which
was/is a temperature sensor in the upper water manifold on the right side of
the engine. Its' problem(s) is that it has some electronics encapsulated
inside it and because of the extreme temperature changes, would have a
premature failure rate. It was a common problem and the most obvious one
was when turning the switch to "ON", the "WAIT" light would NOT come on
along with the glow plugs as well. You can take a new one and plug the
harness into it (without removing the old one just to check) and see if the
problem is corrected. Easy fix too.
Kascar has a replacement controller (for about $600) with box and a set
of very expensive plugs that are not supposed to swell in this application.
Bear in mind though that ALL glowplugs will swell if enough voltage is
applied to them and left on. Kascar had a re-engineered box and it supplied
a different voltage to the plugs or would not stack. This is one way to go
but their box is already obsolete! KDS systems (electronic manufacturer
that makes pretty much all of these boxes) has a new, improved box part
number CR 2699 that eliminates the need for a sensor in the water manifold!
The sensor is inside the box itself and it like Kascar's has a sensing unit
inside that prevents the condition known as stacking. If you can find one
of these CR2699's, it will prevent many of the earlier problems and failure
rates for a lower price. Also it is a direct retrofit and you just ignore
the plug to the old controller and insert a plug into the water manifold
1/2" pipe thread hole. I hope this answers some questions and helps folks
out there. If you have a question and I cannot answer it, I know who to
ask! Thanks for reading this, sincerely, Julian Burke
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