new M998 owner, ignition trouble, wait light never comes on, engine won't start

[TheGreatMidwest]

I searched the forums about issue when the 'wait' light does not come on at all and engine won't start. The auction website described it as running when I purchased it, but it was another 3 months before the paperwork was processed and it was released to me. The tow truck driver and local govplant rep attempted jumping it when it was picked up but the tow driver said 'it belched out some smoke once but that was it'. Now that its been delivered to my house it won't start. It turns over well. But the 'wait' light that is supposed to show never comes on, even for a second. I left the ignition switch in that 'wait' position for 90 seconds before attempting to start it. Tried a couple of other times after turning ignition off and waiting 15 minutes between attempts. I searched the forums and found a reference to the glow plug controller or bad glow plugs, referencing a TM20 manual. I've searched this site but I'm not able to find 'TM20'. Hoping someone can help a very frustrated owner of a HMMWV.

Thanks!

 

[DatGuyC]

Sounds like you have a bad control box. Its under the dash on the drivers side near the fender. You can find replacements on ebay, the best one to get is the newer smart start system. Depending on which model is in your truck you might have to get a new temperature sensor unit that is located on the left side of the coolant crossover. Its a big cylinder with wires coming out of the top.

 

[Warthog]

Welcome to the site.

From the Technical Manuals tab at the top of the page.

http://www.steelsoldiers.com/showthread.php?78861-TM-s-for-the-M998-series

The manuals are broken down into groups for almost all military vehicles.

The -10 is the basic operators manuals, similar to a regular vehicle. Tells you the basic operations of the unit.

The -20 are the troubleshooting manuals and basic repairs.

The -34 manuals are for the rebuild of the major components.

And the -P manuals are the parts manuals with diagrams and factory part numbers.

 

[TheGreatMidwest]

Sounds like you have a bad control box. Its under the dash on the drivers side near the fender. You can find replacements on ebay, the best one to get is the newer smart start system. Depending on which model is in your truck you might have to get a new temperature sensor unit that is located on the left side of the coolant crossover. Its a big cylinder with wires coming out of the top.

Thanks! Do you have any more info on the smart start system? Is it an apples to apples swap?

 

[TheGreatMidwest]

Thank you for the breakdown! I wasn't familiar with that terminology and had no idea what the references to -20 meant. I did visit the manuals tab of this site buy couldn't locate the HMMWV version, I'll take another look.

 

[jake-cutter]

You need to make sure and contact Gov Planet and file a claim for the control box. If it was listed as running and it doesn't they should help you out, especially since the Gov Planet lot rep even noticed it wouldn't start.

 

[TheGreatMidwest]

Thank you, I hadn't thought of that, but great point. The listing is still online and says 'engine ran when jump started'. Their's the proof

 

[papakb]

http://g503.com/forums/viewtopic.php?f=63&t=230913

There's a whole lot of good information on HMMWV starting issues on this forum.

Kurt
KG6KMJ

 

[tomelroy]

this may not solve your problem, but test your glow plugs...take off the boot to each and test the resistance on each plug. One of my m998s would start in the warm weather, but once it got cold it was a no go. 3 of the 8 plugs were bad. Now it starts instantly. (my wait light was functional) Also make sure your batteries are fully charged and everything is properly grounded. If it still will not start you can start spending some money.

 

[tomelroy]

does your volt meter drop when you turn to wait? Could have a few bad glow plugs and a fried wait light....

 

[KansasBobcat]

Thanks! Do you have any more info on the smart start system? Is it an apples to apples swap?

The later boxes are backwards compatible. I just changed mine last week. Do not use a box made by Lau Industries...they have been known to start on their own and have burned-up some HMMWVs!

 

[Retiredwarhorses]

It's impsossible to state it's this or that...because at least at minimum 3 things can be wrong, 1 or all 3..
glow plugs are toast, bad TSU, bad EESS box...plugs could have been good, but bad EESS took them out, box can be fine, but the constant jumping could have toasted 1 or all 3 of above...first pull all the plugs and test them,if fine, replace the EESS and the TSU at the same time...this assumes you currently have an EESS and not a protective control box with an external glow plug controller....if you have the early PCB and GPC...replace them both with new EESS and TSU, I would also put in new glow plugs at the same time...I do this so there are all new parts in and no guess work.

do you have good batteries in the truck? If it needed jumping, they are most likely old and need fresh batteries...

 

[Retiredwarhorses]

Oh....and do not use starting fluid on this motor.

 

[TheGreatMidwest]

this may not solve your problem, but test your glow plugs...take off the boot to each and test the resistance on each plug. One of my m998s would start in the warm weather, but once it got cold it was a no go. 3 of the 8 plugs were bad. Now it starts instantly. (my wait light was functional) Also make sure your batteries are fully charged and everything is properly grounded. If it still will not start you can start spending some money.

This is great info.... but what type of tester should I be using to test the glow plugs? I'm a nube to Diesel, spent a lot of time rebuilding gas engines of all types, but not familiar with glow plugs yet so I appreciate your helpful feedback.

 

[TheGreatMidwest]

this may not solve your problem, but test your glow plugs...take off the boot to each and test the resistance on each plug. One of my m998s would start in the warm weather, but once it got cold it was a no go. 3 of the 8 plugs were bad. Now it starts instantly. (my wait light was functional) Also make sure your batteries are fully charged and everything is properly grounded. If it still will not start you can start spending some money.

Thank you, this is great stuff. Can you suggest a type of tester to purchase, and what ohm rating are you looking for on the glow plugs?

 

[TheGreatMidwest]

I checked the TM-20 document that was suggested but I can't find what the proper resistance level is for checking glow plugs, do you know the OHM value I should be looking for? Thanks again!

 

[tomelroy]

When i tested mine i used a generic multimeter. Having a clip on one lead makes it easier. 1.2 omhs if i remember correctly. Some were 1.7 and some as low as .9. The bad ones were dead (no reading) or real high.

When you turn the start switch to wait does the battery guage drop or does it stay at the same level?

 

[Mike82ndABN]

pretty sure mine were 1.8 new

dead ones didn't register a value

so tell us more about what happens when you first turn the switch to run, where is the voltage needle?, does the wait light come on? any clicking sound from under the dash? does the needle get slightly higher after a few seconds?

when you kick it over to run, does it crank, do you get a lot of white smoke? whats the air temp where you live?

I had a PCB box that was bad, kept cycling the plugs with a click sound, and would even try to engage the starter as soon as it was placed into the run position. I believe that ended up frying the glow plugs. It would still start in warm weather. You could hear the relay engaging for the glow plugs, click on, click off, click on, click off, but the voltage needle never moved (symptom of dead glow plugs). I ended up buying a modern box and new glow plugs, starts perfect now.

 

[snock]

It's probably the box if your glow plugs show continuity. You want to also check to make sure that both connectors are screwed in tightly. Usually, at least with the KDS boxes, you'll get a brief flash from the WAIT light when switching to the RUN position. The reason this happens is that the microcontroller in the box starts up with it's I/O lines in an input configuration which is just enough to switch the NPN transistor that's connected to the WAIT LED on. If it flashes like this then the box might be repairable since that at least shows that the micro is running enough to change that pin to an output and switch it low. I think a lot of the issues with these is in the alternator AC signal detection circuit but I can't say that for certain. I don't think it will allow the glow plugs to turn on if it thinks it's seeing this. I haven't mapped out the circuit yet though. If you have a replacement box you'll need either the KDS green label which doesn't need the temp. sensor or you'll need the temp. sensor which is in the crossover pipe that matches the box.

By the way, where are you in the middle of Ohio?

 

[TheGreatMidwest]

For the record, and for happy conclusion, it was a bad control box that GovPlanet replaced since the 'wait' light came on prior to GovPlanet jumping the HMMWV in order to drive it onto the trailer I sent to pick it up. They accidentally blew the controller when jumping it. For good measure, I got the a glow plug extractor and replaced all the glow plugs, most had mushroomed out. Then followed another forum's advice and made my own grounding harness for the engine. It started like a champ after making these 3 changes! Thanks everyone, hope this feedback helps a future HMMWV owner as well.