Headlights keep burning out & will not cold start at all

[darkostoj]

Problem 1:

I've put 3 sets of headlights in my M998 and they always keep burning out. Anybody know whats happening? These suckers are expensive and want to get it fixed!

Problem 2:

Out of nowhere this thing will absolutely not cold start at all. The wait light comes on and shuts off like it always has and it will just keep cranking and blowing a lot of white smoke out of the exhaust.

Put in new glow plugs and temp sensor...didn't make a difference.

Anybody know what to start checking to get it fixed?

Thanks!

 

[Bill Nutting]

I can’t help you with the starting problem, but once you get it running put a volt meter on the batteries. It should read just under 28 volts. My guess is the voltage regulator may be over charging the system and that might be burning up the headlamps... It’s also hard on batteries.
Sorry I can’t help with the starting issue.

 

[Humveeholic]

Have you confirmed that the glow plugs are actually lighting or have voltage going to them? I had a similar issue with cold starts being extremely hard to start. Unfortunately it ended up being the box not giving voltage to the glow plugs. While diagnosing I did find that advancing the timing helped a bit.

 

[Flyingvan911]

Check your grounds for the headlights. I have heard that bad grounds can cause headlights to burn out due to voltage issues.

 

[papakb]

Watch your voltmeter when the glow plugs are cycling and if you don't see the meter "dipping" as the plugs come on it's time to check them with a multimeter. They should read around 5 ohms and anything higher means they're on their way out and need to be changed. Remember to use some anti-seize on the threads when you put the new ones in.

The HMMWV is notorious for crappy grounds to the point a supplemental harness was developed specifically to address the problem. If you haven't installed one yet your asking for trouble. It's a simple thing to make up or relatively cheap to buy from HMMWV parts suppliers here and online. Well worth the time and effort to install and a simple search here on SS will get you everything you need to know to put one in. In places like the headlights where they mount into plastic (yeah I know) the wiring harness ground becomes even more important and those connections all need to be kept clean and tight. Two places to take a close look at would be the connections on the ground lug on the starter and the connector that attaches the hood wiring harness to the body harness down by the hood hinge. These two point really take a beating because they get splashed with everything the road can throw at them and will corrode quickly if not protected. Anti-oxidant grease will help keep them in good shape and you can get that at most hardware stores and electrical supply houses. You'll also want to take a look at the body ground point that's directly behind the heater controls. For some reason it likes to loosen up all on it's own and that one will give you major gauge headaches!

 

[Bulldogger]

Additional grounding, or a check of the grounding to the hood electrical connections is a good idea as stated, and I would add that you need to be careful with how you let the hood down. Many of us don't lower it slowly, but a good clunk of that hundred pound hood will jostle the filament in the incandescent headlights pretty hard. I burned/broke mine doing that when checking something right after running when the filaments and lamps were still hot.
I recommend LEDs as the solution. There are plenty of threads and links here with info, and prices keep coming down on aftermarket stuff. I used headlights intended for Jeeps, did have to cram them some but they work.

Bulldogger

 

[Gear Report]

For the headlights, like Bill said, check voltage. But I believe the correct voltage is at or slightly above 28v, not under 28v.

The grounding harness folks mentioned is easy to make:
https://gear-report.com/hmmwv-upgrades-make-diy-hmmwv-grounding-harness

For the starting issue, there is a lot of info in this article:
https://gear-report.com/help-hmmwv-wont-start-humvee-glow-plug-start-system-maintenance

 

[1 Patriot-of-many]

Once you figure out why the headlights are burning out, I found a nice solution instead of buying expensive military headlights. look up Octane Lighting on amazon. They sell headlights that use a normal replaceable 24V halogen bulb, you need to buy two wiring harnesses cheap and go to Eriks military surplus for the shell connectors. Then all you need to replace is the halogen bulb 24V anywhere from $7 on up when they burn out. They work great in my Humvee, of course I dropped one while installing it lol and cracked it, but I bought 3 sets to put on other vehicles. [h=1]OCTANE LIGHTING 7" 24V Halogen Military Headlight Headlamp H4 Bulbs Crystal Clear 24 Volt Pair[/h][h=1]ZYHW 2 x H4 9003 Ceramic Wire Wiring Harness Sockets for Car Headlight[/h]