HMMWV No Start

[TryDoubleG]

I have an M998 with Nartron Smart Start Box (with diag port). No start progressively worse as it got colder.

Wait light turns on for 5 - 10 seconds then turns off. Cranks strong. Blows white smoke.

From the threads I’ve read on this forum I thought it was glow plugs so I replaced them but the problem persisted.

Brand new batteries maintained on smart charger.

Looking for some direction on next step testing/diagnostics.

Thanks in advance!


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[TryDoubleG]

Truck is equipped with Kascar grounding kit and rear block cooling kit. Otherwise stock.


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[Katavic918]

Have you verified that the glowplugs are actually glowing? Pull one out and ground it while the wait light is on.

 

[TryDoubleG]

Ok. I will try that.


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[BLK HMMWV]

Were did you get new glow plugs from ?
Are they 24 volt plugs?

 

[TryDoubleG]

Yes they are from one of the HMMWV specialty shops back east.


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[Bulldogger]

Air filter not obstructed/dirty? Any confirmation that you have compression?
BDGR

 

[TOBASH]

Yes they are from one of the HMMWV specialty shops back east.


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I have other Diesel vehicles.

My LandCruiser is 24 Volt. I used a vendor who I was told was awesome. I specifically told him 24 Volt glowplugs and he replied he understood 24 Volt. He sent 12 Volt and I needed refund and new glowplugs of appropriate Voltage.

Trust no one, and double check everything.

MHO, YMMV.

 

[TryDoubleG]

OK. I removed a glow plug and connected the threads to the grounding kit. Plug did not heat up. I reinstalled the glow plug. Then replaced air filter. No change. Sprayed one squirt of starting fluid in air filter housing. Truck started right up.

Is this enough to condemn the smart start box?


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[porkysplace]

OK. I removed a glow plug and connected the threads to the grounding kit. Plug did not heat up. I reinstalled the glow plug. Then replaced air filter. No change. Sprayed one squirt of starting fluid in air filter housing. Truck started right up.

Is this enough to condemn the smart start box?


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You might want to rethink using starting fluid , indirect injection don't like it much .

 

[TOBASH]

Smarter men have said it before me.

"NEVER USE ETHER!!!"

Check your glow plug controller.

 

[TryDoubleG]

Isn’t the smart start box the glow plug controller?


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[TOBASH]

There is an aspect of glow plug control however there is a cylindrical device that works with the smart box that also needs to be checked IIRC

 

[Katavic918]

I would check for voltage at the glow plugs first. Same as before but check for positive 24v at the plug boot. Also, FYI. Never disconnect the controller with the batteries connected. This will damage the controller.

OK. I removed a glow plug and connected the threads to the grounding kit. Plug did not heat up. I reinstalled the glow plug. Then replaced air filter. No change. Sprayed one squirt of starting fluid in air filter housing. Truck started right up.

Is this enough to condemn the smart start box?


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[Yoursmiledoc]

We have dealt with this issue extensively. Here is what we have learned. Some controllers are smart enough to not cycle the glow plugs back to back at 24 volts because they cook the plugs very easily. (experience) We spoke with a glow plug manufacturer that confirmed that they glow at 12 or 24 volts. We now modify the boxes to use 12 volts to the glow plugs and have a push button on the dash. You can push it all you want, you can push it for fun, your kids can push it, your neighbors can push it, and the mailman can push it and never blow up the glow plugs. The trucks start right up and we never worry about blowing a box/glow plugs again. We do the mod for all our trucks. If you want I can see what we would charge to mod your box......

 

[TryDoubleG]

Yoursmiledoc. Thanks for the feedback. I would be interested in the quote to mod the box.

What you’re describing is what I read on the Gear Report site as it described how the newest KDS box functions. I think.


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[Gear Report]

Here's a comprehensive look at things that could keep the HMMWV from starting.
https://gear-report.com/help-hmmwv-wont-start-humvee-glow-plug-start-system-maintenance

Sounds to me like you need to check each glow plug with an ohm meter...
If the wait light is cycling properly, then it likely isn't the start box. Could be your TSU, I suppose. Since you have a diagnostic port, your box doesn't use a Glow Plug Controller.

Yoursmiledoc. Thanks for the feedback. I would be interested in the quote to mod the box.

What you’re describing is what I read on the Gear Report site as it described how the newest KDS box functions. I think.


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[TryDoubleG]

Today when I went to move the truck out of the garage the wait light started blinking. This was the first time it has ever blinked when turned on.

Gear Report. Thanks for comments. Really like your site and all the info. A must read site after buying one of these from auction.

After all I have read I can totally understand how these boxes go bad when the trucks are left to sit for long periods with no battery tender.

My question is this. When a truck is given new batteries that are on a tender, glow plugs, grounding kit and a new Smart Start Box...how often if ever do the boxes fail?


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[Gear Report]

Today when I went to move the truck out of the garage the wait light started blinking. This was the first time it has ever blinked when turned on...

I've seen that behavior when the batteries are a little weak. Not really likely if you have new batteries that are kept on a tender, but that is when I saw blinking.

When a truck is given new batteries that are on a tender, glow plugs, grounding kit and a new Smart Start Box...how often if ever do the boxes fail?

How often? I have not data on this at all. But I'd speculate that they are like any electronics. The longer they are exposed to moisture, temp changes, voltage/current fluctuations, vibration, etc., the more likely it is that they will fail. The newer boxes are rumored to be a more robust design. I'd love to hear from an EE on this.

And thanks for the kind words.

 

[BLK HMMWV]

I guess I've just been lucky . same control box since I got it HMMWV 14 years ago.
I did swap motors from 6.2 to NA 6.5 put new plugs in when I swapped motor, not because I had to just because I wanted to know the history of them.
No new fangled anything just the way it was issued. not sure why anyone wants to change it from the original design. Seems to work just fine the way it was issued.