White smoke at start up

[Lazboytt]

Hello,
Just want to thank everyone for all their help with my questions as I am a new owner of an M998.

I was wondering if anyone else had this issue and what you did to solve it.
When I start the hummer it has white smoke at start up and I smoke out the neighbors lol. After a few minutes its gone.
I read up where its most likely unburned fuel.

Anyone experience this issue and what did you do to solve the problem?
Obviously its a diesel so you will always have a little smoke but would love to try and reduce it if I can.

 

[DatGuyC]

That much white smoke sounds like it could be coolant in the cylinders. Does it have a sweet smell?

 

[papakb]

White smoke it typical of unburnt fuel and may be a sign that you have some bad glow plugs. You can check them with a multimeter on the resistance scales. If they read around 1-2 ohms they're good, if they read high resistance or open they need to be replaced. This problem appears worse in cold weather because the cold condenses the fuel vapor faster that warm weather will. Since you say the issue goes away after the engine warms up it probably isn't coolant getting into the engine but you can confirm this with a leak down check on the cooling system. Quite a few auto parts stores have testers you can rent or borrow to do this test.

 

[Lazboytt]

Thank you for the info. Do you know how I would go about testing the glow plugs to see if they are 1-2 ohms?
I'm sure its not coolant as it would continue until all antifreeze is gone and truck over heats.

 

[NormB]

Thank you for the info. Do you know how I would go about testing the glow plugs to see if they are 1-2 ohms?
I'm sure its not coolant as it would continue until all antifreeze is gone and truck over heats.

https://smile.amazon.com/s/ref=nb_s...=aps&field-keywords=pocket+digital+multimeter

Pick one. They’re cheap enough and easy to use for voltage, resistance, continuity and other testing.

I keep one in each of my trucks, my toolbox and own a much higher quality/pricey Fluke VOM for radio-electronic/ham radio stuff.

$20 is a very good investment.

So is printing out the troubleshooting, service and parts manuals. (hint).

Enjoy the addiction.

edit:

PS. If this is a NEW (to YOU) truck, its service records uncertain (as most of them are) it might serve you well to pull the GPs and at least look at them, touch up the threads with some antiseize paste and reinstall (if they check out).

Some of the old-timers here may smirk a bit, thinking I’m leading the boy on down a rabbit hole of busted knuckles, borrowed GP pullers, injector removal, tears, language not suitable for these pages and other frustrations.

Not at all. The way it’s sounding, the plugs (then S3/TSU) need replacing anyway.

Just sayin’

 

[papakb]

Sometimes Harbor Freight has them as give aways free with other purchases if you have one near you. You don't need anything exotic for automotive work so even the cheapies will work for.

And Norm, you know no HMMWV job is complete without a blood sacrifice! LOL

BTW, S3 is the protective control box and TSU is the temperature sensor unit that goes with it. This is equipment you'll typically find in upgraded or newer trucks. In the early trucks you'll probably have a Protective Control Box (PCB) and it's matching Glow Plug Controller (GPC). These perform the same function but need to be installed as pairs. You don't want to install a newer S3 control box with a GPC and inversely you don't want a TSU with a Prestolite control box. There are plenty of postings about these units here on the SS site and online. After you find out what unit you have in your truck this will all make more sense to you. Until then it's like speaking Welsh to anyone other than another Welshman! LOL

 

[NormB]

Sometimes Harbor Freight has them as give aways free with other purchases if you have one near you. You don't need anything exotic for automotive work so even the cheapies will work for.

And Norm, you know no HMMWV job is complete without a blood sacrifice! LOL

BTW, S3 is the protective control box and TSU is the temperature sensor unit that goes with it. This is equipment you'll typically find in upgraded or newer trucks. In the early trucks you'll probably have a Protective Control Box (PCB) and it's matching Glow Plug Controller (GPC). These perform the same function but need to be installed as pairs. You don't want to install a newer S3 control box with a GPC and inversely you don't want a TSU with a Prestolite control box. There are plenty of postings about these units here on the SS site and online. After you find out what unit you have in your truck this will all make more sense to you. Until then it's like speaking Welsh to anyone other than another Welshman! LOL

Dude, if you don’t know the acronyms, you don’t know the language. Actually, it’s idioms, but we’re talking MVs here (Military Vehicles), you know?


I have Hagerty insurance coverage and the new monthly magazine had three pages of HF (Harbor Freight - heh heh) coupons. Top left hand side first page is one for a “free” digital multimeter with any purchase.

Circa 1970 my brother bought my dad a basic Texas Instruments “pocket” calculator for Christmas, thing was the size of a small paperback novel and - on sale - cost around $125. Ten years later they were “free with fill up” at chain gas stations everywhere.

 

[snowtrac nome]

It could also be the cold advance not working, a timing issue, or some marginally bad injectors. I would start with glow plugs first

 

[Lazboytt]

Hello
is this the box in question which is under the dash under the washer fluid container?

 

[frank8003]

Hey I'm just surprised that by now there is NOT a Sticky in here about glow plugs, removal tool, and electrical start systems.
The electrical diagram is available but won't upload.
View attachment HMMWV S3 HMMWV box.pdf

 

[98G]

I'm sure its not coolant as it would continue until all antifreeze is gone and truck over heats.

What makes you think so? A little coolant makes a lot of vapor...

That being said, I think what you're experiencing is normal fuel condensation on cold cylinder walls.

 

[Lazboytt]

Any recommendations on the brand of glow plugs to use? I figured I’m just going to replace them for the heck of it

 

[papakb]

There's a lot of controversy about which glow plugs are the best but I have used standard military surplus glow plugs for the last 18 years without problems. They seem to be like everything else, when your times up it's up.

 

[1 Patriot-of-many]

White smoke it typical of unburnt fuel and may be a sign that you have some bad glow plugs. You can check them with a multimeter on the resistance scales. If they read around 1-2 ohms they're good, if they read high resistance or open they need to be replaced. This problem appears worse in cold weather because the cold condenses the fuel vapor faster that warm weather will. Since you say the issue goes away after the engine warms up it probably isn't coolant getting into the engine but you can confirm this with a leak down check on the cooling system. Quite a few auto parts stores have testers you can rent or borrow to do this test.

b. Using multimeter, check glow plug
internal resistance (Figure 12-5)
Connect one test lead to terminal (1) and other
test lead to threaded area (2).
Glow plug internal resistance should be 1.5-5.0
ohms. If resistance is not 1.5-5.0 ohms, replace
glow plug.
Figure 12-4. HMMWV Glow Plug. According to the hmmwv-test diagnostics pdf, it's 1.5-5 ohms.

OP you can check the ohms in the vehicle by lead to body of the plug.

 

[tage]

Normal for a 6.2 / 6.5 diesels