6.2L Wait to start light not coming on

[85 USMC M998]

Ok so I went to start the M998 tonight to fill up the tank before tomorrows trail ride. When I turned the Rotary Switch from Stop to Run I heard the "clunk" from the KDS Box but did not see the Wait to Start light come on. The Volt Meter didn't pulse indicating the glow plugs were firing. I checked the battery voltage and I have 25.4 VDC. I have the Yellow Label KDS Box (CR-2695) and Yellow Band KDS Temp Sensor (CR-2695). I got out the TM 9-2320-280-20-1 and followed the diagnostic flow chart; When I come to the point where I disconnect the connector to the KDS Sensor and turn the Rotary Switch from off to run the glow plugs cycle (Note the wait to start light flashes 14 times). On on page 2-310 step B2 it indicates to check power at pin 6 of the harness and if there is battery voltage present then there is a short in the engine connector harness. That seems strange to me; the plugs will cycle with the switch unplugged but not with it plugged in. I maybe wrong but am thinking that the KDS Temp Sensor is bad.
Your advice is much appreciated

 

[85 USMC M998]

Update - After sleeping on it I am thinking the TM was written with for the old Prestolite and Glow Plug Controller. With that said my confidence level that the issue is the Temp Sensing Unit is about 80%; however I was never one to just swap out parts. I would like to be certain before spending ~$60 on a new part to find out I was mistaken.
Anyone else run into this?

 

[Retiredwarhorses]

It's really not an option, as a mechanic for 30yrs and a Communications Engineer...all the trouble shooting in the world won't make up for doing what we called Black box change out...
many moons ago we diagnosed to the component, these days that is time consuming, that equals time and money.
So for 35.00 a new TSU can be had on eBay....Now, onto your issue.
bad news is, it most likely "85% sure" it's you KDS box...so get ready for that, and if you but a new one, get the S3 EESS.
the TSU for the yellow label is backwards compatible. I personally in 10yrs of working with the new start system, have never,seen a bad TSU, it's the box that fails. That TSU only does one thing, it sends temp info to the EESS box that says to either light, or not light the GP's.
Also....ANY WORK you do on this system requires the batteries disconnnected, or you will be buying more parts.
lastly, start pulling and checking you Glow plugs...50% of the time when the PCB or EESS tanks...it takes out 1 or more Glow plugs.

 

[85 USMC M998]

TheHummerguy,
Thanks so much for the reply. This has been really bothering me. I have some work to do.
I am still confused why would the GPs fire w/o the TSU connected; Is this a "limp home" mode? Or do I really have a bad TSU? If I am following your prior statement then if the TSU is bad the GPs will not fire so it seems that mine may be bad.
Is there any way to check the TSU?
Thanks

 

[Retiredwarhorses]

No way to test...but the signs of a bad EESS or older PCB is either a quick flash of the wait light and nothing, or a constant flashing, at the same time as you pointed out, no fluctuation of the voltage gauge showing the GP's are drawing voltage.
that is for one or both reasons...the box is fried or the GP's are fried...and of course, cuz Both are fried, GP's normally get taken out by a bad EESS. This is one reason for the supplemental ground harness.
start pulling plugs...it only takes 20-30 mins to check all of them and verify they in fact come out and can be at least visually inspected. But you have to have some parts to throw at it.
I have one or two yellow label EESS's in the shop, they both have burnt wires inside, causing various weird crap to occur...one was that it ran fine, but would not charge the batteries...found pin "can't remember" burnt in half.

 

[85 USMC M998]

Just back from the barn. All glow plugs look fine (no swelling), but I would expect that from the Kascar 007 Non-swelling plugs. Here is the Ohm check #1=2.0, #3=2.4, #5=2.5, #7=2.5, #2=2.6, #4=2.6, #6=2.2 & #8=2.0. I am not sure if they are in range or not? The TM states 1-2 Ohm but I believe that is with non-resistor plugs (which I think Kascar are not). Please correct me if I am wrong. So the question is are the plugs within spec?
Thanks

 

[Retiredwarhorses]

Those are all fine..95% of the time, you can visually see that the plug is toast.
you will need an EESS and TSU to proceed...

 

[85 USMC M998]

Those are all fine..95% of the time, you can visually see that the plug is toast.
you will need an EESS and TSU to proceed...

Thanks have the TSU ordered and will try that first. I will post the results hopefully later this week.

 

[Retiredwarhorses]

Hope it works, buy I'm sticking with bad control box...

 

[springbok]

I had the same exact issue and the TSU fixed it. You can plug it in without taking the old one out. You will know in about 30 seconds if it works.

 

[85 USMC M998]

I had the same exact issue and the TSU fixed it. You can plug it in without taking the old one out. You will know in about 30 seconds if it works.

Thanks!
yup finally got to trying the new TSU. HOTDOG it was the TSU.
I called KASCAR and they told me the 14 flashes of the wait light was a code for glow plugs or TSU. I asked if there was a list of codes that corresponded to the flashing light and they said if there was they didn't know of any. Too bad the company has the feature but doesn't release the codes.
It seems that the 14 flashes are a code for bad TSU.

I did a resistance test on the new TSU terminals and will post if anyone is Interested.

 

[Bobthebuilder]

RetiredWarHorse or anyone else...got a similar issue and just wondering if anyone has encountered a similar issue. My EESS sorta started smoking and melted a few weeks back. Had the green label so I ordered another green label (used) and hooked it back up. Wait light doesn't come on but considering its 100 degrees here...don't really need those glow plugs right now! Anyways, I figure bad box, fried glow plugs, or bad TSU. Oddly enough that's not the part that concerns me! Truck ran great prior to EESS melting. It sat in my garage a week waiting on box to come in. Now the truck suddenly won't move! I can shift between all gears but nothing! It's like it's not catching a gear if that makes any sense. This is a 89 hmmwv so there's just one wire that comes off the transmission back to wiring harness and I assume back to the EESS. Flex plate and torque converter are new. Both were broken when I got it. Fluids are good. Any thoughts from anyone?

 

[Action]

Check the fluid level in your trans.
I was reading this post and saw it is from 2015. I was going to ask the guy why he didnt try to start the humvee after seeing the light didnt come on. Maybe it was warm!
As for the green label KDS, I believe that one has a memory. As in, if you start normally and the plugs come on, then decide to stop the start, they won't come on right away. The box thinks it is warm. It doesnt use the TSU for temp.
I haven't had a green label, KDS, but I think that was the deal with those.
As for the smoking and such...are you disconnecting the batteries every time you switch these boxes? If not, you should.

 

[Bobthebuilder]

Initially when the box was smoking I had been driving it. All was fine. I went to put it in the garage and saw a small amount of smoke from under the hood. So little in fact that I thought it was just heat waves. Then I smelt the electrical burning. So I unplugged the batteries and removed it. I think I'm gonna drain the transmission and replace fluid and filter. Guess I'll order a new start box as well.

 

[Retiredwarhorses]

Is the t-case in neutral?

i frankly don't use green labels, they don't require a TSU in the water crossover, all the other EESS's do...find a yellow label or S3 EESS. TSU Won't make it smoke, at least I've never seen one do it.
check all your plugs too....

 

[1 Patriot-of-many]

Ok so I went to start the M998 tonight to fill up the tank before tomorrows trail ride. When I turned the Rotary Switch from Stop to Run I heard the "clunk" from the KDS Box but did not see the Wait to Start light come on. The Volt Meter didn't pulse indicating the glow plugs were firing. I checked the battery voltage and I have 25.4 VDC. I have the Yellow Label KDS Box (CR-2695) and Yellow Band KDS Temp Sensor (CR-2695). I got out the TM 9-2320-280-20-1 and followed the diagnostic flow chart; When I come to the point where I disconnect the connector to the KDS Sensor and turn the Rotary Switch from off to run the glow plugs cycle (Note the wait to start light flashes 14 times). On on page 2-310 step B2 it indicates to check power at pin 6 of the harness and if there is battery voltage present then there is a short in the engine connector harness. That seems strange to me; the plugs will cycle with the switch unplugged but not with it plugged in. I maybe wrong but am thinking that the KDS Temp Sensor is bad.
Your advice is much appreciated

How hot was it outside? If your coolant is above I think 70 degrees it won't come on doesn't need it.
.

 

[Action]

How hot was it outside? If your coolant is above I think 70 degrees it won't come on doesn't need it.
.

70 degrees? The heat index down hear was 108 yesterday, and my wait light came on like normal. It is the KDS Smart Start.

 

[1 Patriot-of-many]

70 degrees? The heat index down hear was 108 yesterday, and my wait light came on like normal. It is the KDS Smart Start.

I could be off as far as 70 degrees, I know when the coolant temp is a certain degrees the wait light will not come on and the GP's will not energize as they aren't needed to start.

 

[Action]

I could be off as far as 70 degrees, I know when the coolant temp is a certain degrees the wait light will not come on and the GP's will not energize as they aren't needed to start.

I know. I was wondering if the originla poster knew that. He may have started troubleshooting everything when all he had to do was turn the lever to START.

 

[85 USMC M998]

How hot was it outside? If your coolant is above I think 70 degrees it won't come on doesn't need it.
.

Been away for a while. The HMMWV was inside, I am guessing the temp was around at or below. I didn't start the HMMWV as at the time I wasn't sure if the glow plugs would turn off.