New to Me M998

[86humv]

Error

 

[86humv]

Guy came over today, and his truck has the yellow label KDS box.
When he turns switch on.....light flashes.
His TSU [ silver with a grey plastic top ] is installed .
So we unplugged it and plugged in a yellow banded TSU....Fixed....light now turns on and goes off like it should.
So....the wrong number TSU won't make the system work properly.
The TSU with a black plastic top [ Nartron ] has the same NSN and part number as the yellow band KDS TSU.

 

[streetsalvation]

Guy came over today, and his truck has the yellow label KDS box.
When he turns switch on.....light flashes.
His TSU [ silver with a grey plastic top ] is installed .
So we unplugged it and plugged in a yellow banded TSU....Fixed....light now turns on and goes off like it should.
So....the wrong number TSU won't make the system work properly.
The TSU with a black plastic top [ Nartron ] has the same NSN and part number as the yellow band KDS TSU.

Interesting. I did not have any wait light blinking issues. Just blown glow plugs shortly after replacement. After I unplugged the TSU, the wait to start light did blink fast. I am unsure about how to test the TSU and if I should "assume" which part is actually bad and causing the glow plugs to detonate?

 

[Gear Report]

Interesting. I did not have any wait light blinking issues. Just blown glow plugs shortly after replacement. After I unplugged the TSU, the wait to start light did blink fast. I am unsure about how to test the TSU and if I should "assume" which part is actually bad and causing the glow plugs to detonate?

I found a test procedure for the old GPC (checking continuity or resistance across different pins in the GPC), but it doesn't work on the new TSUs. Haven't located a way to check the TSU. I figured for $25 I'd get a new TSU (all my glow plugs were fried) just in case.
Also, I was having the fast blink wait light, which I read somewhere means a bad TSU. Just haven't found any reference to that in the TM to verify it.
I can't read all of the numbers on the pic of the TSU that was posted. I know that the yellow banded one works with the Smart Start box, as that is what I replaced mine with last week and if fixed my problem.

 

[streetsalvation]

I found a test procedure for the old GPC (checking continuity or resistance across different pins in the GPC), but it doesn't work on the new TSUs. Haven't located a way to check the TSU. I figured for $25 I'd get a new TSU (all my glow plugs were fried) just in case.
Also, I was having the fast blink wait light, which I read somewhere means a bad TSU. Just haven't found any reference to that in the TM to verify it.
I can't read all of the numbers on the pic of the TSU that was posted. I know that the yellow banded one works with the Smart Start box, as that is what I replaced mine with last week and if fixed my problem.

It may work to buy a TSU next time I buy another set of glow plugs. Yet $80 a pop, I really do not want to buy another set of glow plugs if the TSU is not the issue. On the same note, I would not like to spend the big bucks on a new S3 box if a TSU will do. So again, I do not have a blinky light issue; my glow plugs, that are non swellers, swell up and fail in a short amount of time.

If one glow plug goes, does it short the rest?

 

[Gear Report]

It may work to buy a TSU next time I buy another set of glow plugs. Yet $80 a pop, I really do not want to buy another set of glow plugs if the TSU is not the issue. On the same note, I would not like to spend the big bucks on a new S3 box if a TSU will do. So again, I do not have a blinky light issue; my glow plugs, that are non swellers, swell up and fail in a short amount of time.

If one glow plug goes, does it short the rest?

I am pretty new at this myself. However, my guess is that the glow plugs are staying on whenever the switch is on Run, instead of turning off after the engine has and is producing heat.
Maybe one of the more experience folks can explain how to safely check to see if the glow plugs are still being energized after they should be turned off. I'm thinking that would indicate either a bad temp sensor that isn't sending temp into to the S3 box so it knows it can turn off the glow plugs, or a bad S3 box.
Since I couldn't figure out how to test the TSU and it was the cheapest part in the mix, I replaced it just in case. However, I also had a spare S3 box and installed it also at the same time.

On a separate note, if I didn't already have a spare S3 box I would have been VERY tempted to wire 24v to the glow plugs via a momentary switch. That way I could manually control when and how long the glow plugs are on.

 

[Action]

the TSU doesn't tell the box to shut the plugs off when warmed up. It tells the box if the coolant is cold enough to require the plugs to energize at startup.

streetsalvation, when you start a cold engine, are you seeing the wait light for about 7 seconds and then you turn to START? Or do you flip the switch back and forth like mentioned by someone in another post?
I have a KDS smart start box and a yellow stripe KDS piece in the crossover pipe.

 

[streetsalvation]

the TSU doesn't tell the box to shut the plugs off when warmed up. It tells the box if the coolant is cold enough to require the plugs to energize at startup.

streetsalvation, when you start a cold engine, are you seeing the wait light for about 7 seconds and then you turn to START? Or do you flip the switch back and forth like mentioned by someone in another post?
I have a KDS smart start box and a yellow stripe KDS piece in the crossover pipe.

Nah, I just turn them on and wait to start, then start. I had previously, on my old plugs when I suspected they were shot, tried many methods including on-off-on-start. NOT on the current ones.

 

[Gear Report]

the TSU doesn't tell the box to shut the plugs off when warmed up. It tells the box if the coolant is cold enough to require the plugs to energize at startup.

So, that would mean that if the GPs are frying quickly and the grounds are good, then it pretty much has to be a bad S3 box... Right?