I've determined that the temperature switch on the intake that controls the flow of power to the Cold Start Solenoid (KSB) is bad.

#6 in this picture.


(ref:https://www.dieseltruckresource.com/...d.php?t=128911)

The best guess from my Dodge dealer says its a:

Coolant Temperature Switch #5174754AA but they want $70 for it. OUCH!!! Plus the fact that it goes into a intake manifold in the incoming air path and not coolant has me a bit confused also.

Well my local auto parts strore has now ordered two different ones and they were wrong both times even though they gaurenteed me it would be the right one.

But if search for that part number on this site:

http://www.chryslerpartsdirect.com/

It says its a Fuel system - Fuel induction - Diesel injection pump - Temp switch which makes more sense but since I'm on the west coast, and they are in NJ, it would probably take a week or more to get it from them.

I also called a local Cummins dealer and they couldn't find anything for me in their computers.

Anyways does anyone have a non-dealer part number for this #6 that I could get my lcoal Napa, Autozone, Kencths to order for me!

 

Just found an old cummins part number for the switch which is #3921642.

Once again using http://www.chryslerpartsdirect.com/

It says "Part number 3921642 was superceded by part number 5174754AA."

But that still doesn't get me a non-dealer part number.

 

Just called my Cummins dealer and they converted the old cummins part number and found it for me...

The current Dodge Part number is #5174754AA
The old Cummins Part number was #3921642
The new Cummins Part number is #3408645 and is $37.80!

So I guess I don't need any help - but I'm leaving this post here for the database....

 

Ksb has not worked sence I got the truck 5 years ago. Only time the truck hasn't started ,without the plug, is below -20°f . Aka -23°f
3921642 (off my part/ confirmation from Cummins)
1st supersede I5174754AAs (part from this thread)
now 4327029
available from:
Cummins (confirmed able to ship to day $57)
Ordered from
https://puredieselpower.com/dodge-products/89-93-dodge-5.9l-cummins-replacement-thermo-switch.html#/product/6028

https://www.genosgarage.com/product/thermo-switch-4327029/engine-replacement-parts-1
Called Gino's they said they didn't have access to 4327029 or 5174754AAs
will give them a call and let them know they do have it as a diffrent/ new pn 4327029.
Glad I'm not going to have to have this stupid thing manufactured.

 

You could always put it on a switch since it is only needed for the first few minutes of a cold start up. I relpaced mine about 4 years ago and it is already shot again....KSB stays on all the time now, so I am going with a switch for both the KSB and the grid heaters.

 

Installed.
Turns the KSB on at less then 90° IAT as intended . The other day I noticed that the switch is on at 40°f ambant with 10psi or less boost. Jump on the interstate KSB turns off get to cruse speed 70mph and it turns back on..... it is telling me that at 3psi the turbo is not putting enough heat into the IC for its air to be above the 90°f set point. This is going to get worce as winter is coming, I wont see above 0°f for months. It also turns off for hot starts (120-165°f) till I pull onto the road pushing air through the engine bay, and the turbo sees fresh air under 90°f . Then its on as described above.

Now may threads advised not to use the KSB as a poor mans proformance enhancer/ timing bump, because this will over pressure the IP case, blowing the front seal, making oil is very undesirable .

------
??? Should I be worried about the KSB only turning off in summer or wide open throttle (wot is the only time I see over 10psi) based on the 90° f IAT factory set point ???


---_-
KSB started leaking as a side effect of being defunct for so long ,and being brought back online. Unplugging the KSB reducing fuel loss rate . Rocky Mountain Cummins/Peterbuilt I-15 Idaho exit 113 said/showed me the only way that they can get o-rings /gaskets for the KSB is to order a complete VE at $2300 that would have to be shipped from Cummins direct.

Dream Big Chisel Down To Reality

 

I am not sure where you are leaking, however, the DGK-121 kit includes the o-rings for the KSB pressure regulating valve and the gasket between the ksb housing and the main case. Start a new thread and post a picture of the leak if you can . . .

The front seal and bushing are only exposed to supply pressure, not case pressure, so the KSB operating will not cause the front seal to be pushed out.

Further, while I have never had a case pressure guage, based on my understanding of the pump's operation, the KSB cannot raise the peak case pressure, and only effects case pressure at lower (below about 1800 rpm, if I recall) engine speeds.