I have searched to avoid bothering you guys, but am now confused. On cold startups it smokes excessively. Misses for a while, but once warm it runs like a champ. No issues to start it. Obviously better if it is plugged in. I checked for voltage at the KSB and there is none. Warm or cold. Tried starting it cold with the wire off and it is no different. Would like to troubleshoot the sensor. Is it the front or rear one? Should it have voltage going to it? Also, in reading some posts in my search, it stated that there should be two wires going to the KSB. I have one. Mine is a 92 like the one in the post. Not sure which member it was.

 

Rear one. Should have voltage when the key is on, switch should close below 32 degrees F in the manifold. Only one wire to solenoid on my truck and in the book.

 

My 91 service manual says that the rear one is the air tempeture switch for the KSB solenoid and the fwd one is the charge air temperture sensor for the grid heaters. From what I understand there should always be 12 volts on one side of the air tempeture switch ,when the air temperature is lower than 12 degrees Celsius then the switch is fully closed and lets the 12 volts thru to a resistor which drops the voltage down to 10 volts before it goes onto the KSB solenoid.

 

Just wanted to add that I don't think starting the truck with the KSB is a valid test unless it's really stinkin' cold. With the grid heater cycling on and off, the KSB switch may not see below 32 degrees, especially if the block heater was plugged in. I would think you'd need subzero temps to make sure a bad KSB system is the problem.

 

The morning I pulled the wire off of the KSB it was around -10 C. Not sure what that would be in F. Not plugged in. Grid heater works fine and cycles once started. I will check for voltage at the sensor and go from there. Thanks guys.

 

That would be close to 0 F, I think that's cold enough for it to be working. Cold enough that I don't want to be the guy out there with a voltmeter either.

 

Ah crap! Just reread the manual, that switch closes at 32 C, not 32 F. That's 90 F. On second thought, I guess unplugging the KSB is a pretty good test of whther or not it works - unless it's summertime.

 

The "ignition wire" goes to the fuel shut off solenoid, then a wire goes from the solenoid to the rear sensor, then from the rear sensor to the ksb. Some guys have had trouble because the wire running from the solenoid on the pump to the sensor was disconnected.

Alec

 

92extle,
The air temperature switch for the KSB solenoid is the rear one.
A simple way to check if the KSB solenoid is working after you start the truck, pull the connector of the KSB solenoid and if there is no change in engine sound then there are three possibilities.
a) the temperature is higher than 32*C or (90*F)
b) the KSB solenoid is faulty
c) no juice is getting to the solenoid

If temperature is not the problem, then I would check to make sure that juice coming from the air temperature switch and if that checks out it leaves the KSB solenoid as being faulty.

Quote from my 92 service manual
"The KSB solenoid circuit contains an air temperature switch and a 3 ohm resistor. The resistor drops the battery voltage to 10 volts. Battery voltage is supplied to the solenoid through the iginition switch."
---
Al

 

My service manual says the temperature switch is fully open at or above 16 deg C (60 deg F) and fully closed at 12 deg C (54 deg F). I wonder why other manuals say 32 deg C?

 

Anyone have a price for a KSB unit?

Thanks,
ramguy

 

gotta ask guys, what is the KSB and what does it do?

 

KSB is a German abbreviation for something, basically it gives full pump advance at all engine speeds which reduces smoke when the engine is cold. The important parts are the switch and the solenoid. The solenoid is on the drivers side of the pump, has a tube coming out of the top and a wire coming out of the back. Old trucks - not sure of what years, if I had to guess I'd say '89 and '90 - have a wax pellet like in a thermostat instead of a switch and solenoid. Same thing happens, just mechanically instead of with electrons.

 

I think it varies depending on what year the truck is. What year is your manual?

 

Does anyone have a part # for the temp switch? My local Dodge 'wizards' can't figure which one it is. Too cold to pull it lately. -42 windchill here tonight. Or can I get from a Cummins dealer? Thanks.