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As title says, need help with stock 4BT wiring harness. I have a Pre-91 KSB style with sensor in water jacket. I have two connectors I need help with. In picture attached I believe the #2 connector goes to the 12v keyed on connection. What does #1 get plugged too? Any help would be appreciated!
 

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Your pic doers not show just where wire 2 goes but appears to be to the FSS which would go to the keyed source.
For wire 1 you will need to check what it attaches to but if it is the KSB then also goes to the keyed source.
Wire 2 does not look like original wiring, may have been bypassed out of that harness.
 

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Right, looks like there is another wire on the FSS, that usually goes to the temp sensor for the KSB.
Guess you need to be tracing some of that wiring.
Cheers
 

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There is more to this puzzle than just the connectors. The wire used in that setup was special. Don't know who the engineer was who thought up that crazy system but it can be a headache to work out. First off, do you have the sensor for the wax motor unit. It is mounted in a water passage on the side of the head. The OEM part number is 3915945. Also found under Case tractor part J915945. Case shows that part number discontinued but replaced by part 87608380. Hope you don't need one because Case sells that for $329.88. Ouch. That is not an easy part to find. It has been obsolete for a long time. The wiring harness is part 3918364. Cummins price for that piece is $244.78 but shows to be out of stock. There are other sources that show it in stock for a little over $200. Darn expensive piece of wiring harness. Also available from Case under part J918364 for $309.58. This part hasn't been used in applications since around 1990.
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Char,
Is that a resistor setup like on some of the later units? Should be able to reproduce that.
Cheers Steve
 

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Yes, but the resistance is in the wire itself. Like I said, this is a weird setup. The later version with the solenoid KSB has an external resistor added to the wire. For all I know, that wire make work just fine with the wax motor type. The terminals look to be the same. In the Cummins shop manual, the testing for the harness is the same for both types. Here's what the solenoid version looks like.
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Here's a link to the service manual on that system. It doesn't explain the reason for the resistor. It shows some CPL numbers do not have it. That should be loads of fun trying to replace a wiring harness that is specific to the CPL. Cold Start Timing Advance System (KSB) Pump Mounted (005-070) - Continued I've never understood the reason for that resistance. As you'll find, that head sensor for the wax motor type is horribly expensive. It was discontinued in 1988 but still used up thru 1990. You can find the same sensor without that fancy plug and a screw terminal for around $90. The other 2 connectors in the harness are just spade lug female type. The solenoid version of the KSB used an air temp sensor instead of water. The service manual doesn't show the part for it's harness for some reason. I suspect both the 4bt and 6bt use the same one for that application.
 

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There are 2 wires coming from that switch mounted in the head. One wire connects to the start/stop solenoid on the injection pump and the other to the wax motor KSB. There should be spade lug terminals on both those parts for the connection, Those wires aren't labeled since they are joined to a switch which turned power on or off. If you look at post #5 the next to last photo in that group of 4 shows the connections. The sensor in the head is actually a thermal switch which turn the power on to the KSB. When you first crank up the engine that switch is open with no power being sent to the KSB. During that time the KSB is advancing the pump timing to help the engine warm up quicker. Once engine water temp reaches 160 deg F, the switch on the head closes and directs power to the KSB. That voltage heats the wax pellet in that unit which allows it to turn off. If that type KSB isn't connected the injection pump is advanced all the time which is not recommended. A little hard to see in you photo, but it appears the wire from the switch to the pump solenoid is connected but that one hanging loose is the one to the KSB. You'll need to scrape the paint off that lug terminal to get a good connection,
 

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The oem wiring was a strange design as char1355 stated. It can be simplified to eliminate the resistor and other BS and still work just fine. I have had to do it on several swaps to get the pump out of cold advance. The simple way is to just run switched power to the wax motor on the pump. While not ideal, it will work just fine. The next best is to put an inline normally open temp switch in the circuit so at around 120 degrees power is applied to the wax motor to kick it out of cold advance. The wax motor may not last as long this way, but I have yet to have one fail after setting it up this way. Due to the lack of part availability sometimes you just have to make things work. Unless you live in a cold environment the KSB isn't really needed, it's mainly just to reduce cold start emissions (white smoke). They can pretty easily be eliminated with a different advance cover and pressure regulator.
 
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