Working on my 92 to be daily driver.
No 12v to fuel shutoff solenoid.
I read the sticky and looked at the wiring diagram for 1991.5
I don't see a shutoff solenoid, but I do see 2 spades on a something called a fuel pump on one of the diesel engine wiring pages.
Is this "fuel pump" the shutoff solenoid?
My wires are so discolored I can't tell which one is blue and which one is black.
Cheers and thanks
Jim

 

Yes, that's the shutoff solenoid on the injection pump. (lower left on the above said diagram.

Low on the back of the injection pump should be a terminal with 2 blades on it. One is supplied 12 volts from the ignition switch, and the other feeds 12 v to the KSB circuit. That's the fuel shutoff solenoid. Both wires should be dark blue. If one is black (ground), it took out a fusible link.

 

On the fss on my pump there is a dark blue and a black. The black wire on mine goes to the ksb. So, ther're both supposed to be blue?

 

Color doesn't really matter for operation. Black would have been replaced.

I think the early (wax motor) KSBs were wired directly to that terminal. The later (solenoid) KSBs went through a thermal switch on the head just behind the IP, and from there to the KSB.

If you have 12V on the fss, it should go. Possibly fss, or something else in the fuel pump is bad, or air in the lines.

If no 12V, then you've lost either a fusible link or the ignition switch.

 

Thanks j martin and 1992firstgen1 fan
I'll be able to follow the wiring in the truck from the diagram. I spent a good hour looking for the fss - didn't realize the that was called a fuel pump on the wiring diagram.
Question if the air temp sensor activates because of the cold, will I see 12v to the KSB solenoid?
No air in lines, just installed rebuilt injectors and ve pump. A jumper wire from batt to the fss and she starts on the first turn. SO I need to find out why no 12V to FSS
Cheers

 

The power to it comes from the A21 splice, powered by the ignition switch and only protected by a fusible link. Same circuit goes to the OD solenoid, and the grid heater solenoids, and the PCM, and......well, there's lots of places for it to get shorted to ground.

 

Thanks j martin
Got it start. Got 12 V after I cut and added a new connector. The other wire I traced back to the KSB. I measured the value of the resistor at 3.6 ohms. Don't know if that is correct and don't know if the air temp sensor is working. Will read the FSM.
I forgot to measure the voltage at the KSB. I'll do that tomorrow
Cheers