Done a little searching here and found some very valuable information to help with this 12v stuff.

Been helping a friend try to fix his 98 12v (not a 98.5). His truck wont start so I found out if I pop the hood with the key on and lift the shut off solenoid up it will start. Took the solenoid out and tested it, it test good, works in the up and down direction and not sticking. Next suspected the relay that control the solenoid, removed it and relay test good. Now I found out that the relay's coil does not have voltage when ignition is turned on. I can jump across the contacts of the relay's plug when ignition is on and the shut off solenoid will pull it self up as it should.

So is there a fuse to the relay for the shut off solenoid? It’s too darn cold and dark for a 24v owner to take a crash course on 12v fuel system problems, trying to help his buddy out.

Thanks, and any help will be appreciated

 

The infamous blue wire running to the drivers side battery!!!! Wait you state that you can jump across the relay and get power, Sounds like relay not working?? The relays do get weak. Goodluck,, Rick

 

This 98 12v does not have the "blue" wire off the driver side battery, it only has a large guage red wire that goes to the power distriburtion center.

The shut off solenoid is good, the realay is good, just don't get voltage at the relay's coil. I'm assumming that you are suppose to get voltage at the relay's coil to close the contacts on the relay when the clutch is depresseed and the key is in the start position, but we don't.

Next test down the line tomorrow evening is the brown wire comming out of the engine starter motor relay. There must be an open cirket between the engine starter motor relay output and the shut off solenoid relay's coil. Wish I had a 98 service manual, I do have a 2002 manual and its a little helpfu, just no info about the shut off solenoid stuff in a 24v manual.

 

LarryB has a 70 amp relay for that fix. www.fostertruck.com. Or Radio Shack has one also.

..PT..

 

Brain fart on year, the brown wire to starter is correct,the diagram I am looking at does not show any to the clutch,it does show a Red/Black wire coming into the relay for fuel shutdown feed, and a Red/Violet out to the solenoid. Any way I am in Choctaw Ok, if you need to see this manual and I have a factory one for a 94, Goodluck,, Rick

 

Thanks all,

Found the problem(s), using Foster Truck Accessories wiring diagram and my 2002 service manual, the brown wire going to the fuel shutoff relay's coil had an open in it that kept the relay from activating, we may have cause this by plugging and unplugging the relay, but an easy fix.

Problem # 2, now that the relay's coil is getting voltage and activating when the starter is engaged, we get voltage out of the fuel shutoff relay, but the contacts were burnt/dirty/corroded and wasn’t getting enough amps to operate the fuel shutoff solenoid.

My friend got a new relay today and said it working now.


*** Now I’m going back home to the “24 Valve Engine and Drivetrain” where I belong.