1991 W250 12V, wiring nightmare

[Mr1970fj40]

Hey all, so I just recently purchased a 1991 W250 12v (non inter-cooled). It has the worse electrical gremlins a guy could ask for. My issue with the truck is there is constant power to the dash and to the ve pump, even with the key off and also with the entire ignition switch taken out. The truck will start with the key but won’t turn off with the key since there is constant power to the pump, the plunger stays open so I have to use the kill lever.  My old man and I have tried looking for a short and don’t have any luck. Replaced the voltage regulator and alternator thinking that was the issue but still constant power to dash and pump. Anyone else encounter these problems? 

[IBMobile]

No but a simple solution would be to put the dash and VE power on two separate relays that are controlled by the ignition switch.

[Mopar1973Man]

Sound like someone needs to go over to the Download section pull up a Dodge FSM for that and look over the wiring maps. The key switch typically turns off both of those unless someone has created a new path by wiring modification. I would look under the dash first for modified wiring. 

[JAG1]

I had a D250 1992 for 25 years that had a problem melting fuseable links. It's  near the drivers hood hinge. They would melt when using the grid heaters, if I remember right I had to disconnect them. Those wires are so short coming out of a hard rubber block, I remember I had to cut open the rubber block to get enough wire to strip and replace the melted wires. This area is where I would look closely at. There are several wires all related to starting and stopping the engine right in there. You can feel the trouble because the wire insulation flakes off and is crispy, feels rough.

 

Keep us updated.

[Mr1970fj40]

Thank you, I’ll have dad take a look at that area you were saying and see if that’s the issue, I’m away from the truck for work and just trying to wrap my head around what could be the issue. 
 

will keep you guys updated, thanks again

[Tractorman]

15 hours ago, Mr1970fj40 said:

Replaced the voltage regulator and alternator thinking that was the issue

 

Don't replace anymore parts!  A simple test light (with an incandescent bulb) and a wiring diagram are your friend.  It is definitely possible that a previous owner added some additional wiring as @Mopar1973Manmentioned.

 

I would start troubleshooting by connecting a test light to the fuel pump solenoid and begin disconnecting non switched OEM power sources until the light goes out.  If it doesn't go out, then I would start looking for additional wiring from an non switched source.

 

- John

[JAG1]

4 hours ago, Mr1970fj40 said:

Thank you, I’ll have dad take a look at that area you were saying and see if that’s the issue, I’m away from the truck for work and just trying to wrap my head around what could be the issue. 
 

will keep you guys updated, thanks again

The fuseable link wires are the ones that feel soft and flexible in comparison to others in the same line or circuit. There is loom of wire coming out of the hard rubber block or connector there.

[Max Tune]

Possible to have rodent damage somewhere creating a path for electricity that shouldn't be there... 

That could be a long search that would be my last resort. 

[Mr1970fj40]

The wiring issue got fixed, there was a broken stud on the alternator that someone ‘fixed’ by connecting a jumper wire to a hot cable we fixed the stud and removed that wire and now ignition, dash, and pump works as it should. 

[Tractorman]

Good job!

 

- John