I've developed an electrical issue in my 85 F350 6.9 diesel. Someone powered an electric fuel pump off a red wire with yellow slash marks; this wire protrudes through the fire wall on the left side with the main harness. It travels in conjunction with two other wires (red with white dash and black) and terminates in an unused connector.

I have read some caveats online about powering a fuel pump directly from trigger voltage and will rewire the pump to a relay when my problem is solved. The problem is intermittant and seems to be related to movement in the gear shift or transmission linkage. When I down shift, the problem occurs or goes away.

Lack of power to the red/yellow slash wire affects the fuel shut off solenoid as well. I needed a quick fix and wired the pump directly off the battery through a manual switch but had to jumper power to the red/yellow slash wire before it would start.

When I energize the remote switch with the key switch "off", not only does the fuel pump start to run, but also the dash lights and buzzer cycle (seat belt warning and brake).

If someone has any ideas re what I am dealing with, I'd appreciate the advice. If anyone knows where I can purchase a high quality reprint of an electrical and vacuum manual please direct me there. Thanks.

 

How about the wiring diagrams?

Lloyds Auto Liturature available for 1985, Fordtruck, Wiring Diagrams

 

Thanks. They have some NOS electrical manuals which I ordered.

 

The red/yellow-hash is a key-on feed for various engine control solenoids under the hood, I don't remember anything more specific than that, sorry.

 

Hooking the Red/Yellow hash wire directly through a jumper wire will back feed the ignition switch. Why you are having the problem with the warning lights with the ignition switch off. I would check the ignition switch for a potential problem inside.

 

Thanks guys for all the info. I was beginning to wonder if I could have a problem in the ignition switch after ctubutis told me the red/yellow dash comes from the ignition. Kind of fits with the transmission linkage causing an interruption in power when I shift into low. I think you guys saved me from a lot of grief on this one.

 

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