I was going over my truck today to check out what I need to do to install gauges and I found a wire going from the pos post of the battery to a switch under the dash. then from the switch to the lift pump. The wire was disconnected from the switch and the wire from the battery did not have a fuse on it. I did not notice this wire when I bought the truck last month and this is my first diesel so any ideas?

 

I've never noticed it either. I'll have to check it out. If I find out I'll chime in.

Eric

 

This wire was installed by one of the previous owners.

 

Ok, I misread that. I can be dislexsic at times! lol

 

Ejection seat??

 

Sounds like someone had a problem with power supply to the fuel pump... Or they created a fuel shut-off switch... Hmmm... Hard telling...

 

When you first turn your truck to the "On" postition you hear the lift pump cycle breifly..... try fiddling with the switch while the pump runs and see if you can hear a difference.

Also, try just "bumping" the starter, just turn they key and hit the starter briefly so it it just "bumps" but doesn't start the engine. You should hear the lift pump run for longer now. Do this with fan and heater controls turned to "off" and you'll be able to hear it better. fiddle with your switch and see if it makes the lift pump turn off or on or something.

 

Maybe they used it to prime the fuel filter canister or bleed air from the lines after a filter change because they didn't know how to bump the starter and do it.

 

Thanks guys, I will try all of that and report back

 

could be a fuel shut off they used to deter an easy theft of the truck as well

 

But if it just shut the Lp off wouldn't it still run with just the VP sucking??? (like having a dead lift pump)

Probably the thief would get away far enough until the VP failed from 0 fuel pressure and you'd get your truck back with a smoked VP.

 

Wow!.......that would be a terrible way to have an anti theft switch setup! ......turn the lift pump off so it fries the VP?!?!?! ........It would disable the truck eventually I guess?!?!......

 

DOHHH!!!......I guess you type faster than me tool!!! .......If that switch is there to interupt the LP circuit you must disconnect it asap!!

 

now that i look at that i realize that its prolly a dumb way to be set-up...sorry for my lack of thinking it out before typing...

not a good theft deterrent

 

Maybe someone had an after market fuel pump mounted somewhere, and to keep it from having pressure spikes upon start up, they had this switch wired to it, so they could cut it off during starting????