There are two wires that go to the lift pump plug. This is the one under the truck. Which one is the power wire?

There are two wires that go to the lift pump plug. This is the one under the truck. Which one is the power wire?
on my truck it is the grey wire that is the power wire. orange wire to the OPS is hot at all times and then the grey wire is hot when oil pressure is sent to the OPS.

Your truck is an OBDI is it not? Mine is OBDII. Is the lift pump wiring the same on both trucks? I'm not sure. I am installing a second lift pump for my VO conversion. I want to interupt the power wire going to the stock lift pump & reroute that to a relay & then back to the stock lift pump. My VO lift pump will be wired to the relay as well so when I am running on diesel the VO pump will not run & visa versa when I am running on VO.

Your truck is an OBDI is it not? Mine is OBDII. Is the lift pump wiring the same on both trucks? I'm not sure. I am installing a second lift pump for my VO conversion. I want to interupt the power wire going to the stock lift pump & reroute that to a relay & then back to the stock lift pump. My VO lift pump will be wired to the relay as well so when I am running on diesel the VO pump will not run & visa versa when I am running on VO.
What you can do is turn your key to the on position and read out the wire to see which one is getting power. If you have an orange and grey wire, then it should be the same. The third wire in the bundle is for your oil pressure guage in the dash. Read this thread, it should help you out.http://www.dieselplace.com/forum/showthread.php?t=268296&highlight=lift+pump+wiring+diagram

I don't have a thrid wire. There is only 2. Thanks for the link to the thread. I have already read that. The wires I am referring to are down under the truck where the lift pump plugs into the wiring harness not under the hood. I will check for power with my multimeter tommorow. I was just hoping I find out which wire on here so I would not have to be under the truck as long.

Schematic I have shows Gray wire is feed - Black with a White tracer to ground.

Mine is grey.

Schematic I have shows Gray wire is feed - Black with a White tracer to ground.

I looked at the schematic from the site that you sent me & it shows the gray wire as power. I posted the same question on a VO site & the response I got was the orange wire is the power wire. Can you use either or does the guy on the ohter site have it wrong?

Well..... There are only 2 wires at the lift pump - What colors are they?

I will double check in the morning but if I remember correctly there is a orange & a grey. Isn't that terrible I was just looking at them just yesterday & now I can'r remember for sure. I must be getting old.

Got another response from the guy on the other site. He is now not sure because he has done away with his stock lift pump & mounted another in the engine bay & got power from another source. His power wire is now pink!! Guess I have to disregard his info.

I believe the preponderance of evidence is in favour of the grey wire .

I'm thinking it is the grey wire.lol

Thanks so much everyone.

All you have to do is pull the plug off of the OPS, locate the hot wire, jump from the hot side to the other terminals until you hear the LP run: then see what color that wire is. I think that it is grey.