First I'd like to say a huge THANKS for all the very helpful information I have received on this forum over the years, sometime you guys don't get to hear how much you've helped others- I just last night created an account. I'm hoping I can get some advice...

I have a 94 that the lift pump went out (I believe). However when trying to test it by jumping the relay I am not getting 12v at the lift pump. Here's where it gets interesting. Apparently there was some sort of problem where the previous owner ran 2 new wires from the junction box under the dash (directly next to where your left foot would be- or next to the parking brake) and they run straight to the lift pump. One is ground, and the other has a spade that plugs into a terminal on that junction box marked as "ORN". I did test this terminal directly and I'm not getting any power with the key off or on. I don't know what this means and where to track back from here. Anyone know what this terminal IS? and how it relates to the OPS, the fuel relay (is the fuel relay bypassed??) I have to get this figured out today so I can get to work tomorrow. Thanks guys!!

 

Mike the easiest way to jump the LP on your truck is to run a wire from a positive terminal on your battery to the G terminal on the ALDL port under the dash of the truck,try this and see what you have

 

Mayhem, thanks. This yields no results. I think because the LP is not connected to the factory wiring. I cannot figure out why they wired the LP to the junction box "ORN" terminal (the box next to the park brake). I think this bypasses the OPS and I can't find a diagram for what the "ORN" terminal is for or what is is. I think it is just a hot terminal when the ignition is on? I figure the best way to resolve all this is to just rewire the LP to a new OPS with the relay mod to 12V from the battery?

 

I'm not sure what the "ORN" terminal is Mike but it is not very safe having the LP running all the time

 

Yes the previous owner has eliminated all the factory connections to the LP with what he has done.

At this point it would be better for you to repair the original wiring and remove what he has done.

Then get a NEW AC Delco oil pressure switch and add the "OPS relay mod"(google it) or buy the kit from Kennedy Diesel.