What relay is used for the ops mod

[bdemutis]

Even though I cut and spliced wires when I did my Lift pump relay upgrades, I prefer Leroy's plug and ply harness. If I do another, I will either use Leroy's harness or make mine similar, by running wires down to plug into the lift pump plugs. I also do the prime feature by Tapping into the glow plugs to trigger the relay while the glow plugs are on.
Maybe we should go back to the old lift pump relay threads and mention the new and improved plug and play method. I never did like splicing into factory wiring if it could be avoided.

When doing the relay upgrade is it rarely necessary to change the OPS. Even though it is not putting out enough juice to run the lift pump, it is more than likely putting out enough juice to trigger a relay to run the lift pump.

I changed it because I was in there already. I'm confused though.
Also isn't the check engine light supposed to come on in the wait to start position or auxiliary position like a gasser or no?

 

[jrsavoie]

I used a fused wire from the battery for a power source for the relay.

See if you can find Buddy's dual lift pump relay schematic. That is what I used - but as I stated, I would no longer splice into anything. I would run the wiring the same as Leroy does on his relay upgrade with the prime feature.

You can search my posts. I posted about doing the upgrade on the 1995 Tahoe and the 1994 K3500. I believe there is a link to Buddy's schematic on both threads

If you cut the orange wire, you need to hook it back together. Or all 3 pieces back together.

I would reconnect the orange wire and source power from the battery

 

[Burning oil]

I do them this way
Pin 30 high current out to LP. (grey wire to pump)
Pin 85 low current + trigger from OPS. (grey wire from OPS)
86 ground. (BUT 86 and 85 can be ground or signal so leave yours like it is)
87 fused power from battery
87a can be hooked to + fused switched power to pun LP from under hood.

So basically switch your 87 to main power in and 30 to power to LP. Put the orange wire back together.

Problem with this mod done this way is it only saves the OPS but does nothing to help the performance or longevity of the LP, where my LP RELAY harness does.

 

[bdemutis]

I do them this way
Pin 30 high current out to LP. (grey wire to pump)
Pin 85 low current + trigger from OPS. (grey wire from OPS)
86 ground. (BUT 86 and 85 can be ground or signal so leave yours like it is)
87 fused power from battery
87a can be hooked to + fused switched power to pun LP from under hood.

So basically switch your 87 to main power in and 30 to power to LP. Put the orange wire back together.

Problem with this mod done this way is it only saves the OPS but does nothing to help the performance or longevity of the LP, where my LP RELAY harness does.

I have the orange wire hooked up it just has a jumper going to 30 I'm just going to hook everything up factory and re do it or leave it alone.

 

[Burning oil]

Just remove 30 to orange wire and hook it to where 87 is. Remove 87 and hook to bat+

 

[ak diesel driver]

The only wire you needed to cut/modify is the grey wire. Your interrupting the power to the LP and hooking up the relay between the cuts. The LP power wire becomes the signal wire for the relay.