Why do my OPS's keep failing

[coalminer]

Has anyone had problems with there OPS. I think I have changed mine at least 3 times in the last three years and now it seems to be failing again. I still have oil pressure on the gauge but the lift pump won't work. It is the same every time. The truck still runs and starts good but stutters a lot if your lead foot is on the throttle. Anyone else have this problem and figure out what is causing it.

[More Power]

Some theorize that repeated oil pressure switch failures could be due to an engine having a hot idle oil pressure very close the set point of the oil pressure switch. This produces constant on/off action of the switch contacts while the engine is idling, and which then hastens deterioration of the switch contacts.

A while back one member visited a local GM parts counter with a pressure testing device and a multimeter. He found a fairly broad range of activation pressures for the switches he tested. He chose one having the lowest activation pressure to install on his engine.

MP

[cudaaa]

Try replacing ops and wiring in a heavy duty relay to supply the pump with power. Hope this helps. cudaaa

[tom.mcinerney]

I'm in agreement with above posts; 3 points:

1.) I installed a relay between my OPS and the LP. John Kennedy [http://www.kennedydiesel.com/] is soon to market a solidstate relay kit that will work on the lift pump circuit, and be a real improvement.

Iff as MorePower suggests above, the OPS cycles excessively, it'll burn itself out. It'll probably also screw up the power transistors in the Lift Pump, partly from arcing in circuit, partly because the burnt OPS points present so much rsistance that the LP doesn't get enough power to run within its design limits.

2.) If you find you're replacing OPSs, do the LP too .

3.) If you're still running the original ignition switch, consider renewing it as well--the points in it fry after time too.

[jimcreek]

on mine the same problem. I after the thrird time I decieded to change fuel pump after close inspection I found a wire that had rubbed next to cross member.
I changed the pump anyway with high mileage no problem yet (3 months knock knock on wood).
I dont know if it was the bare wire or old pump or both.

[Big Red Suburban]

More Power - do you recall what the setpoint of the OPS is supposed to be or generally around? Is it like 20 psi?

Thanks

[More Power]

I haven't seen a GM spec for the set point, but the average seems to be about 7 psi. The fellow I mentioned above saw activation pressures of 5 to 12 psi in the OPS units he tested.

MP