OPS check 95 6.5L turbo

[george_01]

How do I check OPS? Had stalling ... Checked lift pump and replaced, lift pump ok now but still stalls after short period of time. Thanks in advance.

[ol9465er]

I had two OPS failures prior to four years ago, since I have installed an OPS Relay (see instructions and diagram on "Members Page") and no trouble since. The test I still do though occassionaly is start my truck when cold and let it run for a few minutes then shut it down and listen to hear if the transfer pump continues to run. It should run until the oil pressure drops. The real test of course is checking the voltage on the "power in" terminal of the OPS and then the "power out" terminal when the truck is running. If you have no power out the (but have power in) the OPS is bad. You can check at the "power in" terminal of the transfer pump also but that alone won't tell you if you do have power to the OPS switch.

[george_01]

Thanks....as we speak right now I have voltmeter hooked up to plug at lift pump. got 14 v... truck been running for 15 minutes now with no stall. I'm assuming 14 volts at lift pump while running means OPS working O.K.? gonna take it for a run and see what happens. If I get a stall under these conditions....new lift pump and ops working what would be next to check? Do OPS work ok and then fail intermittently? Thanks again, George

[ol9465er]

14V at the pump is great. I would not suspect an intermittent failure, but nothing is out of the question, it could be that the contacts in the OPS are bad and are not always making good contact. The only check to discount that would be to have VM connected while driving and monitor though this is a bit of work running a wire through the firewall.

In the long run I would change the OPS anyhow as they are cheap and add a relay as this is really the most fool-proof way of remedying this (see "Member's Area" for the instructions and diagram).

Even if the transfer pump fails though this does not mean the truck dies. The first time my OPS went and I didn't realize it the truck ran fine just smoked on hard pedal.

It sounds more like the IP or FSD is giving trouble. (I am diagnosing an IP problem at the moment also - it would be the third pump since I owned the truck, 8 years now, and fourth altogether). These pumps are notorious but I still like my old truck.

Good luck...

[george_01]

Took on test run....ran ok....if it stalls again I'll change OPS with modification...but before that I'll change FSD and see what happens....just did'nt want to spend that much money. Thanks again, and I'll update if it fails again or if it don't I'll still update.