I have been fighting this 6.5 for awhile now. List of what I have done, new lift pump, pmd, air and fuel filter. It is acting like the lift pump is not working. Studdering at low rpm w/ light blue smoke when missing. At highway speeds it is good. Could this be a OPS problem and if so were is it at on my 98 1/2 ton 4X4?


Thank you

Could be. OPS is behind/underneath fuel filter. Search forums for "OPS". You'll find everything you need to know.

OPS can wear it's contacts and cause the lift pump to pump slow or not at all. Opening the bleeder while the truck is running gives an indication of how much pressure is on the filterhousing at idle, second best to having an inline fuel pressure guage.

You could also be having a problem with you vacuum controlled wastegate. Do a search on wastegate in this forum. There have been a lot of strings written about faulty vacuum/wastegate.


By the way, if it does turn out to be the vacuum controlled wastegate, you might want to consider removing the whole poorly designed system and replacing with this:


http://www.heathdiesel.com/?action=prodinfo&partid=HDP1243You will need to remove the vacuum pump, and buy a shorter serpentine belt as well. All in all though, I think it is definitely a worthwhile investment.

The easiest way to check if it is the OPS is to attach a wire to the gray wire coming up from the OPS, this is the wire that supplies power to the pump, and bring it into the truck and attack an LED lamp to it and ground the other side of the lamp. Use an LED because the OPS is already under rated. If while driving the lamp flickers your OPS is intermittent. The OPS should make at oil pressures above 4 lbs but bad contacts may cause the lamp to flicker and stop the pump.


Take a look at my site for a mode to improve the OPS life.

'98 model, his OPS is most likely tucked under the intake manifold in front of the filter base.

http://www.heathdiesel.com/?action=prodinfo&partid=HDP1246


this is the turbomaster you will need for a 98


are you sure it is blue smoke? that might not be a good thing.Edited by: steiner43511

Thanks for the great information. The wg vac pressure is 20. I'm thinking its the ops or IP. I'm guessing the intake is going to have to come off to get to the ops? Could I measure the voltage w/ a voltage meter?

I know they made it harder to get the 96+ OPS off and on but you shouldn't have to remove the intake.

Good deal. I am going to get after it once I get my shop in three weeks. I will limp it till then. Thanks again.

It helps to have one of those $10 OPS wrences but I've seen vice grips do the job when the OPS socket wouldn't fit because of clearence.

OPS wrench? Is a local napa, carquest goign to carry one. I was thinking of a "big" socket would work. About what size is it?

Any autoparts should have it. It is a special shape, socket won't work as well if at all, size is about 26-28mm.