mw6886

98 4.0 with 215,000 miles on it.Iv been fixing the typical oil leaks on my engine..filter o-ring and others.Just replaced the rear main seal and put it all back together properly.Others have said rebuild or replace the oil pump while its apart.To save some money i rebuilt the pump just like i took it apart.put everything back to together and no oil pressure.I took the distributor out and turned the pump with a drill and still no pressure.I did put the pump together dry, just some oil on it when i assembled it.Is this why it wont pick up any oil?

cruiser54

It shoulda picked up oil even if put in dry.

Bustedback

How much did you actually save by rebuilding the pump? Five or ten bucks? Now you have to drop the pan and pull the pump again. But check and make sure the oil sending unit is hooked up first.

IGeeky1

Yeah, I'd be checking to make certain it truly wasn't pumping oil prior to ripping the pan back off. There really is nothing to rebuilding those so I can't imagine anything going wrong. I guess the only real possibility is the oil pickup having gotten unseated and no longer having a leakless fit.

After you did the rebuild and you ran it with a drill to fill it with oil prior to remounting, did it pickup oil and fill fine then? If so I'd replace oil pressure gauge with a mechanical to test with and try again.

ps, read carefully about putting distributor back in

PseudoSport

Is the drill turning clockwise? Did you assemble the oil bypass valve correctly? Maybe try priming the pump by removing the filter and poring oil down into the pump?

salad

Are you using the in-dash gauge to check pressure?

mw6886

I got it working.I did pull the oil pan back off and took the pump off and stuck the sump in a container of oil and cranked it with my drill.It picked up oil right away.I put everything back together and it is all working great.Now I have about 50 PSI of pressure according to the gauge..it did have about 30 before the rebuild..Thanks for all the advice.

Firestorm500

I'm glad you found the problem. But I wonder why it didn't self prime.

cruiser54

My thoughts exactly.

SeriousOffroad

Never put pump together (or install a new one) without packing it full of vasoline. It will prime instanly and not allow your bearings to run dry.

cruiser54

Don't want to start a war, but i've built numerous 4.0s with new oil pumps. Put oil in the crankcase, unplugged the CPS, cranked the engine for less than 30 seconds, had good oil pressure, plugged CPS back in, and fired it up.