So, I just built a new engine for my 2000 xj. I used a 1994 engine and did an complete rebuilt. Bored it .030 over, used new rods, pistons, crank, cam, lifters, rockers, pushrods, etc... It is a brand new engine through and through. All my clearances were checked with plastigauge and checked perfect. I used a new oil pump, but did use the original oil pickup. Before putting the engine in the truck I ran up the oil pressure with a drill by running the oil pump. I had a gauge on it and it was reading about 10 psi or so. It was working my drill pretty hard so I figured it was just low because my drill didnt have the nads to turn the pump. I got it all hooked up and hit the key this afternoon and it cranked right up, runs great. I checked my gauge, i have about 6-8 psi of oil pressure. I was getting some rocker noise so I shut it down after about a minute. I checked for leaks and whatnot, did some swearing, drank a beer. Tried it again about 20 minutes later, now I have 0 oil pressure. Any ideas? I am wondering if my oil pump crapped the bed. I don't know what else it could be.

 

You did make sure the pickup wasn't clogged up, and cleaned it up before putting it back in, right?

 

Yep. Cleaned it up real well. According to my 2000 xj FSM there is not an o ring or anything that goes between the oil pump and the pickup. Does that sound correct?

 

You sure you have all of the oil gally plugs installed? If you had the block at the machine shop, they may have removed the plugs when the hot tanked the block.

 

Yep. 2 on the side of the block. One in the back. They are all in.

 

What was causing the rocker noise? You could remove the valve cover and see if oil is coming up through the pushrod tube holes. If you really have 0 psi oil pressure you should see no oil. You did measure the oil pressure using a manual gauge, right?

 

Yes. This is a manual gauge. Screwed right into where the OP sending unit would go. The rocker noise I'm guessing is because the lifters and pushrods were not pumping up properly.

I just ran the oil pumP through the distributor hole with a drill and I got as much as 25 psi. Now I'm totally confused. I figured it would read low again. Why can I get 25 psi with a drill and 0 while running.

 

Well, I removed the oil pan this evening. What a treat that is while in the vehicle. I got all the bolts out in like 5 minutes and actually said, "this won't be bad at all". Then two hours later I finally got the pan off. For some reason they could not move the front axle like 1/4" further forward in order to drop the pan easier. What a PIA. I ended up disconnecting lower control arms, steering stabilizer, etc... I am wondering if I can use a ratchet strap to pull the whole front axle forward a little bit in order to make it a bit easier to install.

Anyway, I found something pretty interesting. I pulled the oil pump and the pickup tube was not seated all of the way into the pump. It was sticking out about 1/8" to 3/16". The little ring on the tube that is supposed to be seated right up against the pump was sticking out a little bit. I wonder if that could have led to my pump sucking air and it not sealing properly. Anyway, I will be doing a detailed comparison between the new pump and the original pump. Hopefully I find something definitive.

 

You should be using a Melling pump, stock specs.

Some people insist you should take a new oil pump apart and check for proper clearances before installing.

I don't recall ever re-installing a used pickup tube and screen. Too many risks.

 

I am beginning to agree with your statement. I bought a new one and will be using it. For 16$, why risk it. If that turns out to be whats up, I have certainly wasted more than 16$ worth of my time farting around with this whole debacle.

 

I had read on here some time ago that some oil pumps don't mate up to the block squarely, possibly due to some faulty castings. My Melling oil pump came with a pickup tube attached and it mounts with one of the bolts holding the oil pump on so it's impossible to work its way out.

Also note, when trying to remove or reinstall the oil pan (and trust me, its even harder to reinstall it) you could try dropping the axle all the way down, then raise it back up about 1/2 to 1" and you should be able to get the pan to clear without removing the front suspension.

Also, did you soak the lifters in oil (I left mine in oil overnight) or even pump them up with oil before you installed them?

What's your cold pressure? With a cold engine you oil pressure should be above 60psi, it would only drop after it's warmed up. Have you done your breakin yet (running engine at 2200 rpms for 20 minutes)... I kinda hope not, depending on how long you've run the engine so far. Are you using a breakin oil (such as Brad Penn)?

 

Isn't soak my lifters. Rookie mistake. Before i realized that I should have they were already installed. I have run the engine for about 1 minute total so I have not warmed it up at all. Cold temp is 6-8 psi.

I am using standard 5w-30 with comp cams camshaft break in additive. I am doing an autopsy on the oil pump to see what's going on. Hopefully it's something simple.

 

Well, the lifters pump up pretty quickly. I think its something else.

 

Did you ever check out your oil sending unit?

 

I removed the sending unit. I have a wet gauge screwed into the fitting. I just warranteed my oil pump so tonight I will try the new one. It has to be something simple.