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Oil pump will not prime...

2K views 8 replies 4 participants last post by  greend90SW 
#1 ·
I had to replace the front cover on my 95 d90. Everything is now back together but the oil pump refuses to prime. I have packed the inside of the pump with vaseline at least 5 times. The first two times i attempted to prime by just starting the engine up, no go. Since i did not want to run the bearings dry, i have used a 12mm deepwell socket on the pump shaft to turn the pump manually using an electric drill, again no go. Before my last attempt i rebuilt the pump with the genuine kit ordered from AB, the only thing i did not replace was the thimble-looking screen on the outer cup of the pump. The pan was dropped a second time to check the pickup to ensure it was not damaged when the pan was reinstalled after replacing the front cover. I have no designs on sending it to the stealer. Any help is greatly appreciated. TIA


DLJ
 
#2 ·
oil pump prime notes from Hans

Don,

Sounds like something is not getting the pump to engage or spin, but since you tried to turn the shaft mechanically, I am not sure what to suggest except to read over Hans' post about priming.

I need to hop right now, but I will check back in later and hope someone else has a better idea as to what is not working.
 
#3 · (Edited)
There are 2 front cover gaskets available...one for the older engines and one for the newer with the crank driven oil pumps. The blocks are the same and will support either oil pump style. If you use the newer gasket (ERR7280) in this application it will not prime or build oil pressure. I suspect that is probably your problem. I believe you need P/N ERR4936.
 
#4 ·
Rob, I had always wondered...... will it help to disconnect the upper line from the oil cooler and pour oil down into the pump? Or is that just wasting time?

I'll second Robs suggestion to check the part numbers of the gasket you got, and verify that you don't have the oil passage blocked. The wrong gasket will cover up the holes that the oil passes through in the cover, and you'll never get anything past it. If driving the pump shaft with the drill didn't get oil to start flowing, then there has to be some other issue preventing it.

I'd also consider maybe removing the sandwich plate for the oil cooler lines and just taking that out of the loop. To do that, remove the filter and then undo the big nut that the filter screwed into. Once the plate is off, just put the filter on the oil pump directly. It's close to 4 feet of oil passages that you willl be removing from the system and will make the priming process quicker. Then, once everything is ok, put the plate back on. Oh, and don't forget to also pre-fill the oil filter too.

-Hans
 
#5 ·
Thanx for the quick replies guys, Rob nailed it. AB farked up and send me the 4.0 liter front cover gasket, ERR7280. The proper gasket for the 3.9, ERR4936, is now on the way. (included p/n for future searches) It's a relief just figuring out the problem. Hans that is a great idea for removing the cooler manifold, i will definitely use that method after i get her back together this weekend. Thanx again.

DLJ
 
#6 ·
greend90SW said:
Thanx for the quick replies guys, Rob nailed it.
Just got back on-line. Glad Rob zeroed in on it and you have a solution. (Thank you , Rob. If you ever make it to San Diego I buy the beers to say thanks for all the help you provide around here.)

Good luck wiyh the new gasket and report back only when you are successful.

Cheers!

Follow-up Post:

Hans said:
...Oh, and don't forget to also pre-fill the oil filter too.
Another good point. I never used to do that for any of the vehicles I owned until you mentioned to pre-fill the oil filter. I do it every time now.
 
#7 ·
Some vehicles you just can't pre-fill the filter at all because of its orientation. On my Jeep it's almost laying flat, so you would just end up dumping oil on the ground. Short term, I don't know what difference it really makes, but as engine wear is always cumulative it can't hurt to do it if possible.

With the Defenders, and the length of the flowpath between the oil pickup and the bearings, it definitely will make a difference of a couple seconds on that first startup. I tried to time it one time I did an oil change, I think it's around 10 seconds between start-up and when the system fully pressurizes on a stock truck if you don't pre-fill. With the oil-stat and pre-filling it's under 4.

-Hans
 
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