High Volume oil pump or stock?

[UNL1MTD]

I'm going to be doing the RMS on the MJ and I'm thinking that it would be prudent to change out the 180k oil pump while its all apart. I'm trying to figure out if the High Volume oil pump is 'safe' to put in. I guess what I'm wondering is if the stock oil pump has kept up for all these miles is there even a reason to 'upgrade.' Anyways these are the two I'm choosing between. The high volume really does seem like a deal coming with a new screen and tube and at only 50 cents more. I feel like this is a no-brainer, but for some reason I am hesitant. Any chance the high volume pump will cause any other problems on the Renix motor?

 

Stock

http://shop.advanceautoparts.com/webapp ... 6998008___

High Volume

http://shop.advanceautoparts.com/webapp ... 7002325___

 

All that said, I swapped in a full gauge cluster awhile ago and I've never had a reading from the oil pressure gauge. I did swap the sender out for the appropriate one, so I really feel like its the gauge and not the pump. The gauge just reads 2-5 psi during the entire time the vehicle is operating and the jeep does just fine, thats why I feel its just the gauge or possibly the brand new sender.

 

Thanks,

 

Sean

[HOrnbrod]

All that said, I swapped in a full gauge cluster awhile ago and I've never had a reading from the oil pressure gauge. I did swap the sender out for the appropriate one, so I really feel like its the gauge and not the pump. The gauge just reads 2-5 psi during the entire time the vehicle is operating and the jeep does just fine, thats why I feel its just the gauge or possibly the brand new sender.

 

Thanks, Sean

 

The oil pressure gauge and sender are easy enough to check. Turn IGN switch to RUN, disconnect the wire from the sender and measure the voltage at the wire connector. It should read approx. 7.5 VDC. If not, you have an open circuit from the gauge cluster. If the voltage is okay, the sender is bad. :cheers:

[UNL1MTD]

I went out and got a mechanical gauge last night and hooked it up this morning. The pressure seems to be normal. It starts off around 55, then drops to 20, then as you get on the throttle it will do as high as 50 (or atleast that is as high as I reved it). So I'm pretty sure the oil pump and oil pressure are fine.

 

Is it really worth swapping the oil pump out after doing this test with the mechanical gauge?

[aemsee]

If it were mine and I wasn't doing anything else but the RMS, I would not change it.

[Automan2164]

I would just do it anyway. You'll be right there, and its only $75.

 

Rob L.

[jimoshel]

:agree: Your there. change it. Also to get a 30PSI swing you've got bearing clearance problems. Depends on how you drive whether to worry about it or not. For the time and trouble I'd at least drop and check the rods. And to answer your question stock should be adequate. When you get engines that consistantly exceed 200-250K then it's hard to knock factory components.

[comanche09]

:agree: Your there. change it. Also to get a 30PSI swing you've got bearing clearance problems. Depends on how you drive whether to worry about it or not. For the time and trouble I'd at least drop and check the rods. And to answer your question stock should be adequate. When you get engines that consistantly exceed 200-250K then it's hard to knock factory components.

 

My 4.0L cold start idle and under load reads 62 PSI. At hot idle it reads 22 PSI.

 

This is with a mechanical oil pressure gauge T'd in with the factory gauge. The factory gauge always reads about 10 PSI higher.

 

How should I drive if I apparently have bearing clearance issues? Thanks

[89mjpioneer]

This is my oil pressure on the highway.

I drive it all the time. I just ignore the knock on start up.

[jimoshel]

We're discussing 2 conditions here which shouldn't be confused with each other. When a engine is first started the oil is cold and thick. It will read high on the guage. As it warms up it thins out, reducing the reading. Depending on conditions the difference can be anywhere from 10-20PSI to 1-2PSI, unreadable on the average guage. The other condition is when the engine has reached it's operating temp. In a perfect motor the the PSI will remain the same from a idle to 5K RPM. Not many motors are perfect. The average engine will show a 2-10PSI swing. A motor with loose clearances can show as much as 20-30PSI change. In order of wear the cam bearings are least, main bearings next and rod bearings showing most. There are exceptions but geeez, be reasonable. The loose bearing gets most of the oil and the tight bearing gets less. Drag race from the stop light, hi revs before shifting, or just plain high milage And bingo, the tight rod goes thru the block, and or pan.

[comanche09]

We're discussing 2 conditions here which shouldn't be confused with each other. When a engine is first started the oil is cold and thick. It will read high on the guage. As it warms up it thins out, reducing the reading. Depending on conditions the difference can be anywhere from 10-20PSI to 1-2PSI, unreadable on the average guage. The other condition is when the engine has reached it's operating temp. In a perfect motor the the PSI will remain the same from a idle to 5K RPM. Not many motors are perfect. The average engine will show a 2-10PSI swing. A motor with loose clearances can show as much as 20-30PSI change. In order of wear the cam bearings are least, main bearings next and rod bearings showing most. There are exceptions but geeez, be reasonable. The loose bearing gets most of the oil and the tight bearing gets less. Drag race from the stop light, hi revs before shifting, or just plain high milage And bingo, the tight rod goes thru the block, and or pan.

 

Jimoshel, thank for the explanation. To the OP, sorry about the thread hijack :cheers:

 

Under load (hot or cold) or at cold idle, my oil pressure is around 62 PSI on my mechanical gauge. At hot idle it is around 24 PSI.

 

So my Rod and Main bearings are in need of replacement? Will I have to determine the clearances on each rod/main bearing and buy the correct bearing (with respect to clearance) for each? Thanks for your help. :cheers:

[UNL1MTD]

Is there anything tricky in terms of installing the pickup tub onto the new oil pump? I saw some places recommend a specific tool and others refer to a specific sealant.

[jimoshel]

One trick we used to use but I haven't heard about lately is to drop the oil pan. Gain access to the oil gallery, usually by removing one of the block plugs or even the oil pressure sending unit. Get a sealed container like the ones used to bleed brakes with. Fill it with oil, wt not really important. Connect a hose from the container to the oil gallery. Apply 39PSI, more or less, to the container. Look at the bearings and see where the oil is flowing from. A loose bearing, or one looser than the rest, will be a gushin. Tight bearing will just see a light flow. Warning. This can be messy. Prepare accordingly. And it does work. And then there is PlastiGage, and or mikes.Jim