The Mitsubishi Pajero Owners Club®

azmonty · Posted: Thu Mar 26, 2015 4:46 Post subject: 6G72 Oil pump question

I own a 1994 Montero LS, SOHC, 3.0.

I have zero oil pressure. I replaced the pressure transducer, checked the wiring and ohm reading at the gauge. All is as it should be. I decided to replace the oil pump, no easy task. However, something that has bothered me is this. The oil pump drives off the crankshaft, yes. But how? I ask this because when I went to remove the crank bolt, it was loose. Apparently the dolts why did prior engine work before my purchase forgot to torque it. This got me to wondering. If there is no key way or anything connecting the pump directly to the crank, is it done by compression through the crank bolt? If so, then the crank bolt may be the problem and not the pump itself. I am trying to avoid removing the pump if I don't have to. I have everything torn down to the point of doing the front axle to remove the oil pan.

Any ideas?

Cheers, John

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magn1t · *** Joined: 07 May 2006 Posts: 153 Location: NZ

It won't be the pump.
The pickup might be blocked or loose.
The bypass valve might be jammed open.
The bearings might be toast.

But whatever......have you read the manual?

azmonty · Posted: Thu Mar 26, 2015 17:11 Post subject:

Thank you for not answering my question. Which was quite specific.

Of course I have considered the pick up, however, I will still have to remove the oil pan to access it, which I was trying to avoid if there was another option. I also considered the relief valve, which is possible. I also considered the bearings, which has just been replaced.

I have been working on cars since I was 16, I am 62 now. I built aircraft for 25 years. So I can read.

I have the factory manual and yes I read it, however it's not as complete as expected. Since I have to access the pick up, which could be the issue, I might as well replace the pump and timing belt at the same time. The belt was replaced 15,000 miles ago. I figure if I have everything removed for access, I might as all replace everything I can see.

My question had to do with the drive mechanism. This pump setup is similar to my old SAAB 900, driven off the crank. Of course SAAB's are back asswards, which made access to the crank bolt problematic.

Regards,

John

peteinchad · Posted: Thu Mar 26, 2015 18:25 Post subject:

Azmonty - I've sent you a pm - please check your messages.

trekker · Posted: Thu Mar 26, 2015 18:34 Post subject:

There doesn't seem to be a key, but a detailed look at the Mitsu drawings seems to show a flat on the crank where the inner rotor sits.

I don't believe the rotor drive will be just friction.

But I don't run this engine, so I can't help further. Pity you can't view an inner rotor at a breaker or Mitsu dealer.

azmonty · Posted: Thu Mar 26, 2015 18:50 Post subject:

Thx, after searching through multiple sources I did find that flat spot on the rotor. The Mitsu dwg does not show it, hence the question. It did not make sense that it might be compression, but I've seen stranger engineering before.

I was trying to avoid having to drop the axle, then the oil pan to remove the pump if I did not have to.

I would not be surprised to find a rag in the oil pan blocking the pick up given the kind of workmanship which was done prior to me buying it.

When I find the crankshaft bolt, finger tight, red flags start flying all over.

trekker · Posted: Thu Mar 26, 2015 19:25 Post subject:

Yes, or the pick up pipe is loose, cracked, or no gasket where it attaches to the the pump.

Having no pressure to me rules out wear, perhaps something missing like piston cooling oil sprays.

Does the engine look as though it's been stripped ?

Let's know what you finally find.

dave

azmonty · Posted: Fri Apr 17, 2015 0:11 Post subject:

Okay, finally got the oil pump off, still working on getting the oil pan of. Am close. The oil pump appears to be original. I removed the relief valve nut and spring. The plunger is stuck inside all the way to the top.

Will replace the entire pump assembly as it is. Once the pan is off, will retorque the mains. I have no faith in the work previously done since the crankshaft bolt was finger tight!!!!!

trekker · Posted: Fri Apr 17, 2015 10:28 Post subject:

Looks as though you have found the culprit, is it jammed with sludge ?

Yes, a good opportunity to torque whatever bolt and nut you can find with the sump dropped.

Let us know what you find and how your oil pressure is once you've fitted the new pump and relief valve.