Can't get oil pressure on 3B, even pulling with vacuum tank. (1 Viewer)

[DieselDork]

1984 BJ42. I rebuilt this 3B probably 10 years ago and finally got around to starting it about a year ago but only ran it for about 20 min. At that time I struggled to get the oil pump to prime, what finally did it was cranking (GPs removed) while a tank of vacuum sucked on one of the oil pressure sending unit ports on the right side of the engine.

Its been a year since it ran AND ITS FINALLY READY TO MOVE UNDER ITS OWN POWER AFTER 13 YEARS! and I'm in the same boat, can't get the pump to prime. Last time I imagine the assembly lube may have helped but this time around I'm sure its washed off.

So here's where I'm at: glow plugs out, fuel off, its cranking very fast on 24V with the new batteries, crankcase is 2 or 3 quarts overfull with rotella T 15w-40. the hose from the vac tank is pulling on one of the pressure sending unit holes and there is a known good mechanical pressure gauge on the other sending unit port. (also tried swapping the two)

I start cranking then throw the valve for the vacuume, the clear vac hose starts sucking oil then I close the valve while still cranking. Not so much as a twitch on the pressure gauge.

Any ideas? This method was something I came up with that worked a year ago but maybe its a bad idea that maybe ruined something?

thanks in advance!!!

-Rob

 

[duncanrm]

A few things..

• Can you get the back jacked up nice and high - I know 3Bs and 2Hs tend to take longer to build oil pressure when facing up hill..
• I've seen other people have success with some light air pressure in the crankcase via the dipstick tube, I'm not entirely convinced it works but something to add into the mix.
• The port you're using to introduce a vacuum, you should first pump oil down that port as much as you can (using whatever items you have available) - maybe one of those pump attachments for a drill if you have access to one, or can pick one up easily

I'd try all, or some of the above with your vacuum setup removed and the system return to normal .. also you wont get much oil pressure just on cranking - the factory spec for the 2H is just "> 3.4psi" at idle not sure how your gauge would show something maybe even lower than that. The 2Hs in both my vehicles do take some time to build pressure after the engine starts if they've been sitting for ages - even 6-7 seconds of idle sometimes. You may need to let this engine actually idle for a little while.

Technically, there's not much difference between the 2Hs and 3Bs..

 

[DieselDork]

Ah, good call on facing the nose down, I'll give that a shot this evening.

I thought about plugging the lifter vent tube and pressurizing the crank case but then realized that would put pressure on both suction and pressure sides of the pump for zero net force (I think).

I did squeeze some oil from a quart bottle through a tube back into the port, tried a drill pump but the oil was too thick to pump. I could make a pressure vessel from pvc, fill with oil, and use air pressure to push it back into the engine.

thanks you Duncan.

 

[Whiskerz]

For fun pull the oil filter and pre fill it.

 

[DieselDork]

Already had the filter full.

Well I raised the back way up and it did seem to be pumping a stream of oil out of the hose I had plumbed in. Based on reading some other threads here it seems normal to have pretty low idle oil pressure so I went for it. started it up and I get 5 psi at idle and up to 30 if I rev it pretty fast. Does this seem reasonable?

I have added a turbo so its oil supply may be lowering the oil pressure a bit?

Thanks again for the help!

-Rob

 

[duncanrm]

I get 5 psi at idle and up to 30 if I rev it pretty fast. Does this seem reasonable?

3B Specification for oil pressure is:

• 4.3psi or more at idle
• 36-85psi at 3000rpm
  

If you're confident with your oil pressure gauge calibration.. what is it reading at 3000rpm?

If you're at 30psi at 3000rpm I'd be slightly concerned.. perhaps the oil pressure relief valve spring could be replaced or shimmed out somehow - if its not actually pressure-relieving though you dont really have much else to play with. You could temporarily block off your turbo feed and re-assess pressure, that could give some insight.

 

[DieselDork]

Ok, cool. I have a little digital tachometer I picked up that uses a magnet and a pickup sensor. I'll cobble that on there in the morning and see what pressure I get at those engine speeds.

I swapped out the gauge I had been using (went to 75psi) for a brand new Ashcroft 0-30 psi so I'm assuming it correct. Both gauges seem to agree.

-Rob

 

[DieselDork]

Ok, cool. I have a little digital tachometer I picked up that uses a magnet and a pickup sensor. I'll cobble that on there in the morning and see what pressure I get at those engine speeds.

I swapped out the gauge I had been using (went to 75psi) for a brand new Ashcroft 0-30 psi so I'm assuming it correct. Both gauges seem to agree.

-Rob

 

[gerg]

I've had the same trouble priming the oil pump on 3Bs that sat and I got it to work by overfilling the oil pan by about 2 gallons extra, pulled the glow plugs and rotated the engine by hand to fill the pick up tube and wet the pump gears. Only takes a few revolutions.....BY HAND. Obviously don't do it with the starter. Once the gears are wet they create an air tight seal and can easily create enough Vacume to pull oil up the pick up. When the engine sits the pick up empties and the oil on the gears drains away and it can't create proper suction until wet again.
Another way is to disassemble the oil pump relief valve and pour some oil directly onto the pump gears but I feel that's more complicated.

 

[DieselDork]

Rigged up the tach today and here's what I get

Cold idle is 10 psi
Warm idle drops to 5 psi
2300 RPM is 30 psi which is as high as this gauge goes so 3000 should be well above the 36 psi per the spec.

So I'm assuming its good to go...

Thank you guys for the help, the cruiser moved out into the yard under its own power for the first time in over 15 years!

-Rob

 

[gerg]

Nice, can help your warm idle pressure by increasing the rpm. It doesn't fix worn out bearings but will help it from shutting off in the summer after a hard run.