Unable to prime oil pump 3.9 litre V8

[Richard Kaye]

I have rebuilt a 3.9 for my 1988 RRC and installed it. Started it up and ran it for about 20 seconds but I cannot get any oil pressure. I had packed the oil pump with Vaseline prior to startup, this method has always worked for me but not this time. I then removed the distributor and used my oil pump priming tool with the drill. Tried for about a minute and still no oil pressure.

I found another oil pump in the shed, packed it with Vaseline and put it on, still no oil pressure using the priming tool.

I filled an oil filter with oil and put that on, but it didn’t help either. I removed the sump thinking that the oil pickup may not be on properly and sucking air, but the pickup was all ok. Also tried removing the oil pressure switch and filled that cavity with oil with a syringe.

Not sure where to go from here. Does anyone have a method to get oil pressure which I have not tried? How long does it take to get the system primed using a drill and priming tool, maybe I need to wait a bit longer when priming.

[PhilipA]

Have you got the correct timing cover gasket? One has a hole for the oil pump and one doesn't.
Regards PhilipA

[Richard Kaye]

I went back through the gaskets I bought, and it looks like the timing case cover gasket is an ERR4936.

[Richard Kaye]

Did some more digging and it looks like I ordered the STC2823 bottom end gasket kit, I should have ordered the STC1639 kit. This is probably why I can't get oil pressure.

[Richard Kaye]

It is not the ERR4936 that I have, it's the later type.

[loanrangie]

It is not the ERR4936 that I have, it's the later type.

So you might have the gasket that fits the later crank driven oil pump which as Phillip said wont have the hole for the oil passage.

[Richard Kaye]

When the rain stops I am going to remove the timing case cover and see what is going on in there.

[Richard Kaye]

I removed the timing case cover this morning. The gasket doesn't have the extra hole but neither did the block???

It's a 3.9 engine code is 38D, I think that means it's the serpentine belt motor with the crank driven oil pump. When I put the motor in originally about 2 years ago, I used the 3.9 block but everything else, including timing case cover and oil pump, were taken off the 3.5 and bolted to the 3.9. The provision for the extra hole for the oil pump is in the timing case cover, but no corresponding hole in the block.

Don't understand why it got oil pressure straight away last time I put it in, now I can't get anything.

[350RRC]

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Don't understand why it got oil pressure straight away last time I put it in, now I can't get anything.

Are you going by the oil pressure gauge or a rattling motor?

DL

[Richard Kaye]

Both, the motor is rattling, and the oil pressure light won't go out.

[loanrangie]

I removed the timing case cover this morning. The gasket doesn't have the extra hole but neither did the block???

It's a 3.9 engine code is 38D, I think that means it's the serpentine belt motor with the crank driven oil pump. When I put the motor in originally about 2 years ago, I used the 3.9 block but everything else, including timing case cover and oil pump, were taken off the 3.5 and bolted to the 3.9. The provision for the extra hole for the oil pump is in the timing case cover, but no corresponding hole in the block.

Don't understand why it got oil pressure straight away last time I put it in, now I can't get anything.Hole is in the cover because the pump is on the cover, later cover doesn't have provision for the pump.

[Richard Kaye]

Should there be a passage in the block 181393corresponding to the hole in the gasket (green hole in the picture)

[Richard Kaye]

181394

[Richard Kaye]

I have had a look at the oil pump and measured the clearance between the gears and oil pump with some plastigauge. The measurement came to 2.5-3.0 thou.
Also ordered the correct timing case cover gasket. Checked the pickup to make sure it wasn't blocked, and the passage in the timing case cover from where the pickup runs into the oil pump. I will come up with a method to check the output from the oil pump to the block oil galleries to make sure there is no obstruction in there.

[Richard Kaye]

Ended up putting a new timing case cover gasket and put the sump and oil pickup back on. I filled the oil pump with Vaseline (again) and filled the oil filter with oil. Got the 240-volt drill onto the oil pump drive. Took about 5 seconds to get oil pressure, left drill going for about 2 minutes.

I don't know what changed, the timing case cover gasket I put on had the same holes as the one I took off. I think I may have had an air leak where the oil pickup bolts to the block.

Probably never know why.

[Phil 850]

Glad to see you resolved the issue.
Nothing worse than faffing about without getting a solution.

[Richard Kaye]

Got the Range Rover started this morning, instant oil pressure as it was cranking. Now to tune it, went from 8.13:1 compression to 9.8:1 compression (That was the point of the whole exercise). I have a BLOS LPG mixer and a CB Blackbox programable ignition with 411 boxes to be filled with timing figures for rpm vs intake vacuum.