Rebuilt 964 engine not making oil pressure
 

Hello, I was hoping to start my engine rebuild for the first time today, but it looks like it isn’t getting oil from the main oil line. Per Wayne’s rebuild book, I pulled the DME relay and cranked the starter in 30 second intervals in order to pre-oil the engine, but my instrument panel never indicated any pressure and the oil warning light never went out. I probably did six or seven 30 second intervals, never more than 3 at a time and resting the starter between each interval.

I then checked the main oil line to the engine and found it to be completely dry. I then checked the crankcase drain plug and the oil pressure relief pistons, and all indications are that no oil has been pulled into the engine. I’ve been using the Rothsport check valve in that main oil line for several years now, and I confirmed there was oil on the other side of the valve and that the valve was functioning and installed correctly. The oil relief pistons are both new and appear to work normally as well.

Any thoughts as to what could be causing this?

Am I just not cranking the starter long enough or in close enough intervals to get oil pressure?

Could I have mistakenly left out one of the oil pump to crankcase seals during assembly?

Thanks

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Main oil line in question is behind heater pipe, note Rothsport check valve

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993 oil system (similar to my set up with the additional 993 console)

Try tracing the oil flow starting at the tank to see how far it's getting (or not). For example -
1. oil in tank? Check.
2. oil at line where it connects to engine
Etc.

Sounds like you may have failed at #2. Blockage in oil line? Did you put a plug or stuff a rag in there while the engine was out?

On earlier engines, one good way to check oiling before starting a rebuild is to loosen a cam oil line or pressure fed tensioner line, and watch for some oil to come out. If I have it right, you don't have external cam oiling lines. But you should be able to loosen up quite a bit the oil pressure sensor and watch that while cranking.

I'd expect you'd get oil to the bearings quite a while before oil would get into the sump in any quantity.

Do I understand that you pulled both of the pressure sensor plugs and springs and pistons, and all that was dry? That would indicate oil is not getting out of the pressure side of the pump for sure. Did you crank with these - especially the horizontal one, which is the lowest, out?

Ordinarily, if you just filled the oil tank and let the car sit for a day or so, you should get oil - quite a bit of it - out of the sump. But you have the Rothsport which prevents that. I'd consider temporarily replacing it to see, because the option of pulling the engine apart again is not appealing.

Also, without the Rothsport I would expect that you'd get oil in the sump even if you left off the pressure inlet seal - that would let gravity push oil in faster than usual. And I'd think the pump would be able at least to push oil into the case up to the lowest of the places it could get back to the sump from.

If the inlet seal was absent, I could see that not enough vacuum would get to the Rothsport to open it?

I've always put some assembly lube into my pumps and spun them before installing. While I would suppose that even dry they would pull the needed vacuum to open the Rothsport, maybe not? Another reason to remove the Rothsport while checking this out?

Short of an engine disaster, the shafts which drive the oil pump ought not to break (I had one break, but that was due to a rod bash a hole in the oil pump). Hard to imagine overlooking forgetting to install the splined tube. But you can see if turning the engine turns the pump. You can remove the scavenge output tube and look in and see those gears and if they move. A borescope would help here (you can buy one you can attach to a laptop for less than $10). For that matter, if you pull the inlet hose, you can get a borescope right in to watch the pressure side gears turn in the pump. You might even be able, if you bought a slightly fancier scope with a 90 degree mirror you can attach, to inspect the joint where the seal goes. You might be able to see the color of your seals at the joint, or their absence. This would be another way to be able, by jacking up the right side of the car, to pour some oil directly into the pump.

This would scare the willies out of me, too.

One of the pump seals fell off location when you mated caves halves....
Bruce

Sometimes those seals are too short and will cause the same problem.

Mechanical pressure gauge.....
 

Install a 5-bar mechanical pressure gauge at the pressure sender location and crank the motor. You should see the gauge move and register some pressure reading. If the gauge does not move at all, you have no oil pressure during cranking.

Tony

I'm sure you have seen this before and am not going to dispute your diagnosis. However, wouldn't the seal under the pump, as shown in my motor, be the one that was left out? Even so, oil would flow into the crank case, correct?

I would use a bore scope to confirm the placement of the seal.
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try and remove the rothsport valve. The dry oil pump cant pull any vacuum to suck the oil past the valve. this is based on your comment " I then checked the main oil line to the engine and found it to be completely dry" . The oil pump needs oil to help it seal. At cranking speeds with no oil air will just leak around pump gears.

john

Those green oil pumps seals have been problematic. We use the brown Viton ones.

I vote for this test too. Then crank and look for oil pressure. Much easier than disassembling the engine. I saw the suggestion to check for the seals with a bore scope. Won't the seals be hidden from view in the recesses in the pump and crankcase?

They are visible if you go in through the oil passages. On one of my assemblies, I was worried I had one come loose. A bore scope showed them in place. Since there is no oil in the motor this could work.

But I agree, in this case there doesn't appear that oil is getting to the pump.....

Thanks all for the advice. Today I hooked up a pre-luber to the oil temp sensor bung on top of the engine to get some oil in there before attempting to crank the engine again. This caused oil to spill out the main oil line fitting on the bottom of the engine. Would this indicate either:
- oil finding it’s way back out through the pressure side of the pump
Or
- that I forgot the seal between the pressure side of the oil pump and the crankcase?
Of all the oil pumps seals to have forgotten, that’s actually the one I’m most confident I installed.
Regardless, now that I’ve removed the Rothsport check valve, do you think I have anything to lose by cranking the engine again to see if I can get some oil pressure with these changes?
Thankshttp://forums.pelicanparts.com/uploa...1549162468.jpg
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Interesting muffler arrangement.. what is it?

I'd argue no harm in attempting cranking to see if you get oil pressure. Plugs out for better cranking speed and to make sure it won't start in case no oil pressure still [edit - saw you pulled the DME relay to cover the second part]

Almost have the engine all reinstalled again, will crank for oil pressure by the end of the week and then attempt to fire the engine if all goes well.

Muffler is a B&B system with a ceramic coating. The headers seem fine, but the muffler drones and I don’t recommend it.

Those green oil pumps seals have been problematic. We use the brown Viton ones.
__________________
Steve Weiner

My ol' pal Steve misspoke; as the Green oil pump o rings are Viton, the Brown more common ones are silicone . We have never had a problem with either, though about 20 year s ago one supplier had some got out that were off dimensionaly and created problems for others.

Walt had good advice; look into the oil inlet to the pump and verify it is turning as you can see the gears on that side of the pump w the inlet line removed(unless you have put a manual gauge and it and found you had pressure already at say the oil Press warning light port or somewhere on top of the case).

If you have oil pressure up top you should be fine to start it . Backtracking-You mentioned the valves on the bottom and side of the case and you might verify using the manual that you have them correctly installed while you have the oil out if this is still the case.

Kevin
GAS Motorsport

I think brown can be Viton too? Dark red/orange is silicone (like the originals?) and those suckers are rock hard many many years later when the engine comes apart.

Below is a better diagram of the oil system so we can see the paths the oil is taking when you pressurize it from the top of the engine at your oil temp sensor location. This location where you're connecting your pressurizing tank is the same location as the thermostat housing shown in the older engine. The main oil line fitting on this older engine is at the bottom of the oil cooler

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I think the oil is coming out of the main oil line fitting because it's the path of least resistance. It's fairly easy for the oil to puke out of that opening since it is a very direct path from the top of the engine through what I refer to as a "J" pipe cast into the engine case. That J-pipe leads directly to the outgoing side of the pump's pressure section. With your pre-lube setup, you're effectively pushing oil backwards through the pump.

I believe that if you were to temporarily cap the main oil line fitting, you should get the pre-oiling results you're looking for. The pressurized oil at the top of the engine should flow through the next path of least resistance which is the engine case gallery onward to the crankshaft passages. Actually I think you should have already been seeing a little bit of oil flow through the engine case gallery.

With all that cranking you did, I would expect the oil warning light to go out. The warning light switch has a VERY low pressure threshold and is a normally closed (NC) type switch. So any little bit of pressure will open the switch and turn out the light.

That was a good point to verify the pump is actually turning.

It seems hard to believe oil can’t make it from the tank, to the pump, and not flow into the engine.

This is a very basic system. So something basic is wrong. Unfortunately.

Quick update: this week I was able to get normal oil pressure to register after removing the Rothsport check valve, so it certainly seems like that was the root problem. My buddy and I actually got the engine started yesterday, but quickly noticed that the fuel return line was leaking...which means I get to drop the engine again today. Engine sounded good though for the brief time it was running. Thanks again to all for your help..

Good to hear it is making oil pressure.

Odd that the check valve didn’t work properly.

I wonder if the “dry” pump wasn’t able to pull enough suction to prime itself. It may have been pushing air and couldn’t create suction at the inlet.

I assume you have no desire to put it back in.