Can't build any oil pressure after replacing all oil lines-90 964

[tailwind22]

I've tapped the braintrust over on Rennlist 964 forum as it is a bit more active than the Pelican 964 forum. Thought I would try here. My car is a 90 964. PO had the motor rebuilt 3000 miles ago and I strong oil pressure and performance. I started a header and exhaust install and discover several of the oil circulating lines were weeping. So I drained the oil and replaced all lines that circulate oil including the oil cooler lines. Not a fun process but got it done. Put about 10 quarts in the system since everything was dry. Pulled the lower spark plugs and fuses for the DME and fuel pump and started repeated cranking runs. increasing up to 30 seconds continuous and resting starter. No pressure was indicated at the oil pressure gauge (which had been behaving well). Here are the following steps after that:
-pulled oil filter to verify oil had moved from the oil tank to the motor and back up
to the filter ( was about half full of oil)
-removed the base holding the oil pressure sender and verified an oil level at the
opening about 3/4" below
-hooked up mechanical gauge and went through the cranking process again. No
pressure just some very slight movement of the gauge needle.
-installed a fresh sending unit (Porsche Genuine) so I wouldn't have to go back
there again. More cranking, same result.
I have not checked the oil pressure relief or safety valves but all was working fine previously.

I'm out of plays and am asking the braintrust for ideas on next steps.

[mikedsilva]

does the oil pressure 'idiot' light go out when cranking?

[r lane]

Dont know if this applies to the 964 as its plumbing differs from its predecessor, but the oil flow valves that some put in the pressure line to the case will not flow if there is no oil at the pump. In case you are using one. Bob

[tailwind22]

Originally Posted by mikedsilva

does the oil pressure 'idiot' light go out when cranking?

Light stays on

[tailwind22]

Originally Posted by r lane

Dont know if this applies to the 964 as its plumbing differs from its predecessor, but the oil flow valves that some put in the pressure line to the case will not flow if there is no oil at the pump. In case you are using one. Bob

No check valve in place. I know those have caused some problems when the system is dry.

[stownsen914]

With this comment, I assume that the filter on a 964 is in the scavenge circuit (I'm more familiar with earlier models) ... seeing oil at the filter wouldn't be relevant to oil pressure on your gauge (which measures the pressure circuit), so don't base anything on that.

A couple thoughts:
So you've only cranked and not tried to start? You mention seeing a tick on the mechanical pressure gauge. Did you get that on the cockpit gauge too? Ideally I'd like to see 10 psi or something, but you may not see that just cranking on the starter, even with the plugs out.
If you've got oil at the sender (or just below), then clearly oil has gotten where it needs to be. If you want to be more sure, crack the sender or another fitting loose and see if oil comes out when cranking. If it does, I'd tighten it back up and give a try starting. Obviously make sure you get oil pressure immediately upon startup, or shut it down.

[Flat6pac]

The concern being that you’re not showing pressure on the sender which is located right above the oil pump at the thermostat.
Did you plug the inlet when changing lines?
Do you have flow? You need flow before pressure builds up.
Just thoughts,
Bruce

[tailwind22]

Originally Posted by stownsen914

With this comment, I assume that the filter on a 964 is in the scavenge circuit (I'm more familiar with earlier models) ... seeing oil at the filter wouldn't be relevant to oil pressure on your gauge (which measures the pressure circuit), so don't base anything on that.

A couple thoughts:
So you've only cranked and not tried to start? You mention seeing a tick on the mechanical pressure gauge. Did you get that on the cockpit gauge too? Ideally I'd like to see 10 psi or something, but you may not see that just cranking on the starter, even with the plugs out.
If you've got oil at the sender (or just below), then clearly oil has gotten where it needs to be. If you want to be more sure, crack the sender or another fitting loose and see if oil comes out when cranking. If it does, I'd tighten it back up and give a try starting. Obviously make sure you get oil pressure immediately upon startup, or shut it down.

I should have mentioned that during this process I have bumped the engine on and shut down immediately when no pressure was shown. Didn't know if the oil level at the sender flange port should have been all the way up level or if 1" below was to be expected.

[tailwind22]

Originally Posted by Flat6pac

The concern being that you’re not showing pressure on the sender which is located right above the oil pump at the thermostat.
Did you plug the inlet when changing lines?
Do you have flow? You need flow before pressure builds up.
Just thoughts,
Bruce

So I did use some plugs when changing the lines. Most were plastic over the inlet covers that I had. I couple were rags. With the rags I left excess hanging out so not to forget they were there. So 99.5% sure there were no blockages (it's that .5% that always worries us, right?).

Let's say something got left in the engine inlet line. Best shot to see that would be to drain the crankcase and look for something to come out or maybe irregular flow out of the engine? I almost feel that is now my next step.

[stownsen914]

Agree that looking for blockages is a good next step, I should have mentioned that. Luckily the oil feed path to the engine is short. You can disconnect each hose to double check them. And then at the engine, a visual inspection as you suggest and use a light and/or compressed air to check for restrictions like a piece of a rag, etc. that could get sucked into a blind passage. Basically just follow the path from the tank to the oil pressure sender.

[MoreGAS]

On a 964 engine you can remove the inlet line from the tank to the case(pass side low w RR wheel off) at oil entry in to the oil pump and look straight in to it with a flashlight and see the gears of the pressure side of the pump...I am 95 % certain of this and this is the case on an aluminum case sandcast we built a 2.9 in to....the oil light came on while I was driving(luckily not the client who may not have been as mechanically sympathetic) it on the racetrack and I shut it off within seconds when I saw the gauge at zero psi.. Long story short , in the paddock I could have someone turn the crank and I watched the oil pump gears not turning ...the drive or coupling shaft for the pump had broken(poor machining by a reputable shop to add bearings to the case for Int shaft-never used them again) . You could have something blocking your pathway or stuck in the gears of the pump, which could damage splines on the shaft. A rag would pass through them somewhat and really do damage to the pump as a buddy did that years ago and spun bearings letting it run a bit (no light as it generated some oil pressure for a little while) . Your manual guage is the answer screwed in there- no oil pressure and is always the best back up test.

Also realize that stock OP warning light comes on at 2-3 PSI which is no real help most of the time to save parts, so if you are not getting that light to shut off w your extensive cranking, you have essentially no oil pressure. We use a 15-20 psi light here for adequate warning. Your 964 filter is on the return side on a console pre oil thermostat , a little different than all other 911s where it(the filter) is on the oil tank as oil returns post oil cooler when hot. A 964 filters the oil pre cooler(s) which is nice and may get the oil more in to a solution rather than 2/3 air.

Good luck
Kevin
GAS Motorsport

Also if you remove your oil pressure sender mount plate that chamber should be full as that hole about 2/3" down from the top is the pathway for the main oil galley to mains and rods.

[tailwind22]

Super appreciate the input. I'm going to post as I work through steps in the process today. Just dumped the crankcase and nothing unexpected came out. Got a total volume of just over 1.5 qts. (see pic and I was expecting closer to 2 qts). Pulled both the pressure and safety valves, nothing unusual there. I'll try to inspect the three open inlets once all dripping stops with a borescope device. Will move on to the oil tank next and inspect the engine oil inlet as Kevin suggests.

[tailwind22]

Mystery solved. I said I was 99.5% sure the were no paper towel plugs left in. Well there was. Found this at the end of the oil inlet pipe to the engine. Looks like a big goose turd soaked in the green Brad Penn. thanks everyone. I,m predicting smooth sailing going forward.

[MoreGAS]

Glad you found it and that it stayed in one large piece. Had that broken into bits and gone through the pump you'd be in a much bigger pickle. This also explains why there was so little oil in the crankcase sump as often when it sits there are 3-4 quarts in there. You may want to look really well down through the top sender plate and use an angled pick and check that there are no paper towel bits that got through the pump and into the main oil galley. As you may know the piston squirter jetts and passageways in the crank for oil to feed bearings, and the main bearing oil supply holes, are all fairly small and a piece of paper towel could easily plug them.

l'll caution you don't try and crank it with that passage open(to see if paper towel bits come out) as one time our quick disconnect 1/4 NPT for our manual gauge we often use to chk pressure on new motors, well that disconnected on that plate and it literally shot hard to the 16' ceiling of our shop! Maybe use a hose sealed tightly and in to a bucket?

Good Luck again, almost there.

Kevin
GAS Motorsport

[stownsen914]

Well done

[Cairo94507]

Thanks for circling back and letting us know the outcome. Many happy miles.