Sheared oil pump shaft with 993 pump

[neilca]

I have been struggling for a year now with this new 2.4 liter race engine. My biggest problem has been the crankshaft sensor for the engine management system. Well today I solved the problem with a Hall effect sensor and a really nice trigger wheel from a Ford. I was warming the car and it was running great. reved it and noticed afterward that my oil pressure was stuck on 10 psi. Shut it down, changed the oil filter, no change, checked both oil relief valves and they were OK.

Is it possible that I sheared the oil pump shaft when I reved it at 140 degrees F oil temp? Is there any way I can check it?

This engine has not had oiling problems and has been on the dyno a couple of times.

[E Sully]

Have you verified the gage or sender is not the problem? By itself, I can't see how revving the engine with 140' oil would cause a problem. Did you check the level of the oil in the tank to see if the scavenge side of the pump is returning the oil?

[stownsen914]

Strange problem. Certainly a big one if the pressure is actually that low. I'd suspect the gauge or sender first. Maybe check connections for all of the above (especially grounds on gauge and engine), since that's easy to do. A sheared pump shaft would give zero pressure I'd think?

Could a stuck or damaged oil bypass spring or piston cause low pressure?

[neilca]

I do not suspect the gauge since it was working when I fired the engine.

I did check the pressure relief valves

Can the engine internal thermostat cause something like this?

[KTL]

Sorry to hear this Neil. T-stat should not cause the pressure drop. Open, closed or in between the oil has a path to go.

If the pump shaft sheared on the splines, I think you'd get some abnormal noise from that?

Any signs of distress inside the filter? You can check for pressure by looking at the case fitting near the t-stat. This column in the engine is the next place the pump delivers oil to after the t-stat bore





I suspect that's where your pressure gauge gets its signal? If it's only 10 psi, you'd be able to tell pretty easily with an alternate gauge hookup.

[earossi]

+1 for Keith's reply. How did you check out the relief valves? And, how did you determine them to be OK? You could have one hanging up, and extracting it for a visual inspection may now show anything.

Second, you mentioned changing out the oil filter. You should cut open that filter to determine if there is any metallic debris that was captured.

If the motor still runs well and there are no noises, than I really do suspect the pressure measurement.

Just my feeble thoughts.

[neilca]

I pulled the new oil filter off and found it did have oil in it, so oil is circulating. I am going to check my gauge today.

I disassembled the pressure relief valves and the pistons moved freely in the bore. No debris was found. What else should I do to verify they are working?

Also with the oil I have already encounter no metal is present.

[earossi]

Verify that you have the relief springs in the correct holes, since they may not be the same lengths. Also, use a long magnet to move the pistons in their respective bores. Make certain the piston bottoms out without hanging up in the full length of the bore.

[neilca]

Well the mystery is solved. Ed Sully nailed it, the gauge. Apparently, when I installed the sender the Teflon tape was pushed into the engine. This tape worked it's way over the hole in the sender causing a blockage. Once that was cleared all the oil pressure came back. Scared the hell out of me.

Thanks guys for the support.

neilca

[stownsen914]

Ha, excellent reason for low oil pressure reading. And happier than other alternatives, too. Glad to hear it worked out nicely ...

[KTL]

Yeah that teflon tape is more trouble than its worth. Do yourself a favor and use the thread sealant paste stuff instead. Stays on the threads MUCH better and you only need to use a tiny bit of it.