Prime oil on rebuilt engine

[buster1015]

I finished a top end rebuild on a 1987 911 turbo and following Wayne's engine rebuild book it suggested I disconnect the DME relay and crank the engine over to circulate the oil before starting. I tried that in 30 second intervals but I couldn't build any oil pressure and the oil light never went off. I took out 1 spark plug from each cylinder to make the starter's job easier but still no luck.

So far, about 11 quarts of oil have been added and the oil tank level is between the target marks so it seems to have move partially through the system. I do have a large front mount cooler and large oil lines so I estimate total capacity is over 14 quarts. I unhooked one of the cam oil lines and placed it in a zip lock bag while I turned over the engine and I did get a bit of fresh oil. Not as much as I expected so probably a mix of oil and air.

Battery is on the charger overnight. Should I crank it again tomorrow or is there something else I should check first?

[bigel]

I'm also interested as I will be doing the same (though not turbo) this winter...

[E Sully]

If the gage is not moving I would try cranking it a few more times. On my '86 rebuild it showed pressure on the gage fairly quickly, but I only had the standard cooler.

[ajwans]

You front mount cooler will make no difference while the oil is cold.

andy

[Flat6pac]

But if you knocked off one of the gaskets on the oil pump when you were putting the case halves together.....
Been there, done that
Bruce

[Ronnie's.930]

911 Turbos/930s don't have DME relays (K Jetronic/CIS system) . . .

[buster1015]

With the battery fully charged I cranked it a few more times but the oil pressure needle won't move nor will the oil light go out. Both sensors are plugged in and when I turn the key the needle moves from rest up to zero.

I didn't split the case halves for the rebuild so I don't think I could have done anything to affect the oil pump. Had no oil pressure issues prior.

My car is a 911 Carrera but the engine is a 930 twin turbo so it does use the DME and Carrera intake.

I'm not sure what else to do at this point.

[Flat6pac]

Well, If you didnt split the case there shouldnt be any oil pump seal problem. I would go ahead and fire it because the problem has to be in the info circuits.
In the car, the most pressure will be the feed to the turbo. Crack the feed line and see that you have good oil flow.
Bruce

[JFairman]

Being on the bottom it may be easier to remove the turbo sump tank oil line(s) and put a cup under it to collect the oil. You'll be priming them and you'll see they're getting oil pressure.

[porterdog]

FWIW I've had to crank for 30s or so before seeing pressure after an oil change on my 964 (note that usually the engine sits for a week or so before I refill it, so it really is empty.) The one time I fired it instead of just cranking it clanked like crazy; *not* happy.

[buster1015]

I decided to first confirm that my oil pressure sending unit and gauge are working. I pulled the sending unit off the engine and with an air compressor line and random rubber boot I pressurized it and the gauge on the dash reacted accordingly. So, sensor working but no measurable oil pressure at the oil sensor.

I found these two oil circulation diagrams on other posts. I have confirmed (accidentally) that the scavenge pump is working because when I cranked the engine I forgot to re-install the oil filter and there was plenty of oil in the engine compartment where the filter goes.

So, to check pressure pump I removed the oil relief valve plunger (#4) and cranked the engine. There was definitely flow and a descent amount of oil in the catch can but I'm not sure if that confirms the pump is functioning properly but it is moving oil.

I pulled one of the turbo oil return lines (goes back to the sump) and I'm getting no flow. I'm wondering if the pressure pump could move oil but not generate sufficient pressure? I don't really see how this could happen since everything functioned fine before the rebuild nor how to test. If I install an external oil pressure tester in place of the relief value (#4) the oil would take the path of least resistance back to the sump (#2) so very low pressure on the gauge.

[rsscotty]

Just asking...when engines are removed usually there are rubber or plastic plugs put in the oil cooler or the "S" hose. Any chance there is one left in the oil supply circuit?

[buster1015]

Well, that is a good thought. Some sort of obstruction is a very plausible cause. In this case I didn't use any plugs or caps during the work so that isn't it. I think I'll get a scope to look through the oil passages and just work through them one at a time.

[rsscotty]

If the s hose is taken off the large tube on the bottom of the oil cooler you should be able to look into that tube with a flashlight and actually see the gear on the oil pump. That would be a start, and then see if the s hose has clear flow.

[buster1015]

Looks like rsscotty's suggestion solved the issue. I pulled off the s hose and it was clear but the feed pipe to the pump was not. There was a paper towel deep inside which I just finished removing. I must have used it to stop the oil cooler from dripping oil and some how didn't see it during assembly.

[KTL]

Wow............ Great failure avoidance and great suggestion by rsscotty.

[MBruns]

I had a tech working for me that did a simple clutch job on a 3.3 turbo, he finished the job in normal time, but spent 2 days trying to diagnose the no start, turned out he used a red cap on the fuel filter feed hose and failed to notice when installing. I always put caps OVER the hose etc.. He never had that problem again ! You were very lucky that you found that paper towel

Mike Bruns

[E Sully]

Now do we get to see the first start on video? Pressurize the fuel system and check for leaks first, and don't forget the fire extinguisher. I also needed a fan to clear the smoke for the first 15 minutes on initial start up after my rebuild.

[buster1015]

I did the first startup but found a minor oil leak at the oil pressure sending unit because I reused the aluminum washers so had to shut it down rather soon. Sounded mean and the smoke wasn't too bad. I'm picking up new washers from PP today and will start it back up tonight. If I remember, I'll setup up a camera to record it.

I'm very thankful I didn't rush and start the car with the blockage since the damage would have been catastrophic.

[buster1015]

And the first successful startup. Now it's time to start breaking it in and setting the piston rings with some boost.

Porsche 911 twin turbo startup - YouTube