ThetaTau87

I took my car to a track day about a month ago. It ran flawlessly for the first two sessions. Just before the third session someone commented that my car was burning some oil at WOT. I checked the oil and it was near the bottom line on the dip stick. I topped it off to the top line.

First lap out for the next session I noticed a huge cloud of white oil smoke coming out my exhaust as I came down the front straight after completing the lap. I let off to brake for turn 1 and then got back on the gas and more smoke and a serious loss of power. I pulled off the track and turned off the engine.

When I tried to restart it would crank but not fire and was cranking slowly. I trailered it home.

When I got home I started to diagnose. The plugs were covered in oil. I checked the compression and got results that made me suspect the gauge was bad. The first reading I got on #1 was 135 psi, but the other cylinders were all over the map and different each time I measured them. Some were around 100 psi and others were as low as 50 psi. The engine was cranking slow so I thought that could also be a cause of the erratic compression numbers aside from a bad gauge. I got out my leak down tester and got consistent 16% leak down on all cylinders with a cold engine. This made me confident that nothing was wrong with the engine internally.

I cleaned the plugs with brake clean and compressed air and reinstalled them, but the engine still wouldn't fire. The plugs came out wet with fuel after extended slow cranking. I verified spark on both banks of cylinders with a timing light. I removed the upper timing belt covers and verified that both cam marks lined up and that the crank was at TDC. The engine turned over easily by hand with all the plugs removed.

Next time I had a chance to work on it I verified that the oil was caused by the PCV port on the passenger side cam cover sucking up oil. There is a long left hand turn right before it started billowing smoke. I removed the air filter and MAF and cleaned out a lot of oil that had pooled in the bottom of the intake behind the throttle body. I removed the plugs again and cleaned them again this time by heating them with a propane torch to burn off all the oil residue. They looked great when I put them back in, but the engine still wouldn't fire and was cranking very slow despite the car having been on a battery tender for a couple weeks and showing 12.7 volts.

I tested the battery and found it had a bad cell. After putting in a new battery the engine cranked at normal speed but would still not start. The plugs were still all wet with fuel.

I replaced the fuel pump and LH #53 relays with brand new parts with no change. I installed a brand new set of plugs and swapped a pair of LH ECUs that I borrowed from another 928 owner. Still no start and wet plugs. I verified spark at all 8 cylinders with a timing light.

I rechecked the compression and got numbers ranging from a high of 70 psi to a low of 35 psi. Again the numbers were different each time I tested the same cylinder. #1 that measured 135 psi when I originally did a compression test was now only making 65 psi. The engine was cranking fast and I was using a battery charger with a 125A engine start booster mode to ensue that the battery didn't loose charge while testing the compression. This makes me think my compression tester is junk or that the cylinders are getting washed down with fuel and lowering the compression.

Not sure what to try next. I've never experienced an engine that has spark and fuel, but won't start. It won't even cough or pop.

Is it possible that the PCV sucked up enough fuel to hydrolock the motor and bend rods? It didn't make any nasty noises when it was blowing the smoke. It was just down on power and a little sluggish. When I pulled off the track it was idling good until I turned off the key. Bent rods seems like a long shot, but I don't understand why it won't fire at all and why the compression numbers were so inconsistent the first time and extremely low when I tested them again today a few weeks after the first time.

Mrmerlin

based on the compression numbers you have a jumped timing belt ,
I would be looking at the driverside cam snout to see if it has snapped, and is being held with the bolt.
NOTE all of the valves are bent.

You could also pull plug one and verify TDC and where the cam lines up.

do the same for plug 5,
NOTE the rotor will be pointing at plug 5 in the cap when the piston is at TDC for plug 5

y33trekker

Disclaimer - Pretty close to a total novice in the 928 world at this point here.

That said, the white smoke indicates burning coolant, so I'd suspect a coolant leak (possible cracked passage) somewhere in the area of the intake manifold that is watering down your fuel and preventing it from igniting.

Ever noticed since the first time you had to top it off any coolant getting mixed in with your oil? Possible blown head gasket? (That would account for your erratic compression checks).

I'm not all that familiar with the intake/coolant system layouts on the 928's just yet or maybe I'd be able to be more specific, so right now I'm just spitballing based on Engine Stuff 101.

Hope it's nothing really serious.

ThetaTau87

The smoke was definitely oil. The color was white because there was so much oil that got into the intake. It looked like a smoke screen it was so thick. It smelled like burning oil and I found lots of oil in the bottom of the intake. I didn't loose any coolant and there is no pressure escaping the cylinders into the coolant system when I did the leak down test.

SeanR

I'd yank the engine, get it on a stand and go through the entire thing. I know it's not what you want to hear but I'd be willing to bet you have a huge paper weight right there.

ThetaTau87

I verified that the timing belt is good and the marks on the cam pulleys line up with the marks on the valve cover when the crank is at TDC. If the belt had jumped the marks would be off.

If one or both of the cam snouts had snapped wouldn't there be at least one cylinder on each bank that had zero compression due to the valves being open? I got the same leak down and at least some compression on every cylinder.

Rob Edwards

Pull the oil filter, cut it open, look for metal flakes. If you don't see visible flakes in the oil, send off a sample to Blackstone for analysis.

I guess the second thing I'd do is get a $15 Ebay borescope, rotate each cylinder to BDC and look at the bores to make sure all is in order, no gouges, broken lands, etc.

Stock bottom end? No pan spacer? Best case scenario you just overfilled it (oil at the top line on the dipstick is fine for the street but guaranteed to generate a lot of windage at sustained high rpm) and fogged the track with oil smoke as oil backed up in the heads and up into the intake. The problem with that is you're inducing a lot of detonation at the same time your rod bearings aren't getting a lot of oil.

Any recollection of what the oil pressure was like on track?

Pull the plugs again, put the car in neutral, and put a clicker torque wrench on the crank and figure out how many ft-lbs it takes to turn it over.

BC

How about a better compression tester.

I feel concerned over your being sure about spark.

White smoke that is billowy like clouds is coolant.

White smoke that is thinner and blue or grey is oil or hydrocarbons.

Rob has some good ideas on visually determining where you are.

GregBBRD

^^^^^^^^^^^

This is your next step. Oil filter inspection is what you need to do next.

Stock 928s will not survive on the track.

They should have put that information, in the owner's manual.

GT cars. Not for use at WOT on long stretches of highway, not for any track use.

I've got dozens of special pieces to allow these cars to be used on the track. There's an entire combination of different things required....not one magic solution.

ThetaTau87

Stock bottom end and no pan spacer. The oil pressure was good every time I looked at it, but I wasn't watching it all the time and I didn't check it after the smoke started before I turned it off.

I'll check the torque to turn it over tomorrow when I'm back at the shop.

BC

Even with street tires, sliding around with only momentary g-forces?

docmirror

You have spark but you don't know if it's at the right time. Put a timing light on it, and check the ignition timing by the pointer on the balancer. Do the same for cyl 5 and check it's timed right. If that's ok, then it has to be injection. Are the plugs wet with fuel or with oil? Hard to believe it's fuel. Try cranking while spritzing some carb cleaner into the MAF and see if it comes to life. Report back on those findings.

I'm guessing with your bad comp results , you either have a goofy gauge, or you have valve train issues.

ThetaTau87

The plugs are wet with fuel.

MFranke

Did you look at the cam chains?

ThetaTau87

I have not looked at the cam chains yet.