Need CIS help... of course

[Schulisco]

The security fuel cut off switch plug is here named as the air flow switch.

[boyt911sc]

Originally Posted by PeteKz

I'm reconsidering this. I don't think the CIS is your biggest problem, maybe not even a problem.

Instead, the oil burning would get my attention now. Those plugs you pulled out have a lot of oil on them, and the "white smoke" indicates oil burning. It's time to do a leakdown test.

If you want to keep chasing the CIS, I'll sit down.

Peter,

I have the same thought. A lot of OIL is getting into the combustion chambers in all six (6) cylinders. Refurbishing the complete CIS for this motor will not prevent the smoking problem. A leak down test will tell us more where or what the culprit/s could be. It is surprising that you get the motor to start with all those fouled spark plugs.

Tony

[McGalliard]

One other thing I have not yet done is an oil change. In theory, maybe the last guy, who owned but did not really drive the car, topped it off but while cold and resulted in overfilling??? Wishful thinking I know, but I don't want to consider the prospects of engine rebuilds at this point.

I do not have the fuel cut off switch/plug on this model. That came post '75.

[Schulisco]

The one and only way to measure the oil level in an aircooled 911 is via the oil dipstick on a warmed up and idling engine with the car on an even flat surface ...

https://forums.pelicanparts.com/porsche-911-technical-forum/484679-1986-911-targa-oil-level-pressure.html#post4771356

https://www.youtube.com/watch?v=p_LjKjJEHNM

https://www.youtube.com/watch?v=mZPOb5TK9wY

[McGalliard]

Originally Posted by Schulisco

The one and only way to measure the oil level in an aircooled 911 is via the oil dipstick on a warmed up and idling engine with the car on an even flat surface ...

True. But I don't know if the prior owner knows that! That's my shot in the dark.

I particularly like the video of the guy describing a bag of extra blood at the hip, ready to use when needed.

[930cabman]

Originally Posted by McGalliard

One other thing I have not yet done is an oil change. In theory, maybe the last guy, who owned but did not really drive the car, topped it off but while cold and resulted in overfilling??? Wishful thinking I know, but I don't want to consider the prospects of engine rebuilds at this point.

I do not have the fuel cut off switch/plug on this model. That came post '75.

I would not want to see plugs looking like THAT. Have you tried a leakdown? I would start there, your CIS could be perfect, but if the rings/valve guides and out of spec, they must be repaired first

Oil level is checked with a warm, running engine on flat earth

[McGalliard]

We are (for the time being) pivoting away from the CIS and looking into engine health. Leak down (and maybe compression testing) is theoretically happening tonight/tomorrow. Will report back with the results.

Stay tuned…

[McGalliard]

For what it’s worth, the new plugs (out for leak down) are here. Probably less than an hour of operation time, little to none of which was extended high RPMs…

[ahh911]

McG,

The second spark plug from the top, honey on white porcelain. For me, there was a pinhole in the spark plug wire assembly below the dustboot. The car just wasn't running right, from cold start to hot. Just to warn you, I couldn't see a spark at night, close bench inspection caught the defect. Honey colored as well, looked exactly like yours.

Phil

[mike sampsel]

For what it's worth,
If I recall correctly, JW recommends leak downs done on warm engines. Maybe you can't do the warm one, did not read the entire thread.

[McGalliard]

Originally Posted by mike sampsel

For what it's worth,
If I recall correctly, JW recommends leak downs done on warm engines. Maybe you can't do the warm one, did not read the entire thread.

Now that you say that, I think you might be right. I recall seeing/hearing/reading a similar thing. I may do both for $%!@ and giggles.

[McGalliard]

Compression tests done today. All cylinders are at 150 psi +/- less than 5 psi.

I did reinvestigate the injectors and found at least one to not be atomizing well at all. Some of the others are questionable. So I think I’m going to replace the set.

[fanaudical]

Did you do a leakdown test too? Results?

Do the injectors start atomizing correctly if you lift the air metering plate? How do they look with the plate halfway up?

[McGalliard]

I haven’t done leak down because I’m not sure how best to access the crank shaft to position each piston for the test.

The injectors all fire with manual lifting of the plate. They atomize okay, as best I can tell through the hazy plastic wall of the graduated cylinders I have. But the patterns are a little questionable to me. I also don’t have a good means to know if the pressure point for opening is correct and within spec, hence the decision to just replace them.

[fanaudical]

What I've done for leakdown testing: Pull ALL the sparkplugs at once. I've been successful at squeezing the belt while rotating the fan pulley with a wrench (carefully!) and that's provide sufficient friction to turn the crank. A dowel in through the spark plug holes confirms the piston is at TDC.

[McGalliard]

Originally Posted by fanaudical

What I've done for leakdown testing: Pull ALL the sparkplugs at once. I've been successful at squeezing the belt while rotating the fan pulley with a wrench (carefully!) and that's provide sufficient friction to turn the crank. A dowel in through the spark plug holes confirms the piston is at TDC.

My plugs are already all out. That’s a good idea. I will try that. The dowel trick sounds slick! Now I just need a pulley wrench….

[PeteKz]

The crank pulley has marks 120 degrees apart that indicate when the pistons are at TDC. The remaining question is when each piston is at TDC at full compression. That will become obvious when you hook up the leakdown tester.

Next item: The leakdown test may not tell you where the oil is coming from. Specifically, if the intake valve guides or seals are leaking oil, you will measure more or less normal leakdown numbers. But let's see what the test shows.

[HarryD]

Originally Posted by McGalliard

My plugs are already all out. That’s a good idea. I will try that. The dowel trick sounds slick! Now I just need a pulley wrench….

The nut on the alternator is either a 22 or 24 mm.

[mikedsilva]

Limited experience here... a couple years ago, I bought a 3.2 engine to rebuild as a project.
I wanted to test run it first so I put it on my test stand... it started and ran 'well'. But after a couple minutes running, it would start to blow a LOT of white smoke.

The next day I started it cold... seemed perfect.. after it got a little heat into it, it blew more and more white smoke. It never cleared so I rebuilt it.

The machine shop found that the valve guides were SO worn, that the valves had so much movement in them, that the seats were concave. Pretty sure this was the source of my white smoke. New guides, new valves and new seats.

After the engine was rebuilt, it ran perfect and never blew smoke.

My understanding is that blue smoke is burnt oil and white smoke is unburnt oil. A bit like a plane signwriting in the sky... not sure if that's a good analogy.


On another engine I worked on, it blew white smoke when the engine got HOT. Turns out that the engine had been sitting for a LONG time and had also been overfilled.. so much that the muffler got oil into it. When the muffler got hot, it made the oil smoke... I changed to a known good muffler and the engine never blew smoke. So in the end, I tried to flush out the old muffler, and then I just ran it and ran it till all the oil was burned out of it!

[930cabman]

There are oil rings to keep things tidy, minimize oil leakage into the combustion chamber and there are compression rings to provide the pressure for combustion. A leakdown will ONLY test for the compression rings.

It's very possible the compression rings are ok, but the oil rings are clogged from overheating or excess contamination from dirty oil