Printable Version of Topic

Posted by: Vacca Rabite Feb 18 2018, 11:46 PM

https://www.youtube.com/watch?v=Ib4VMyWAwl8


Got Matt's car running this weekend after a few years down. 123 ignition installed and timed. Valves adjusted.

Car is a 1.7 with stock injection.

Its blowing prodigious amounts of white smoke when the engine is under load.

I did not check compression.

Matt assumes a vacuum leak, which is certainly possible.

Curious notes: all the valves were tight EXCEPT the valves for cylinder 3, which were in spec.

Okay brain trust. What'ca got?
Zach

Posted by: falcor75 Feb 18 2018, 11:53 PM

Was the engine properly hot when the smoke occurs?

-Old gas
-Oil in the exhaust/cylinders that needs to burn off (a few hours of driving)
-Worn valve guides and or piston rings.

Posted by: plays with cars Feb 19 2018, 01:21 AM

Usually on cars you have three choices for smoke color out of the tailpipe:
White - coolant in the combustion chamber
Blue - oil in the combustion chamber
Black - too much fuel in the combustion chamber

That sir was blue smoke. Mats nailed it on possible sources.

Posted by: Vacca Rabite Feb 19 2018, 08:06 AM

Old gas. I wonder how old the gas is in the tank. Possibly a few years old. Or New. I’ll find out.

Zach

Posted by: ericoneal Feb 19 2018, 08:59 AM

Mine was doing the exact same thing before a rebuild, was the rings. I also had large amounts of oil barfing out of the breather box on to the top of the engine when this happened. (crank case pressure?) May want to watch for that too...

Posted by: sithot Feb 19 2018, 09:14 AM

Once witnessed a 3.0SC that bent valves with a missed shift doing a similar thing as unburnt fuel went to vapor straight out the tailpipe.

From personal experience I had a fuel distributor in a '74 911 I owned develop a pin hole in the metering plate. Looked like a mosquito fogger. UNBURNT FUEL and some blue smoke.

Regarding sitting up for a while:

Years ago I bought a barn find BMW R69S. It has sat for a few years and while it cleaned up beautifully, it did not run.

The gas tank was a mess and I spent 2 weeks cleaning it. Care had to be exercised as the bike was a rare color and the paint was original. Used acid, nuts and bolts and a lot of neutralizer. It was re-coated with a PPG 2 part expoxy product I've had good luck with. FWIW, the coating is now over 15 year old and is still in perfect condition.

The engine had little compression. I loosened all the valves and took a dead blow hammer to the stems to knock off any debris/carbon/rust. Did a complete tune up (points, condenser, valve adjustment, oil change and brand new (now NLA) Bing carburetors.
Pumped 30 weight oil into the cylinders and spent about 15 minutes kicking it over. Re-checked compression and deemed it was enough to get it started. It did start and smoked like freight train while blowing out rust and other debris in the mufflers.

Next came the "Italian Tune Up". I had already decided to do a top-end if necessary but thought the bike deserved a chance. These are very robust machines.
I took it out and ran it up to redline (7,000+rpm) in 1st an 2nd and then cruised in 3rd for a cool down. This was repeated for about a half dozen times.
Rode back to the garage and dumped the oil. Re-filled the sump and rode it for an hour or so. It performed flawlessly.

To this day this bike is still one of the strongest running vintage BMWs I've ever ridden and I've had a few. FWIW: It's with a close friend who considers it one the best bikes in his collection of vintage BMW motorcycles.

AND IT DOES NOT SMOKE AT ALL

Posted by: Dave_Darling Feb 19 2018, 03:30 PM

Unburned fuel smells a lot like fuel. Burning oil smells different.

--DD

Posted by: sithot Feb 19 2018, 03:33 PM

No kidding? LOL

Posted by: saigon71 Feb 19 2018, 03:50 PM

I may have been the last one that helped Matt with his car before you Zach. That was several years ago.

Agree with checking on the age of the gas. Treat existing gas with Star-Tron, fill up with fresh gas and bang a can of Sea Foam in there as well.

Aside from the smoke, did it run well?

If so, I'd run it a little and see if things clear up before digging too deep.

Let me know if you guys need a hand with anything.

Posted by: Dave_Darling Feb 19 2018, 04:27 PM

Just pointing out that you can use your sense of smell to help figure out what is leaking...

If the cloud smells sweet like anti-freeze, something is really wrong with your 914!!!

--DD

Posted by: injunmort Feb 19 2018, 04:45 PM

fresh oil and filter? after years down there is bound to be condensation in the crankcase.

Posted by: Rand Feb 19 2018, 04:48 PM

That's blue, not white. White would be excess gas or water in the combustion system. Blue=oil. That's oil in the video.

Posted by: sithot Feb 19 2018, 04:52 PM

Ha!

Posted by: rgalla9146 Feb 19 2018, 09:00 PM

Did some teenage expert fix it up with Seafoam ?

Posted by: plas76targa Feb 20 2018, 06:33 AM

Unfortunately my senses for taste and smell died 10+ yrs ago. I count on trustworthy friends to comment on the aroma the cars exhaust.

I’ll add that there is oil all over the heat exchangers, most had burned off by time the video was made. I hope the new cork gaskets on valve covers stop further oil leaks or i’ll Have more to dig into and remedy.

Posted by: bulitt Feb 20 2018, 06:46 AM

Put the cigar out Zachery...

Posted by: Vacca Rabite Feb 20 2018, 07:46 AM

Bob, do you remember if you did Matt's valves? For the life of me I can't think of a reason why all the valves BUT the valves on Cyl3 would be tight. In all my experience, its the other way around.

The valves on CYL 1, 2, 4 were tight enough that I could not get a feeler gauge in there with the engine cold. Cyl 3 was perfect. It was like someone just did a valve adjustment on that cylinder.

I wish I had thought to do a compression check.

Zach

Posted by: Vacca Rabite Feb 20 2018, 07:54 AM

Woohoo! Matt showed up!

Theo was really jealous that I was at your house and he wasn't there. He made me promise to bring him next time.

When you have a chance, do a compression test at some point and check back in. This is a 2 person job, get Kath or one of the kids to help. If you have not done one before:
1) Run the engine till it is up to operating temp
2) pull the all spark plugs out (they will be hot - careful)
3) Put your foot on the thottle and open it wide.
4) crank the engine for a few seconds while someone reads the results on the compression tester. With the plugs out it will spin pretty easy. It may take several rotations for the compression tester to stabilize.
5) do it for all 4 cylinders, and write down the results.

If you don't have a tester, they can be rented from just about any parts store, or purchased from Harbor Freight.

I also have a leakdown tester that I will bring the next time I come over.
Compression testing checks peak compression. Leakdown lets you know how bad a leak is, and helps you find it (head leak, ring leak, etc.)


Zach

Posted by: saigon71 Feb 20 2018, 08:05 AM

Our focus was on setting the TPS when I was down. Matt mentioned that it had been a long time since his valves were adjusted, but we didn't have time to get to it.

Posted by: sithot Feb 20 2018, 08:39 AM

I'd dump the tank, adjust the valves and put in 5 gallons of VP or Sunoco Optima and beat it like a rented mule.

FWIW; the older air cooled 911's can smoke when they sit up a long time due to oil flowing back into the sump and finding it's way into the cylinders. Jeff Gamroth sells one way valves off the sump for this very reason.

Good luck.

YMMV

Posted by: Eric_Shea Feb 20 2018, 12:27 PM

Stuck or broken ring. Oil.

Posted by: Vacca Rabite Feb 20 2018, 08:05 PM

I've had that thought.
I'm hoping not.

I'm still hoping fresh gas and oil and an Italian tuneup will chase the smoke away.

Zach

Posted by: Dave_Darling Feb 21 2018, 12:04 PM

Don't forget to disable the fuel pump and/or the injectors. Fuel can come out of the spark plug holes at a pretty high velocity and make a big mess!!

--DD