Found Cause for 2-3 minute Smoke at statup, now how do I fix it?

[ivanuf]

After reading all post that I could find about smoke at statup and getting a good idea of the possible causes (check valve 9mm ball, turbo seals, valve guides, etc..) none of these situations seem to be similar to mine.

My car smoked when cold (meaning left un-used for 4+ hours, temperature in PR is almost constant 85-90 degrees F). It only smoked at start up and not a puff of a couple of seconds. It smoked for 2-3 minutes. Once I drove off and the smoked cleared after 2-3 minutes there was no more smoke and it runs like a ball out of hell.

Stop for a short time, start the car again and no smoke. But leave It a couple of hours and again, startup smoke cloud for a couple of minutes.

Today I got it out for a morning run, and once it got warmed and smoke free I parked the car and proceeded to remove the scavager pump hose from the catch can (non-stock) and let it drained on a plastic container. (It was HOT!!) After one minute the entire content of the can was drained and also some from the hose. (See picture attached.) I marked this oil level as HOT in the pic. Then I proceed to leave to drain all day and you can see what happened in the picture, the oil keept filling the container drop by drop very slowly but not from the can (check valve and 9mm ball working) it was from the scaveger pump hose.

It drained close to 1 qt. Of oil. In a 4 hr. Period. After this I connected the hose again to the can, started the car and NO MORE SMOKE at start up.

So this is the source of the oil, now how do I stop the scavager pump from draining into the oil catch can and back into the Turbo? The car is a 77 non- intercooled. Is there a check valve after the scavager pump that I am missing or left out after the engine refresh?

I never read any situation like this on the smoke/ mosquito fogger posts of other members, any help from others members apreciated.

[boosted79]

What is your oil level in the oil tank when warm? The return line from the scavenge pump inside the tank is supposed to go up inside the tank so the end is above the oil level so oil cannot drain back through the pump into the can and the turbo. At least that's my understanding and if I remember correctly that's the way it is on my '79.

[ivanuf]

The oil level is 1/3 above the MIN. And 2/3 below the MAX. Range marks on the dipstick when fully warm. The oil return line is conected to the tank
At the bottom of the tank in my car. So I guess that the oil pressure back
To the turbo from the weight of the oil also contributes.

[boosted79]

You're not following me. The line INSIDE the tank goes up above the oil level to prevent drain back. My '79 has two fittings, one ends right inside the connection, the other one continues up. The one that terminates at the bottom of the tank can be used to return oil to the tank from an air-oil separator. The other one is used for scavenge return. I don't remember which is which because I don't use either of them. I dump the scavenge return into the breather housing on the engine and I drain my AOS manually. Does your tank have one or two fittings?

[ivanuf]

No I did not followed you on your 1st reply. Thanks for the clarification. My oil tank has only one fitting for oil return as shown on the picture. It is located about were I placed the red mark on the attached diagram.

Where exactyl is the one above the oil? It will have to be in the side on the tank inside the wheel? Any pics?



I ordered a 1/2” Moroso check valve from summit, to solve this, but I will prefer to solve it as the factory intended.

Ivan

[ivanuf]

After doing some research and following boosted 79 comments, the cause of my problem is that I do not have the proper oil tank and my scavager pump is not draining at the top of the tank. The solution will be to get a tank like the one in the picture below that like boosted 79 explained to me has a port that drains on top of the oil level and avoids the problem I am having.

For now I will put the check valve until I replace the tank.

Thanks

[boosted79]

Unless you are a "has to be stock" type of owner I'd just use the check valve and not bother with a different tank.

[smurfbus]

There might still be some confusion? Boosted said the bung at the bottom of the tank where I think yours is correctly connected goes up VIA a tube INSIDE the tank and effectively ends over the oil level. I might remember this wrong but this is how I understand it works.

Why yours is draining back is a mystery. You could try to drain some oil to get it at the min level and test. Did you check the level engine idling?

[boosted79]

His port might be for the drain from the air-oil separator, which would not extend up inside the tank. The only way to find out is drain the tank and see what happens inside the tank connection.

[1979-930]

Or pull the line next time he changes the oil to see how much if any comes out.


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[ivanuf]

I am sure that the port on my tank is not draining above the oil. I am waiting for the check valve to install. I will confirm that it worked once installed and post a couple of pictures. If the correct tank pops up at the classifieds at a reasonable price , I might get it just to put it back the way it was supposed to be. Thanks for the help solving this mystery.

[ivanuf]

Confirmed, smoked gone. Solved with check valve for now until I source a proper turbo tank.

Thanks for the help
Ivan