white smoke on startup

[BlueDog]

In this colder weather my Jetta smokes white smoke and runs rough when first started. Acts like it's running on three cylinders at first. I recently installed new rings about 750 miles ago. Once the motor warms up it smooths out (running on all four) and runs great with no smoke. Anyone have an idea what might be causing this or where I should start checking first?

[82vdub]

poor combusion, low compression, incorrect timing, fuel issues, bad injector spray patterns and a few other items cause incomplete fuel combustion that is the smoke you see. Part of the equation on how well fuel combusts is the temperature of the cylinder. You can tweak the timing to see if it goes away in the winter months and try to adjust a few of the other items to try to make it go away, but it may not ever go away until all items are properly addressed. Ole 82 coughs and bucks and smokes bad for 30 seconds when it's this cold out, but goes away relatively quickly.

[Fatmobile]

Air in the fuel can cause white smoke.
Get clear fuel lines to and from the pump.
Also advance the timing a little.
How does pulling the cold start knob effect things.

[BlueDog]

I suspect poor combustion in one way or another. Timing is right on, injectors were rebuilt and tuned about a year ago and didn't change the smoke issue last winter, I have run clear fuel lines for many years now and pulling out the cold start doesn't change the smoke. When it's 40 degrees out it produces white smoke for about 20 to 30 seconds, the fourth cylinder begins to fire and runs smooth and smoke goes away. When it's really cold, 15 degrees like yesterday, it produces white smoke for about 2 minutes before the fourth cylinder begins to fire and runs smooth and the smoke goes away. Since it has brand new rings I suspect I may have a problem with valves on one cylinder. I does't seem like valves would be affected by cold temps.

[TylerDurden]

Hydraulic or mechanical lifters?

[Fatmobile]

How are the glow plugs working? Asking because one cylinder is acting funny at first.
Block heater change how it starts?
Clear lines where? To and from the pump?

[BlueDog]

The lifters are hydraulic.

All four glow plugs are working well.

Ran the block heater this morning for 45 minutes. Engine started on all four cylinders and absolutely no smoke.

I have clear lines going into the injection pump but not on the exit.

[greg lousy]

All four glow plugs are working well.

Ran the block heater this morning for 45 minutes. Engine started on all four cylinders and absolutely no smoke

... visual inspection of glow plugs?.... the difference in starting w/ block heater plugged in points to glow plugs.

[BlueDog]

Each of the glow plugs glow red hot.

[greg lousy]

did you look at the plugs installed with injectors removed?
have you tried swapping the # 4 injector with another one to see if the problem moves with it?

personally, i would do those two things (in the same procedure), then move on to compression test if I still had no answer

[BlueDog]

No I haven't. Why would a glow plug act differently when installed than what it does uninstalled?

BTW, I can manually operate the glow plugs and it appears to significantly shorten the time that the engine smokes.

[greg lousy]

They probably wouldn't, but I like to look at them installed because it also tests the circuit and the relay (which it sounds like you've bypassed )
With one underachieving cylinder, I would rule out (or not) the injector by swapping positions and while I'm in there I'd take the opportunity to look at the plugs and see, 100%, how the glow system is working.


I've also got a manual glow plug button and I often use the plugs when its really cold after the engine starts, definitely smooths out warm up
. ... once referred to here as "manual afterglow"

[Fatmobile]

The lifters are hydraulic.

All four glow plugs are working well.

Ran the block heater this morning for 45 minutes. Engine started on all four cylinders and absolutely no smoke.

I have clear lines going into the injection pump but not on the exit.

How many amps are the glow plugs pulling after they warm up? Or how did you test them?
Get a clear line coming from the pump. Even though the block heater test indicates it's not a fuel syphoning back to the tank problem.

How does pulling the cold start lever effect sound and roughness of idle when started cold.
I suspect your timing might be a little retarded and the block heater makes it more tolerant.
When it misses it's not random? It sounds like it's always one cylinder?