Mk3 AHU cold start issues

Hey there,
So I changed my timing belt this weekend, not my first change for a TDI, but my first for this motor. The change went pretty well, (much easier than the ALH) I only used a socket to lock the fuel pump and the flat steel plate for the cam lock which is all I used for the ALH before. once back together car sputtered a little which I kinda expected but then ran fine, the next day it was a nightmare to get started from cold, it was also making lots of white smoke. Once I finally got it up to temp I adjusted the fuel timing and got it right on the green line (it was between the blue and red). The next night there wasn't even a chance at getting it started cold, but still lots of white smoke.. The glow plugs wernt coming staying on at all but it was also 70 degrees out...
Before I go tearing it all back down to verify that my crank and cam are lined up does anyone have any other suggestions? I feel like its timing since it only started after I did the change, but I also find it weird that it runs fine once started and starts fine once warm. Only error VCDS is giving me it glow plug intermittent. Next thing I was going to check was the 109 relay.. I had that happen to me on the MK4.

Follow up: I rechecked the timing, cam was a little behind. Fixed it and no Improvement, after getting it started I rechecked injector timing then checked injector output and noticed that injector 4 was blank nodding reading from it. All others were normal.. I cracked each line to make sure something was coming out of each one and to see if it affected idle and each one did.. still stumped on this one..

Normal reading*

The #3 injector is the reference, it is always "0.00". The ECU lists 1,2,4 as 1,2,3 just to confuse you. The +/- values are showing the difference between that injector and #3.

Doesn't solve your problem but eliminates a symptom.

Sent from my XT1097 using Tapatalk

Glow plug intermittent is your major clue. The second clue is it starts fine when warm. The white smoke is unburnt fuel. Check the glow plugs and the harness for voltage. I'm guessing the harness is not delivering voltage to the plugs. Wingnut has an excellent tutorial on testing and repairing the glow plug system.

RabbitGTI said:

Glow plug intermittent is your major clue. The second clue is it starts fine when warm. The white smoke is unburnt fuel. Check the glow plugs and the harness for voltage. I'm guessing the harness is not delivering voltage to the plugs. Wingnut has an excellent tutorial on testing and repairing the glow plug system.

Click to expand...

yeah the harness looks trashed, all the rubber is crumbled, but would that really create it issue if its 70 degrees out? I thought they really only did something if it was like sub 40 degrees, but then again im not as familiar with the older models.. but I do notice that it has a better chance when I flip the key a few times..

I didn't see FL. When you said cold start, I thought of cold weather. Should not make that much difference above 40 degrees as you say.

Try advancing just the pump 1 tooth. Many of us had needed to do this.

-Todd

Yeahbut he said he got it on the green line. Advancing the pump is required sometimes when it isn't on the graph at all.

Does sound like late timing though.

I seem to recall that the timing can essentially "circle around" if it's way too far out, appearing on the graph again after it has dropped off the bottom or gone off the top. Could be what is happening here.

Agree it sounds like retarded timing.

Sent from my XT1097 using Tapatalk

Never heard of it doing that. It will say too advanced to plot when it's actually retarded. Or maybe the other way around.

Did you do anything else during this job? Maybe disconnect the fuel filter?

It doesn't seem to be fueling issue since he's getting white smoke at the tailpipe.

I'd probably just reverify everything, at this point. Maybe jump the IP one tooth from the start.

-Todd

When car is cold verify fuel temp sensor is correct.

OK I'll check the sensors, one glow plug is shot, I increased the glow plug duration. Seems like it needs the plug to heat no matter what temp it is outside.

Yeahbut air in the lines might cause late timing and the attendant white smoke.

KLXD said:

Yeahbut air in the lines might cause late timing and the attendant white smoke.

Click to expand...

I think you're right, finally got to drive it around and when downshifting or gearing down I lose throttle response and have to push in the clutch to get the throttle back

What did you do to get it started?

You seeing air in the IP supply line? With a new filter and oring, I was seeing air. I used a larger oring and all was good.

-Todd

with all that work you havent stated you put in a new filter, and easy suggestion try a new air filter at the same time, dont forget to prime filter, and its from the inlet side(of filter). i ve heard of problems getting air out of filter, id guess its going to be because of a leak, possible main seal of pump is shot.? or trace down air leak/infiltration of fuel system.

ToddA1 said:

Try advancing just the pump 1 tooth. Many of us had needed to do this.

-Todd

Click to expand...

If I would have taken your advice from the beginning it would have saved me some major headache... It WAS off a tooth. It was so strange how VCDS was reading the injector timing right before though. After not only dealing with hard starts I was experiencing no throttle response after downshifting or even gearing down I went back to check the timing and this time it wasn't even on the charts, saying it was too advanced, but I knew that was wrong because if I tilted the IP back any further it would stall. I bumped it a tooth, which was surprisingly easy. I did however wreck the end of my cam by starting the motor with the cam lock still on Its ok, but I'm sure ill be throwing a fit if I ever have to change the TB on this again...

This is the first I've read of the indication being actually on the graph but being retarded.

I have seen similar instances when the crank sprocket is moving. I'm betting the crank sprocket is walking and setting the timing advanced means it's actually on.

It's easy to check by setting all the locks in place, or at least the cam and IP locks and verifying the flywheel is exact. I just had to do one of these last week and the crank sprocket moved.

So im back again with issues lol my injector timing keeps going retarded and im nearly certain is from the taper on the cam sprocket because it is a gradual change in timing. I was in a pinch at work hearing the valves start to chatter so I popped the cam sprocket counter clockwise and it fixed it enough to get it home. once back I took the sprocket off light sanded it, cleaned it, put green locktite on it (I know, nut im desperate at this point..) and put it back on tight! it seemed to hold for a few days but I had a hard start this morning so I think its going back.. Is there anything it could be? if it jumped a tooth im thinking it would change the timing the opposite direction.. Maybe I just need a new cam and sprocket.. idk

So im back again with issues lol my injector timing keeps going retarded and im nearly certain is from the taper on the cam sprocket because it is a gradual change in timing. I was in a pinch at work hearing the valves start to chatter so I popped the cam sprocket counter clockwise and it fixed it enough to get it home. once back I took the sprocket off light sanded it, cleaned it, put green locktite on it (I know, but im desperate at this point..) and put it back on tight! it seemed to hold for a few days but I had a hard start this morning so I think its going back.. Is there anything it could be? if it jumped a tooth im thinking it would change the timing the opposite direction.. Maybe I just need a new cam and sprocket.. idk

Look at Abacus' last post. Seems a likely thing to check.

Abacus said:

I have seen similar instances when the crank sprocket is moving. I'm betting the crank sprocket is walking and setting the timing advanced means it's actually on.

It's easy to check by setting all the locks in place, or at least the cam and IP locks and verifying the flywheel is exact. I just had to do one of these last week and the crank sprocket moved.

Click to expand...

What do you do to stop it from walking?

Replace the sprocket and bolt to start. Hopefully the crank isn't damaged. The longer you drive it like this the greater the chances of the crank snout being trashed.

Sent from my XT1097 using Tapatalk

Abacus said:

I have seen similar instances when the crank sprocket is moving. I'm betting the crank sprocket is walking and setting the timing advanced means it's actually on.

It's easy to check by setting all the locks in place, or at least the cam and IP locks and verifying the flywheel is exact. I just had to do one of these last week and the crank sprocket moved.

Click to expand...

That was it! Let me see if I can get a pic up to show how bad it was.

Wow! What's the crank look like?

Didn't reread the whole thread. Did you have the sprocket off for your belt change? And if so did you use a new bolt oiled and tightened to the correct torque plus a quarter turn?

And I hope it never moved enough for valve contact before you corrected it? Maybe lifter inspection is indicated?

How about downsizing the picher a little?

KLXD said:

Wow! What's the crank look like?

Didn't reread the whole thread. Did you have the sprocket off for your belt change? And if so did you use a new bolt oiled and tightened to the correct torque plus a quarter turn?

And I hope it never moved enough for valve contact before you corrected it? Maybe lifter inspection is indicated?

How about downsizing the picher a little?

Click to expand...

I did not take it off when I did the change, if I did it would have saved me from messing with the timing like 6 times lol. I didnt change the bolt because I was in a pinch to fix this and it was going to take a lot longer to get the bolt, I can always change it later pretty easily.
The Crank shaft looks alright, a little dinged up on the left corner where it dug into the sprocket. I should have known it was this much sooner because the serpentine belt was bouncing like crazy due to the gear being way off center.

I think the valves are ok, I had to re adjust the timing many times before fixing this and the car would have really bad cold starts and throttle response well before I had and valve chatter (although one morning I did hear them slightly so I fixed the timing in the parking lot as soon as I noticed)

Sorry about the Pic size, I thought it would be helpful for others too see how bad they can get, and this one only has 200k on it.