Timing issue on AHU TDI.

Posting here because the car is now modded, but not sure that's really affecting anything.

Mods:
DLC1019's. Egr delete. K03 hybrid. Large front mount. Filter on a stick. 2.5" exhaust. Kerma tune for all of that.

Other relevant work done at the same time:
Timing belt. Excessive intake manifold and intake port cleaning. Engine has 135k according to odometer.

Ok. So before the work, the car ran ok. I was amazed it ran as well as it did considering all of the buildup in the intake and ports.

I did the timing belt by locking the pump with the pin, and releasing the can from the sprocket like you are supposed to. Nothing fought me on the job.

Started the car, ran ok even before I put the tune in. So I get the car warmed up, and go to set the pump timing.

Ok, for one the last few times I did this(different cars) once you switch to basic settings it runs kind of rough.. this thing barely runs. Chugs, backfires, etc. So question 1, not sure if this is normal on big injectors or maybe I just don't recall the last times as well as I think?

Moving on.. coolant temp at 85 degrees, vag com tells me "pump too far advanced to plot". So I shut down, removed all the intake piping so I can get the cover off and loosen the bolts. While doing that, verify that when the crank is at TDC the timing tool pin still slides easily into the pump bracket. Check, it does. So it's likely reasonable to assume the previous owner had the engine running with this kind of advance as well.
So with all the pump bolts loose except the one you can get to with the engine running, start it back up. Get the pump in range with a pry bar, and it's REALLY coughing and farting while in basic settings. Get out of basic settings and it runs like it seems it should. With the pump timing set, I do the hammer mod. Kerma instructions say 5.8. It was at like 1.5 with those injectors. After it changing every time I tightened the bolts I got it to 5.6 and called it good.

Shut the car off, go eat lunch. Come back, tighten all the pump bolts, remove the ic piping so I can reinstall the timing cover, reinstall piping, figure ok now I will install the chips.(this is a swap car, wanted to start it on stock program to isolate swap issues with chip issues).
Go to start the car. Just cranks and cranks and cranks. ECT now down to like 35 deg C.

Ok. Wth. Bad chips from Kerma? Pull the ecu, put stock chips back in. Same thing. You can probably crank it all day and it won't start.

So off comes the cooler piping and timing covers again. Also removed the valve cover to verify cam timing. Everything is good.

Long story short, the only way this thing wants to cold start(cold being 85-90 degrees out) is if the injection pump gets advanced back to it's as found location. That's easy to approximate, because retarding the pump enough to make vag com happy has me fighting the injector lines so hard I can't do it without a pry bar because it wants to spring back so bad.

So I guess what I am trying to figure out is what could be causing this? I have the pump somewhere inbetween right now. Still too far advanced to plot but not near as advanced as when I got the car. Cold cranking it, it takes about 7 seconds to fire, and another 5 to 6 to fire off fully and run. Then it seems fine. Runs strong.
At this point i think I ruled out pretty much anything I could have done wrong? Is it possible the previous owner was having a cold start issue due to some other issue and someone advanced the pump to make it run? Or somehow the pump found it's way this far advanced and did something to the engine where now it needs that much advance to run?
Or could i be missing something?

Oh yeah. No codes except for egr solenoid not present since I deleted the solenoid



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Video of a cold start.

https://youtu.be/DvV0bjeZPcE

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ive heard more than once that sometimes you have to set an AHU pump 1 tooth off in order to get a good range of movement for adjustments.

i would try that and see what happens when you put it in basic settings. if it runs less rough in basic settings when its 1 tooth off than it does now, you found your problem.

this hasnt been my personal experience, mine has always been on the "requested" line or above right from the start. im just lucky, LOL

easy enough to check though, right?

I'm not sure that would help. I can get the pump in range requested by the vag com, but when I do it refuses to cold start.
The other day, vagcom said I had the pump set dead in the middle. Took it for a ride, drove fantastic.
After it cooled off it refuses to start. The ecu isn't even turning on the glow plugs apparently because it's so warm out.
Only way to get it to start is to advance the pump

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I'm basically wondering if this is an indication the engine lost compression either due to age and the p.o. advanced the pump to make up for it, or if the p.o. had the belt or something else done, pump was set/left/whatever advanced because lack of a vagcom and damaged the engine where it won't run unless the pump timing is way advanced.
I have an old diesel tractor from the 60s that's apparently getting tired. Compression numbers are getting low, and when it's below 50 degrees F, the only way to get it to fire off is to run a heater on the intake a while to heat up the intake air..

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Have you checked while the engine is running if your damper pulley is woobling?
Also did you check you timing belt at the flywheel also?

For the crank reference marks, I have been using the flywheel mark. the (-) line per the bentley. Coincidentally it lines up with a paint mark on the crank that the previous owner made.

No wobbles.

And after driving the car ~6 miles, all marks line up(flywheel, pump sprocket hole to mounting flange hole), and cam cutout parallel with valve cover rail.

Well if everything lines up, i have no explanation for the car not holding normal idle in basic settings with the timing in the normal range.

Yeah, same here. Was figuring someone else might have some input.
The big deal is the refusal to fire off when its cold, and the pump in spec. With the pump real advanced(where I found it), fires off "ok". Where it is now, inbetween the two, takes a while but runs ok once it does.

IF the engine is having a compression issue, advancing the pump timing should theoretically make if fire off sooner, as it will build more heat in the chamber, correct?

Memory is getting a little foggy on personal experience with out of spec timing, but I seem to recall that if the pump is too far advanced the engine is going to run hot. Im wondering if its possible the previous owner just drove around with it advanced for a long time, and accelerated wear on parts, compression dropped, and now it needs that extra heat to get going.

There is no history available on the car, but it has been "messed with". Paint marker on all of the sprockets indicate a shade tree timing belt replacement where the cam was likely not even popped loose. And I didnt need a special socket for the hammer mod because the screw was already cut to accept a flat head screw driver.

BoostedOne said:

Yeah, same here. Was figuring someone else might have some input.
The big deal is the refusal to fire off when its cold, and the pump in spec. With the pump real advanced(where I found it), fires off "ok". Where it is now, inbetween the two, takes a while but runs ok once it does.
IF the engine is having a compression issue, advancing the pump timing should theoretically make if fire off sooner, as it will build more heat in the chamber, correct?
Memory is getting a little foggy on personal experience with out of spec timing, but I seem to recall that if the pump is too far advanced the engine is going to run hot. Im wondering if its possible the previous owner just drove around with it advanced for a long time, and accelerated wear on parts, compression dropped, and now it needs that extra heat to get going.
There is no history available on the car, but it has been "messed with". Paint marker on all of the sprockets indicate a shade tree timing belt replacement where the cam was likely not even popped loose. And I didnt need a special socket for the hammer mod because the screw was already cut to accept a flat head screw driver.

Click to expand...

It seems to me that when you put the pump timing to spec it get very retarded, i had an issue with afn block, ( Tdi110 ), but it was the crank sprocket that was bad, and the timing got so retarded that eventually it refused to start from cold.
Hammer mod i dont think is gonna solve anything related to the starting problem, because you already have bigger nozzlesm but one thing is certain, pump timing too retarded and you will suffer to start from cold.
I have had my Afn too far out of spec advanced for some time, and it never got hot.

Change the IQ to a lower number. Those instructions that come with the injectors are generic in nature and intended to maximize compatibility with stock, various tunes vendors, different cars and a variety of mods. In other words, low smoke settings. It will start better at a lower IQ number that's closer to the 3.0 or 2.5 area. There may be more smoke also.

I always say that the injector instructions are a starting point. When I'm asked "what number should I use", my answer is "it depends". The exact "number" will change with the individual car and the user's personal preference/tolerance for smoke. Adjust the IQ to get the most power while keeping the smoke tolerable. (e.g. tolerable may mean "no smoke") Finding "the number" will take a bit of trial and error. Some people are not comfortable with an answer like that, they WANT "a number". So what do you do in that situation, you go conservative.

Well.. this post is pretty old but FINALLY got the time to fix it yesterday.
At a VW meet last October I had the car and was mentioning this to a couple of friends. One of them said "The pump is way too retarded, the EDU is picking up on the wrong(the next) tooth on the wheel inside the pump. Advance the heck out of it until you start picking up the correct tooth." To which my other friend, who was there with his 3 day old AHU swap, agreed. Said he just did the exact same thing the night before.
The car is a project, being torn apart for a full respray all year so the pump wasn't high on the priority list. But paint day is drawing near, and I wanted to do it before I put on the paint(one less opportunity to knick it) so I did it yesterday.
Removed the intake tubing and timing cover and loosened the pump bolts and advanced the timing a tad and tightened the one bolt. About 65 degrees outside, it took about 15-20 seconds to start.
Once warmed up, got the vag com going and advanced to the point I was off the chart again then cranked even further and sure enough the crosshairs came back. Got it right in the middle. The tone of the engine didn't even change between being in basic settings or not but the glow plug light was blinking so it was definitely reading it.
Shut the car down, tightened the pump back up and put everything back together and rechecked the timing and still right in the middle.
Drove the car outside to wash it in prep of the bodywork and let it sit outside to dry while i went to town for things.
7hrs later get home and it's dark and about 45 or 50 degrees. Turn the key to move it back in the shop and it cranks maybe 3 revolutions and fires right up!

So someone mentioned that sometimes you might have to advance the sprocket a tooth. I imagine that is for the same reason. But I still think the sprocket should be right when the locking tool is in the hole. I suspect the last person who did the timing may not have used the locking tool and had the belt off a tooth, moved every thing to that location and locked it down and that's why it seemed like its happy place was so far off.
But either way, if you end up in this situation where it's barely running when you are getting in the ballpark of where vag com says and it only gets worse the closer you go, you might just need to advance it way further so the ecm picks up the next tooth in the pump.


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Just adding my experience for future reference, my modded up AHU always needs the pump gear advanced a tooth to get into the right window. I had the exact same struggles you were describing when I first tried running it.