Mechanical Timing off, but doesn’t make sense

The $180 DMF a few have noted from Amazon is a great DD clutch, but I don’t know if it’s TDC mark is right. I’m in the process of resetting mechanical timing on this B4 with one and the facts don’t make sense to me. This is what they are:

• IP and cam shaft are in-time with each other.
• Flywheel/crankshaft is 14 teeth behind the other two.
• VCDS reports N108 @ ~65% to have pump in time with the crank/flywheel.
• The 14 teeth is where I marked TDC on the flywheel due to where the cam and IP hit TDC themselves relative to a mechanical punch assumed to indicate TDC on the DMF flywheel.
• This measures out to ~37-38° which is inside of the +/- 55° lobe separation and I’ve confirmed no valve-piston contact, which makes sense, but moving the engine back and forth with the cam at TDC points to the mechanical mark as true.

Why was this engine able to run? Is the mechanical TDC mark off because of the different transmission housing the DMF (Luk 17-050) has a different viewport? What do I trust, the physical matching of the IP-cam, or the VCDS matching of the IP-crank which matches fuel injection from the 3rd injector to the timing output of the crank position sensor?

This occurred before and after resealing the IP, which I opted to do off the car. I know the history of the car with no hard starts and regular levels of smoke. I’ve been in VCDS before and after and I’m having a hard time understanding how the crank can be so far off and the car run normal.

My LuK RepSet 17-050 flywheel had a TDC mark that looked like this:




Perhaps the B4 viewing window is offset versus the A4?

Nope, not on this one. It's a divot like a center punch mark. I was thinking that the viewing window is different too, but the couple of manual A4's I've looked at under the hood didn't seem that way.

Wouldn't the valves and pistons meet at 14 teeth out?

You didn't compare TDC marks on the flywheels before you installed the new one?

Seatman said:

Wouldn't the valves and pistons meet at 14 teeth out?

Click to expand...

If the cam is kept in time with the crank, no. If the cam is stationary, yes.

turbodieseldyke said:

You didn't compare TDC marks on the flywheels before you installed the new one?

Click to expand...

Honestly don't remember from a couple of years ago. Went hunting for the other DMF that was previously in the car, but it's MIA. Even before firing it up, I spun the engine with a wrench and didn't have an issue.

Okay. Found the TDC mark with two additional marks that appeared to be indicator arrows. This TDC mark was a mechanical depression that differed from the previous photo, which matches a Sachs stock DMF, and is positioned and shaped such that during the daytime, it appears to be a shadow. Final count was 4-4.5 teeth of 132 teeth, or 10.9-12.3° off with the cam and IP advance, or crank retarded if you prefer.

Oh, and the other mechanical marks, there were 4 and they were not evenly spaced. I marked the TDC-neighboring starter ring gear teeth with a gold and silver paint pens.

The flywheel bolts are not equispaced on the PCD so it can only bolt on one way. When lining up with the Sachs unit removed from my Golf, the marks looked the same and were in the same spot.


My wife's (sold) NB had a flywheel with not one, but two TDC marks! JasonTDI found that one out the hard way when doing the timing belt. I rediscovered it when doing a pump replacement. The proper mark was made more prominent with a chisel and a paint marker.



Glad you found the TDC mark - you may consider the use of a chisel as marker can fade or come off with solvent or oil.

Well dredging up this old thread just might be my problem. I have the Luk 17-050 installed in my B4 but installed it when I put the 6 speed conversation kit in a few years ago so I never messed with the timing at that time and all was fine. Fast forward to last week and time for the 60k timing belt refresh along with a rebuilt injection pump from Cascade German and in spite of several timing mark verifications it is extremely hard starting. To the point that it will only light off with a little squirt of ether and then very smokey for a few minutes until warming up a little. Timing was initially set with a dial indicator as Bentley describes so the vcds basic settings graph is dead on in the center. I have been searching the forum for ideas and having verified and re-verified the timing belt parameters I'm still scratching my head. My next move was going to be verification of the timing mark of the flywheel which this thread questions the validity of, so feeling better about next moves now. As I recall the Luk 17-050 did not list the B4 as compatible and I assumed that the backing plate in the bellhousing interference was the reason for which a little trimming easily rectified. Guess the TDC mark may also be an issue. I will be pulling the #1 glow plug and with the dial indicator I will establish TDC and see if there is a mark in the bellhousing window. One other oddity I observed with vcds in basic settings the idle is very rough and the timing randomly jumps off the top of the graph showing a reading of 255 which some suggest might be a faulty connection in the pump wiring. Could that random brief max timing be the ecu trying to make sense and compensate for the angle of the dangle being off on the crankshaft position? Just thinking this through before changing anything. Any thoughts on the matter are appreciated.

Do those engines have a TDC dimple on the stamped steel timing belt cover such as the ALH does? 255 is as I recall the max timing when cycling the advance solenoid in vcds output test. I think I would run that output test just to see if the timing mechanism is doing a full sweep. IQ setting ok and stable

Because no one has mentioned it...

If one is using non-sanctioned parts on an engine (for reference, only used a 17-050 kit on my B4V years back and had zero issues) one can verify TDC by removing #1 glow plug and using a piece of wire as a depth gauge in the GP hole to the top of the piston. Roll the engine back and forth around TDC (or where you think it is), and watch the height of the wire. The high point will be hard to spot, so look for the mid point between two equal lower points (depths) on the wire. Helps immensely if you have one person on the crank and one person eyeballing the wire.

If you try the above, make sure the wire does not get pinched or caught on the cylinder by the piston, move the rod in and out of the GP hole slightly throughout to make sure it's not getting bent.

So I finally got the time today to verify TDC and the timing mark on the non-sanctioned 17-050 clutch/ flywheel kit. Used the #1 glow plug hole and a piece of wire to verify it's dead nuts on so back to the drawing board on my issue. I'll start another thread to keep this one on track.

Maybe try advancing or retarding the IP gear by one tooth.

-Todd

Have you inspected the crankshaft sprocket and bolt? If everything is aligning up correctly and your at "tdc" it has to be the sprocket. I know you " felt tdc with a wire" but there is enough slip on the system to be a little bit off on the crank side. The only way to ensure that you are at tdc is at the crank.

Okay just to review, it doesn't "have to be" the crank sprocket. Two things have been changed at the same time... the 60k timing belt replacement and and probably more related to the actual problem the injection pump was replaced with a rebuilt unit from a reputable supplier to our group of B4 enthusiasts. For the record the car ran perfectly before these 2 changes and I am comfortable with timing belt service having successfully completed this excercise a number of times. The only reason I decided to go with a rebuilt injection pump was that it was leaking (which I could have fixed with the reseal kit I have on the shelf) and the pump drive shaft had nearly 1/2" of lateral movement which would require complete disassembly to address. So I replaced a known working pump with one that has no track record since completely being gone through. It doesn't respond to timing adjustments as a normal pump does and after sending the video of the timing graph in vcds to Aaron at Cascade German and discussing the adjustments made and lack of any sensible results the rebuilt pump will be swapped out under warranty. I do appreciate the suggestion on the crank sprocket and that was on my radar for troubleshooting but not the problem this time.

I hate it when I change two or more things and all of a sudden there's a problem....that TBH shouldn't be there if everything was done right.

Steve