17656- P1248 Advanced Timing out of nowhere

2000 VW Jetta TDI Auto. 220000kms.

Changed the timing belt 3000kms ago. Tweaked the timing with VCDS and it's been running like a top.

Driving it yesterday, timing sounded like it was advanced (rattly). Not great power....not much until I stepped on it then it would take off.

Rattly seemed to go away above 2200rpm.

Ran VagCom and got P1248 Start of Injection Timing - Control Deviation- Intermittent.

TDI Timing shows a vertical yellow line as way to far advanced.

Adjusted the fuel pump sprocket as far retarded as I could get it.

Still getting P1248 that I can't clear and the vertical line on TDI timing.

Not sure what's going on. Filled it up about 300km ago. Could a bad tank of fuel do this? Ran 2 cans of Diesel Purge through it with no change.

If I pull fuse 34 the timing really advances, showing me that N108 is working I believe.

Any ideas? I'm at a bit of a loss.

Is the belt tension still very tight?? If everything checks out (including crank sprocket and cam sprocket not having slipped) in the belt/fixture department, then it could be internal pump issue. I would check closely for cam sprocket movement. Fuel not the issue.

Roll the engine manually to TDC on the crank, see if your pump pin hole is aligned. I'd say check the camlock but you have to pull the vacuum pump to do that and it WILL seep oil if the gasket is not replaced, so either get a gasket or start with the crank and IP.

If alignment is off, even a bit, you got problems under that cover.

Checked the physical timing. Dead on.
Exercised n108 with output tests in vcds. Seemed to work.
Cleared codes and everything was back to normal....until this morning.
Now it's throwing the code again....now what?

Trace all your IP wiring. Could have a compromised wire (or two). Could be that your quantity adjuster is gunked up. What's the background on this car?

Car has been owned by my father for the past 8 years. I did fill the tank with some 1.5 year old diesel about 300kms before it started doing this...not sure if fuel has anything to do with it. I topped up the tank with fresh diesel and put in a healthy dose of fuel conditioner as well.

I was thinking that maybe your QA is gunked up by bad fuel/sitting.

From http://wiki.ross-tech.com/wiki/index.php/17656/P1248/004680

17656/P1248/004680 - Start of Injection Timing Regulation: Control Deviation

Possible Symptoms

• Loss of Power at high Engine Speeds
• Engine difficult to Start

Possible Causes

• Start of Injection Timing Regulation not OK
• Injection Pump Control Range blocked/dirty (e.g. by Metal Particles)
• Engine has stalled / ran out of Fuel recently
• Wiring/Connectors from/to Injection Valve (N108) faulty

Possible Solutions

• Check/Adjust Injection Start. See TDI Timing Checker
• Check Fuel Supply
• Check/Replace Fuse(s)
• Check/Repair Wiring/Connectors from/to Injection Valve (N108)
  • Run Output Tests

Special Notes

• Might by stored with other codes like 17654/P1246/004678.
• When stored in the VW (9M/1J) Golf/Jetta or (1C) Beetle with the ALH engine code Tech Tip 23-02-03 may be helpful. The summary involves removing power at idle to the N108 Cold Start Injection Valve (Fuse 34 on those body styles) while monitoring Basic Setting group 000.2 which is shown under "Timing" when using the TDI Timing Checker. When power is removed from N108 the live reading should change to 255.

dtreid said:

Car has been owned by my father for the past 8 years. I did fill the tank with some 1.5 year old diesel about 300kms before it started doing this...not sure if fuel has anything to do with it. I topped up the tank with fresh diesel and put in a healthy dose of fuel conditioner as well.

Click to expand...

Might be an excellent time for a LiquiMoly Diesel Purge treatment.

I ran 2 cans of diesel purge through it already.
Mucked around with it again this evening. Seems like after cycling the n108 valve with vcds, it seemed like the timing got back to normal.
I took it for a couple of hard 4500rpm runs and it was still holding the timing.

We'll see what happens to it tomorrow.

Sounds like an intermittent fault in the n108 or something to me.

Code is back. This is super annoying!

Seems that if I cycle the n108 with vcds output tests and by pulling fuse 34 I can get the car back to normal for a short period of time. So it would seem that the n108 is sticky. Is there a chance this will clear itself up with a good dose of diesel cleaner or should I be looking for a new n108?

I'll be monitoring this. Have a similar issue I posted about today. Changed the beLt like u said everything was running fine. Then loud engine and loss of power. I don't have the vag com to troubleshoot as far as u have. I'm no expert but in my troubleshooting I found the 3 wires on the grey connector chaffed. May be causing that I'm not sure. Wire repair didn't fix my issue. Good luck.

So I'm still getting the code and limp mode pretty much every time I drive it after a few minutes. Am I best just to replace the N108?

dtreid said:

Am I best just to replace the N108?

Click to expand...

Well, the default failure mode of the N108 valve is open...and the result is timing stuck at full advance. However, it could be the advance piston in the pump is sticking too.

The N108 valve is an expensive little bugger. DBWLLC sells them, and there's a nice how-to PDF linked on their page below.

http://www.dbwllc.net/product/028906283m-n108-injection-pump-advance-solenoid/

If the mileage is high, I think I'd be more inclined to swap the whole pump.

QA really has nothing to do with timing, but you can pull the QA and check the little ring magnet underneath.... ANY metal shavings sticking to this magnet and it's pump time ... also twice now i've seen a timing piston lose a chunk of metal that wedges itself between the piston and cover plate thus holding timing in the advanced position and causing this code ... could also be metal debris between the timing piston and it's bore causing sticking .... most metal debris in these pumps is ferrous and comes from worn drove lugs and/or cam plate/rollers ... as stated above ^^ electrical could also be an issue, so check wires from pump connector to pump especially those that run to the n108 which requres pump removal to access ... good luck !

My son's ALH Jetta has a dying inj pump (ticking)....metal particles caused the timing plunger to stick almost constantly when we got it over a year ago. I removed the front cover over the advance plunger bore where the return spring lives....found all of the particles there. Until we change out the inj pump this spring, I have replaced the timing plunger return spring with a piece of copper pipe to keep the timing constant. I had to pick a sweet spot...starts and idles without being too loud, but still gets decent fuel economy.

Funny thing to me is that the metal particles do NOT stick to a magnet.

We have our fingers crossed that the inj pump will hold together till this Spring when we can do timing belt and inj pump swap at the same time.

Good luck.

rallywagon said:

Funny thing to me is that the metal particles do NOT stick to a magnet.

Click to expand...

Aluminum does not stick to magnets.

...But none of the moving parts or wear parts are aluminum. Only the case?

wonneber said:

Aluminum does not stick to magnets.

Click to expand...

Neither do stainless or many alloys.

OP, call Mark at DFIS Portland to price out a replacement N108 solenoid/valve. I believe I was quoted a significantly less price than DBW's.

Dtreid, did you end up replacing the N108 or the whole pump?

My 02 Jetta wagon with 203k miles just threw the P1248 code.
Noticed it suddenly started idling rough / loud.
Pulling the fuse does change the idle.
I'm not in limp mode, but notice an abrupt change to a more normal sounding acceleration at 1950rpm.

Guess I'll take the pump off and have a look for debris. Though I'd like to know what you ended up doing as it sounds like it likely is the same issue.

Here's a good test to run using VCDS for this issue.

With the engine idling, login to the engine computer using VCDS, go to basic settings. Enter 04, click Go!

The computer will vary the duty cycle with the goal of reaching two different timing presets: "early" and "late".

From my watching this test on many cars, the approximate timing advance targets appears to be 4 degrees BTDC for "Late" and 8 degrees BTDC for "Early". Both are more advanced than what the engine normally runs at idle, but this is just a test of the timing advance system.

Running it can let you know is the timing advance working at all or did it somehow become stuck in an overadvanced position. I've had one pump where it out of blue went way overadvanced and even showed as being that way in basic setting 000, which shuts the n108 off altogether so you can check the pump's base timing.

I mechanically adjusted the pump back to spec, then ran basic setting 004 to see how well it was working and it did advance the timing, but got stuck again, and running basic setting 000 revealed the base timing was once again in a different position. That led me to believe either the n108 was sticking or the piston itself.

After removing the pump and disassembling, it became clear it was the piston. A chunk of it had broken off and disappeared into the ether. Strangely, the piece that was broken off was approximately inline with the orifice from the advance solenoid to move the piston against the spring that's behind it. I actually had a used pump body I had used the 11 mm guts out of, but still had a good timing piston in it. I swapped the customer's 10 mm guts into that pump body with new seals, put it back on the car, and this time the basic setting 04 test ran normal.

More often than not, I get cars that simply don't advance the timing at all beyond the base timing of the pump. Stays stuck wherever the base timing is set (0 to 2 degrees on average). The basic setting 04 test yields little or no advancement at all. More often than not when I encounter that, it is fixed by checking the case pressure relief valve. But not only tapping the collar back in place, but more importantly replacing the o rings on the valve. The lower o ring in particular at their age is very prone to become flattened and VERY hardened. Put new o rings on the valve, put the collar back flush, reinstall it into the pump, restart the car and recheck basic setting 04 again and more often than not the timing advance magically is working the way it's supposed to again.

Matt, thanks for this info! Swapping the case of an IP...major job...your customers are lucky to have you.

Do you know part numbers or dimensions of the o-rings on the relief valve?

Thanks.

rallywagon said:

...But none of the moving parts or wear parts are aluminum. Only the case?

Click to expand...

timing piston is an alloy of aluminum