Bear
Veteran Member
- Joined
- Jun 23, 2003
- Location
- Westminster, Maryland
- TDI
- Golf GL 2 dr 2003 Mojave Beige, ESP, CWP, Monsoon, 2003.5 console
About a month ago, fivestring and I played around almost all weekend "fixing" a N108 valve to get rid of a 1269 code and restore his car's performance. This story is about the trials and tribulations of that fateful weekend. It was a wild ride to say the least. Unfortunately, there was little information available anywhere, including here or in the Bentley concerning the diagnosis of this particular problem. I am really surprised about Bentley, its the better part of $100 after all!
The moral of this story is: CHECK YOUR TIMING!
Here is how the weekend went. We confirmed that the car wasn't running right: not much power and the 1269 code. It seemed like it was making more of a diesel "rap" than normal but it was hard to tell for sure, especially at idle.
First, we spent an hour or so dinking around under the premise of getting the N108 out without taking the injection pump out. No way. There are two bolts holding it in. We decided the injection pump was coming out.
And out it came! Actually, it was not too bad taking it out. We did have the bent wrench and that helped a lot. It was a bit strange the way the bolts went through the pulley and the bolt holders, but it went really well. The pump needs to be "wiggled" just right and it comes right out. Wiggling it just right can take some patience though. Then we looked at the N108, took the bolts out, and then tried to get it out.
It wouldn't budge.
We looked it over and then decided to use a screwdriver and a hammer to tap on the "ears" of the N108. We did that and also sprayed penetrant liberally. After a while we could see that we were bending the ears on the N108, so we quit. This was after about a half hour of tapping. After a break, we resumed and kept it up. After about an hour we could see that we moved the N108 about 0.010". Success! Then we upped the ante a bit by putting some vise grips on the metal ears and rocking it. We could only turn it a few degrees with the vise grip. The routine was turn, turn, tap, tap for about another hour. Then we used one of my secret weapons for loosening stuff without a torch - we poured boiling water on it. That helped a good bit and we could then turn it at will and the taps became more productive. We had it out about fifteen minutes later. It was pretty ugly after being beat upon for over two hours.
Much to our surprise the N108 screen was clean, as was the orifice it sat in. We were pretty puzzled as we felt sure that it would have been plugged. At this point we decided to test the N108 to see if it would do anything.
Naturally, Bentley didn't tell us what voltage drove the thing. We were able to measure some resistance across the terminals but so what? We wanted to know if it actually worked. So we played around thinking that if we drove it with voltage, "something" would happen. A click, or something. Thinking that the N108 might be driven by 5 volts or so we rigged up some batteries and hooked them up but no response. We then tried 12V and voila! We were able to get an audible click. We then placed a small hose over the "tube" part of the N108 and we pumped it up to 25 psi with an air pump. We monitored the pressure gauge for a couple of minutes and guess what? It held gas pressure! BTW we were "driving" the gas flow the opposite way from how the fuel flows through the thing. No biggy. If the valve holds gas pressure it will sure as heck hold fuel back (remember liquids have viscosity values of about a million times more than gases). We then energized the valve and the gas pressure was relieved. We repeated this a number of times. We decided that the N108 was OK, so we put it back. BTW fivestring had new O-rings for the N108 and the inner one - having the correct p/n on the package - was in fact the wrong size so we reused the old one.
We then checked the timing using the normal method: put the pump pin in place, crank at TDC, etc., etc. We put the timing belt back on, hooked everything up and went for a ride and guess what?
It ran the same friggin' way as when we started! And threw the same code! Of course, this made sense as we didn't really CHANGE anything. We did waste about 30 man-hours though....
So, at 5PM on a Sunday... we looked at the VAG-com timing and sure enough, requested timing was 1.5 degrees BTDC and actual was 6.5 degrees BTDC. N108 duty cycle was about 70% (I believe... I am typing all this from memory). So, we figured that maybe the timing was off more than the N108 could compensate for. So much for it being a "cold start" injector. Its a timing device thats needed all the time, evidently.
Since the timing was more advanced than requested we loosened the pump bolts and pulled the pump housing in the direction of rotation (clock-wise looking at the engine from the passeneger side to the driver's side). Said another way, this was like pulling the top of the pump toward the front of the car. We were able to put a socket wrench through the pump pulley just by taking the TB cover off which saved time.
We started it up and whamo! Smoke all over the place and a horrible knock. Timing was now at something like 1.5 BTDC requested and 18.5 BTDC actual. So, we repeated the process and pushed the thing back the other way - toward the back of the car and guess what.... it now ran like a dream!!!!!
Timing requested and actual matched. N108 duty cycle percentage was down to around 40%. We went for a ride and it ran strong and quiet with no CEL.
Moral of the story. Check the timing. Lessons: BTDC to VAG-com must mean "beyond" TDC and not "before" TDC. Strange. The other thing I noticed is that the injection pump housing setting procedure is discussed in the injection pump part of the A3 Bentley and not in the timing belt section where it would seem to rightly belong.
Here is my take on what is going on with the N108 problems. Its a timing issue and related to timing belt replacement. The timing belt replacement procedure requires that the injection pump pulley and the crankshaft be locked down. The belt is then placed on and tightened. The problem is that there is no way to put tension on the timing belt in between the crank pulley and the injection pump pulley - they are fixed! So what happens is that all of the initial belt tension is around only a portion of the belt: from the crank pulley clockwise around to the injection pump pulley. When the car is started and the belt tension equalized then the injection pump timing naturally becomes slightly retarded from where it was (the distance along the belt path from the crank pulley to the injection pump pulley increases as the belt gets pulled harder).
I think that the timing belt procedure should be changed to incorporate injection pump setting. One way to do it would be to loosen the injection pump and move it forward to a retarded position before the belt is tightened at every timing belt replacement. That way, it would give you plenty of room on the slots to move the injection pump to the advanced direction (based on N108 duty and/or timing results from VAG-com).
Long one... sorry folks. Any comments???
The moral of this story is: CHECK YOUR TIMING!
Here is how the weekend went. We confirmed that the car wasn't running right: not much power and the 1269 code. It seemed like it was making more of a diesel "rap" than normal but it was hard to tell for sure, especially at idle.
First, we spent an hour or so dinking around under the premise of getting the N108 out without taking the injection pump out. No way. There are two bolts holding it in. We decided the injection pump was coming out.
And out it came! Actually, it was not too bad taking it out. We did have the bent wrench and that helped a lot. It was a bit strange the way the bolts went through the pulley and the bolt holders, but it went really well. The pump needs to be "wiggled" just right and it comes right out. Wiggling it just right can take some patience though. Then we looked at the N108, took the bolts out, and then tried to get it out.
It wouldn't budge.
We looked it over and then decided to use a screwdriver and a hammer to tap on the "ears" of the N108. We did that and also sprayed penetrant liberally. After a while we could see that we were bending the ears on the N108, so we quit. This was after about a half hour of tapping. After a break, we resumed and kept it up. After about an hour we could see that we moved the N108 about 0.010". Success! Then we upped the ante a bit by putting some vise grips on the metal ears and rocking it. We could only turn it a few degrees with the vise grip. The routine was turn, turn, tap, tap for about another hour. Then we used one of my secret weapons for loosening stuff without a torch - we poured boiling water on it. That helped a good bit and we could then turn it at will and the taps became more productive. We had it out about fifteen minutes later. It was pretty ugly after being beat upon for over two hours.
Much to our surprise the N108 screen was clean, as was the orifice it sat in. We were pretty puzzled as we felt sure that it would have been plugged. At this point we decided to test the N108 to see if it would do anything.
Naturally, Bentley didn't tell us what voltage drove the thing. We were able to measure some resistance across the terminals but so what? We wanted to know if it actually worked. So we played around thinking that if we drove it with voltage, "something" would happen. A click, or something. Thinking that the N108 might be driven by 5 volts or so we rigged up some batteries and hooked them up but no response. We then tried 12V and voila! We were able to get an audible click. We then placed a small hose over the "tube" part of the N108 and we pumped it up to 25 psi with an air pump. We monitored the pressure gauge for a couple of minutes and guess what? It held gas pressure! BTW we were "driving" the gas flow the opposite way from how the fuel flows through the thing. No biggy. If the valve holds gas pressure it will sure as heck hold fuel back (remember liquids have viscosity values of about a million times more than gases). We then energized the valve and the gas pressure was relieved. We repeated this a number of times. We decided that the N108 was OK, so we put it back. BTW fivestring had new O-rings for the N108 and the inner one - having the correct p/n on the package - was in fact the wrong size so we reused the old one.
We then checked the timing using the normal method: put the pump pin in place, crank at TDC, etc., etc. We put the timing belt back on, hooked everything up and went for a ride and guess what?
It ran the same friggin' way as when we started! And threw the same code! Of course, this made sense as we didn't really CHANGE anything. We did waste about 30 man-hours though....
So, at 5PM on a Sunday... we looked at the VAG-com timing and sure enough, requested timing was 1.5 degrees BTDC and actual was 6.5 degrees BTDC. N108 duty cycle was about 70% (I believe... I am typing all this from memory). So, we figured that maybe the timing was off more than the N108 could compensate for. So much for it being a "cold start" injector. Its a timing device thats needed all the time, evidently.
Since the timing was more advanced than requested we loosened the pump bolts and pulled the pump housing in the direction of rotation (clock-wise looking at the engine from the passeneger side to the driver's side). Said another way, this was like pulling the top of the pump toward the front of the car. We were able to put a socket wrench through the pump pulley just by taking the TB cover off which saved time.
We started it up and whamo! Smoke all over the place and a horrible knock. Timing was now at something like 1.5 BTDC requested and 18.5 BTDC actual. So, we repeated the process and pushed the thing back the other way - toward the back of the car and guess what.... it now ran like a dream!!!!!
Timing requested and actual matched. N108 duty cycle percentage was down to around 40%. We went for a ride and it ran strong and quiet with no CEL.
Moral of the story. Check the timing. Lessons: BTDC to VAG-com must mean "beyond" TDC and not "before" TDC. Strange. The other thing I noticed is that the injection pump housing setting procedure is discussed in the injection pump part of the A3 Bentley and not in the timing belt section where it would seem to rightly belong.
Here is my take on what is going on with the N108 problems. Its a timing issue and related to timing belt replacement. The timing belt replacement procedure requires that the injection pump pulley and the crankshaft be locked down. The belt is then placed on and tightened. The problem is that there is no way to put tension on the timing belt in between the crank pulley and the injection pump pulley - they are fixed! So what happens is that all of the initial belt tension is around only a portion of the belt: from the crank pulley clockwise around to the injection pump pulley. When the car is started and the belt tension equalized then the injection pump timing naturally becomes slightly retarded from where it was (the distance along the belt path from the crank pulley to the injection pump pulley increases as the belt gets pulled harder).
I think that the timing belt procedure should be changed to incorporate injection pump setting. One way to do it would be to loosen the injection pump and move it forward to a retarded position before the belt is tightened at every timing belt replacement. That way, it would give you plenty of room on the slots to move the injection pump to the advanced direction (based on N108 duty and/or timing results from VAG-com).
Long one... sorry folks. Any comments???