Help, AHU injection timing issue

Houpty GT

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Aug 31, 2008
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Corrado TDI, 2000 Golf, 1996 B4 Variant
That is going to retard the injection timing. Moving the gear clockwise will move the pump advanced in the timing belt cycle. This will have the same effect as moving the injection pump housing to the rear of the car. It's easy to get mixed up because they are opposite of one another.
 

ToddA1

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Aug 3, 2011
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'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Yup, I can confirm CW. I‘ve needed to do this on several cars after a belt swap.

-Todd
 

turbodieseldyke

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Free Mustache Rides
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98 jetta
You're right. You want to "rotate the pump" toward the engine. So turning the pulley CW while leaving the pump stationary, would have the desired effect.

He can try it either way to see which works best, without breaking anything.
 

Poiuqf

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Mar 15, 2022
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NC/VA
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1998 mk3 vw jetta tdi
So, rotating the pump, one tooth, either way, the pin does not go into the timing hole anymore. Does this matter?
 

Vince Waldon

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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Honestly, your best bet, now that you know for sure where TDC is, is to do the proper alignment proceedure with the belt untensioned, cam locked at TDC (#1 lobes up), cam sprocket loose, IP locked, crank at TDC, then tension the belt.

Should find more details in the A3 Timing Belt proceedure here:


This way you will know both cam and IP timing are reset and there should be no reason for any one-tooth workarounds. :)
 
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turbodieseldyke

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98 jetta
So, rotating the pump, one tooth, either way, the pin does not go into the timing hole anymore. Does this matter?
No. The pin is supposed to guide you where to set the pump. You need it to run, regardless where the pin goes.

The cam and crank, however, do need to stay at their correct marks.
 

Mongler98

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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
So these pump sprokets are not able to move. 3 bolts.
If everything is in time properly then it should be good.
when i do the TB job i always find that you have to fiddle with the IP sprocket to make it lign up. its entirely possible that you are actually a tooth off on the IP.
i would NOT suggest you intentionally set it off to compensate.
 

Poiuqf

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Mar 15, 2022
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1998 mk3 vw jetta tdi
So these pump sprokets are not able to move. 3 bolts.
If everything is in time properly then it should be good.
when i do the TB job i always find that you have to fiddle with the IP sprocket to make it lign up. its entirely possible that you are actually a tooth off on the IP.
i would NOT suggest you intentionally set it off to compensate.
i just re-did the timing belt, all timing marks still lining up, perfectly. Yet same problem persists, while trying to dial in injection timing, all I get is a vertical yellow line, or 255 being the value, no matter where I rotate the pump. The car runs pretty decently with injection timing all the way advanced and any little bit of trying to retard the injection timing results in it idling extremely rough.
Im going to attempt to rotate the i.p one tooth clockwise, just to see if it does anything, other than that I think it’ll be time to pull the pump.
 

Mongler98

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Mar 23, 2011
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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
i just re-did the timing belt, all timing marks still lining up, perfectly. Yet same problem persists, while trying to dial in injection timing, all I get is a vertical yellow line, or 255 being the value, no matter where I rotate the pump. The car runs pretty decently with injection timing all the way advanced and any little bit of trying to retard the injection timing results in it idling extremely rough.
Im going to attempt to rotate the i.p one tooth clockwise, just to see if it does anything, other than that I think it’ll be time to pull the pump.
yea... worth a shot... but i suspect the pump is worn down. that or the crank sprocket is worn down as well. does it fluctuate at all or is it rock steady at that value?
you wont hurt anything at all by skipping a tooth on the IP so... fingers crossed.
just out of curiosity... could you check the wireing harness on the IP (both cables) and plugs and the harness for the engine for any rubbing or broken wires? this would not be the first or the last time that a corroded plug or broken or severely damaged wire caused crazy results like this.
 

Vince Waldon

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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Hmmmm, yeah that's a bit strange.

Just double-checking that you've got the pump more-or-less centered midway in the slotted holes, pin lock in the sprocket, when you installed the timing belt?

Mid-way in the slotted holes so as to maximize the amount of adjustment you can make.
 

Poiuqf

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Mar 15, 2022
Location
NC/VA
TDI
1998 mk3 vw jetta tdi
I’ve already went over all of the wiring and found nothing out of the ordinary. But success? Just drove the car around the neighborhood, it didnt get all the way up to temperature but, just hooked it up to vcds and the injection timing was around 163 and the cold start valve value was 3.7%. I’ll try fine tuning the injection timing tomorrow, ran out of daylight. But seeing a value other than 255 makes me happy right now.. haha
 

Mongler98

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Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
I’ve already went over all of the wiring and found nothing out of the ordinary. But success? Just drove the car around the neighborhood, it didnt get all the way up to temperature but, just hooked it up to vcds and the injection timing was around 163 and the cold start valve value was 3.7%. I’ll try fine tuning the injection timing tomorrow, ran out of daylight. But seeing a value other than 255 makes me happy right now.. haha
good enough... those timing values must be at operating temp.
Since you have a rough idle ..... what is the IQ set at?
 

Poiuqf

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Joined
Mar 15, 2022
Location
NC/VA
TDI
1998 mk3 vw jetta tdi
Only idled rough when adjusting the injection timing, retarding it, prior to moving with injection pump gear one tooth. Runs pretty decent as of now, barely any smoke. If I’m able to adjust the injection timing by rotating the pump, and It actually changes the value, then it would seem that rotating the pump gear one tooth did the trick.. IQ was at 4.something
 

Poiuqf

Member
Joined
Mar 15, 2022
Location
NC/VA
TDI
1998 mk3 vw jetta tdi
I was finally able to dial in the injection timing via VCDS. I don’t understand it but I’m glad rotating the injection pump one tooth clockwise miraculously did the trick. I appreciate all the help and information from everybody.
 

Mongler98

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Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
awesome.
im not sure why it needed to be done but hey... its a 25 year old car with a LOT of miles so grains of salt right?
the AHU IMO is a much better bullet proof platform vs the ALH.
as long as you do not over heat it or kill it with boost.... it should live forever....
my bet is on a worn out pump but as long as its running..... drive more worry less. you sound very competent to keeping her healthy so thats good!
 

Poiuqf

Member
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Mar 15, 2022
Location
NC/VA
TDI
1998 mk3 vw jetta tdi
Yeah exactly, I figured I’ll just keep my eye out for spare injection pumps if it decides to crap out on me. But in the mean time, I’ll be curious to see the mpg difference, with the considerable less amount of smoke. Love these cars. (y)
 
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