TDI timing problems, electrical...

[houseofdiesel]

1996 Passat 1z TDI, 430,000kms,
Car came in with injection pump in trunk (traded in through dealer networks...)
I removed the cylinder head, had no idea what might have happened to the car since it was traded through a couple dealers. One owner car that was recently maintained. The intake was completely plugged (99%), water would barely trickle through. Head had two valves leaking. Rebuilt head, installed used injection pump from another forum member, new timing belt, seals etc. Had a real hard time starting car, fuel was present. Tried brake cleaner in intake, car started. It runs fantastic! Lots of power through the entire rpm range, no check engine light. (scanned). Drove a couple hours and filled with good fresh fuel.
When I check pump timing however, column 2 in the basic settings (timing spec) jumps from 45 to 255 instantly and then idles rough. Car will not start cold, starts fine hot. Everytime you go into the timing setting it goes from 45 to 255 instantly and starts smoking/running rough at idle. You have to use a strting aid to get it going cold. Once running it is fine. Glow plugs are find and outside temp is not really a factor (won't start when parked indoors either at 15C). Any thoughts? It must be electrical but what-computer?
Greg

[QuickTD]

I'm not an expert on TDI's, but doesn't putting a TDI into "basic settings" remove all the computer control of the timing and allow you to observe and adjust the mechanical base timing? In this case, if your mechanical timing is well out of whack (retarded) the engine will run rough and stumble when placed into "basic settings" mode because the correction will be turned off.

 If the mechanical timing is retarded the engine will be very difficult to start. ECM control of the timing advance cannot occur until the injection pump has sufficient housing pressure to drive the advance piston, so if the mechanical timing is out of whack the ECM cannot correct it at cranking speed.

[houseofdiesel]

Good point, hadn't thought of it that way but we did adjust the timing on the pump (by rotating the pump body) and it didn't change the number once the 1551 was plugged in-it changed the number it would flash before going to 255...(started out at 4, now 45 but always becomes 255 once the vag com is inserted)
Greg

[QuickTD]

255 is the highest possible value of the 8-bit data word, indicating that the timing value is at the maximium (or minimum depending on how the value is interpreted). Is it possible the timing is out too far (1 whole tooth or more) to get the value within the measurable range by just turning the pump? Maybe you should recheck the placement of the belt and make sure the timing pin will go in when the engine is near TDC.

[houseofdiesel]

Well the timing belt timing was triple checked, everything there is fine, the cam locks perfectly and the pump pin fits snug and TDC on crank is fine. The timing is fine once the car is running, however when you plug in the 1552 scan tool it sends the timing to max value of 255 and idle gets rough/smokey. Adjusting the pump timing by rotating the pump body does nothing to change this, everytime the computer is hooked up the idle changes and the value goes to maximum. The number is column 2 comes on at 45 but then flashes immediately to 255, rotating the pump will change the initial number but it always overides to 255.
The car will not start-meaning when it turning over it sends the pump to this max value, once started it drives/runs with all the power it should have and no smoke. What is wierd is the absence of a check engine light, it should sense the timing change and throw a code...
I think the ecu is problematic or a sensor is giving a wierd value, I would change the injection pump back to the original one (which VW dealer diagnosed as bad) but I don't have the time/too cold outside/too busy in the bays...I talked with the dealer in question and they said the car had bad fuel/contamination and left it right there-car was just diagnosed, never taken apart, traded in on a new one and wholesaled off. Car arrived at work with injection pump in trunk-who did this I will never know! That is why I pulled the cylinder head off to see if valves where damaged etc.
It is not a simple timing issue with belt being off one tooth or the pump not timed properly, this is an ecu problem or pump or sensory etc.
Greg