[Vwdiesel] *help! smoking & bucking*

[James Hansen]

Rolf Rolf Rolf....
You have some kind of mechanical failure field machine you been working on?

TURN IT OFF NOW, it's working.

> - engine light is NOT on

Does it come on when you turn the key to run, with engine not running?  IE:
is the bulb burned out?

> 
> thoughts:
> 
> - CPU clearly not driving the fuel pump properly
> 
> Q's:
> 
> - is it possible driving while running the battery down damaged the
> fuel pump CPU??

No, faiure mode is generally like a switch. Working, or not working.

> - or even the fuel pump itself?

unlikely

> 
> - shop charged up the battery before doing the alt
> if they had reverse-connected the charger, could it have fried the CPU?

Not with the key off.

> 
> - would the car run at all if the CPU were fried?

Unlikely

> 
> - might pump timing need to be re-set? isn't that all CPU-driven?

May have lost the adaptation.
Timing is still mechanical.  It is tweaked by the ecu, but has to be real
ballpark to work well.

> 
> - what else could explain this behavior?

MAF mass airflow sensor.
Unplug it, and try to drive.

That's about the most delicate thing there.  It's a resistance heating
element- dropping voltage messes with it, MAY have killed it.  Don't suppose
you have your  copy of VCDS along?
I would be tempted to reboot.  Disconnect battery ground from battery for a
couple minutes, then reconnect.  Run vcds, scan for engine faults, copy,
save, and clear them.  Then run the engine, and see what comes back.
Good luck bud.
-james