[Vwdiesel] sparks out the tailpipe

[William Longyard]

If you saw "tongues" of flames, I would attribute that to the carburetor 
sucking too much gas during a period of high vacuum.  However, you said you 
had "sparks".  Shooting "sparks" are usually bits of carbon in the steel 
burning, and that makes me think you have cylinder/ring disintegration 
issues.  Of course it could also be you have chucks of carbon burning off 
your cylinder head, or even a valve disintegrating.  Whatever, I think it's 
time to pull the head and have a look.

Bill Longyard