EA81 engine lagging after sustained acceleration

[patrickfrancis]

Hi All

I've been struggling with a fuel issue in my EA81 engine (in a converted VW btw). 

I have finally gotten to the bottom of it and though I would share my experience for others experiencing similar problems...

 

Problem: Engine failing after sustained periods of acceleration - bucking, lagging for 5-10 seconds, then starting again.

Work undertaken: Fuel pump replaced, fuel filter replaced, carbi rebuilt

Solution: Problem caused by fuel pressure/vacuum build up. It is understood that the engine originally had a fuel vacuum relief (either on filter or fuel cap), which had been removed in the process of replacing parts i.e. capping line to charcoal canister, fuel filter etc. The solution was to allow for venting via the fuel cap.