Sunday, May 28, 2006

The evil accelerator pump


VW Accelerator pump
Originally uploaded by Phil_Parker.
Bently says “7. Poor transition from idle to operating speed”

My symptoms, engine ticks over OK but if you press the accelerator it goes, “bobble bobble pluuuu” and either revs or stalls.

Sounds like the same thing then !

Out comes the carb, onto the bench where it is stripped down again. Carb cleaner is sprayed through all the passages as I try to work out where they run. The books tells me to investigate the accelerator pump so I do. A bent tube points down into the throat of the carb and after spraying and poking wires this appeared to be the problem. More spraying and poking with it out of the main body and I finally get it clear. A fair amount of crud was pulled out from behind the diaphragm too which can’t be a bad job done. I still don’t really understand what this bit does – best guess is it gives a shot of petrol when you accelerate, presumably to avoid a flat spot during the engine speeding up.

Reassembly is the reverse etc. etc. Everything was better but still not great. However it was good ebough to warrant a gentle test run where things improved. Not more rough transition from idle to acceleration. Presumably the crud left in the pipe (there was some as the van still hesitated on hard acceleration) had been blasted through the system.

Tomorrow we are going for a proper test run with hills and everything !

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