SJ Audi 100 Won't Start (Vacuum Leak?)

Huw Powell audi at
Mon Feb 2 22:37:42 EST 2004

> Previously I'd tested the potentiometer resistance with the bonnet open.
> I'd found that The resistance between the bottom and the middle contact is
> about 2 kOhms at rest and rises to a max of about 13kOhms near full open
> falling slightly to 11kOhms at full open.  Today I decided to measure this
> resistance during an attempted start just to ensure that the plunger is
> actually moving.  The resistance moved from about 2 kOhms up to about 4 or 5
> kOhms. when it appeared that the engine was about to start and then as it
> sputtered the resistance fell back to 2kOhms.

Something about this has been bothering me since I read it... mostly 
because the pot. acts as a voltage divider on a 5v/G feed from the ECU.

Of course, measuring the varying resistance should be a fine way to see 
if it is clean and tracking properly, with the power off.

But while cranking/running etc., how can you measure a resistance that 
has voltage across it?

Huw Powell

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