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Matt, Engineer
Category: VW
Satisfied Customers: 21111
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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1979 VW Super Beetle: fuel pump runs..the ignition key is turn on

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1979 VW Super Beetle. Just purchased. The fuel pump runs all the time as soon as the ignition key is turn on. Is this normal?
It looks like previous owner ran a new wire to the fuel pump which is a Bosch type mounted under the gas tank. Car starts, runs and goes, but it seems a bit loud and annoying.
Basic steps to trouble shoot?

Most likely the original wiring developed a fault and rather than fix it the previous owner just ran a switched live wire to the pump.

The pump should run for a few seconds when you 1st turn on the ignition and it then uses a feed from the starter solenoid to keep it switched so it won't run unless the engine is running/
However to sense this there's a relay with a timed circuit in it which can be unreliable so 1st locate the pump relay and check its contacts are bright and clean and consider replacing it .

Also the pump should be mounted with some rubber anti-vibration mounts so it shouldn't be that loud unless its an after market pump
Customer: replied 6 years ago.


I would like to know about how long the pump should run after a running engine is stopped by turng the key to the non running position but ignition on? Also, is pressure regulator in the pump? Are you familiar with the air flow waffle valve?



the pump should stop running within a second or two of the engine stopping, I think is the Bosch K jetronic on this car - the mechanical fuel injection so the pressure regulator is built into the fuel distribution manifold / device

and air flow waffle valve? can't say I've come across that term.

this diagram should help with the diagnostic

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