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More Prepump Questions[200/84] posted by Steve L on
Tuesday, 13 October 1998, at 12:19 a.m.
How long should the in tank pre-pump last? Should you change it out BEFORE it breaks and kills the main pump? Or just wait until it dies?
I got a used 240 GL with 144K and the in tank filter sock is torn to shreads. Who knows how long it has been that way, letting all kinds of krud into the pre-pump. The pre-pump seems weak, but it still runs. Should I change it now, along with the filter? And if in future I change the filter sock regularly, say every 45,000 miles or whenever I change the main filter, will the pre-pump then live forever?
The car runs great now, and I want to keep it that way. Thanks in advance for your suggestions.
Steve
Re: More Prepump Questions[200/84] posted by Bob Mohr on
Tuesday, 13 October 1998, at 10:47 a.m.
My suggestions:
Pull the fuse for the pre-pump and connect an ammeter across the fuse holder. Start the engine and measure the current that the pump pulls. Check the Bosch spec in your Bently manual, but if memory serves me right it should pull around 1.1 amps. Anything higher than say 1.8 amps probably points to a failing pre-pump.
With the car idling, locate the main fuel pump - driver's side, beneath the car. Is the pump case hot? If it's uncomfortable to keep your hand on the pump for any length of time, the main pump is overworking, trying to pull suction from the tank through a sluggish pre-pump.
Hope this helps.
Bob Mohr