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Registered
Join Date: Jun 2009
Location: Santa Fe, NM
Posts: 1,035
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Fuel Pump Sound
As I was working on my lights project, I had the key on and off a few times to test, etc. I usually pull the fuel pump relay in advance knowing that I don't want to flood the intake.
When I got it all done, I replaced the fuel pump relay, and turned the key two clicks to check if I get that fuel pump sound. No sound! So I turned the key farther and it started right up. I switched relays and it still started, but no sound. Then I pulled the fuel pump relay and no start, so I know the relay is good, and the fuel pump must be working. Why no sound? Residual pressure already in there? Should I go drive it? Is my fuel pump about to fail? I replaced it new a few years ago. Or am I all good to go?
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Scot 78 911SC coupe, sold,, 2019 Macan S "my friends all drive Porsches, I must make amends.." |
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01-24-2016, 03:09 AM
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Almost Banned Once
Join Date: Feb 2009
Location: Adelaide South Australia
Posts: 38,447
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The fuel pump should only run when the engine is running or starting so what you're describing is normal.
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- Peter |
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01-24-2016, 03:37 AM
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Registered
Join Date: Oct 2005
Location: Capistrano Beach, Ca.
Posts: 7,235
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Quote:
All CIS cars from '76 on, use the relay which prevents the pump from running unless the engine is in "start" mode or is otherwise running. Knowing this, you do not need to remove the relay when working on things that require the ignition to be switched on an off as the pump should not be running. Removing the relay is good insurance, and if you do notice the pump running with the ignition on, that is a sign something is wrong.
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L.J. Recovering Porsche-holic Gave up trying to stay clean Stabilized on a Pelican I.V. drip |
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01-24-2016, 07:22 AM
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The air cleaner housing has a sensor plate for the fuel injection when you start the engine it draws in air raising the plate. When the plate lifts it' breaks a connection that's holding the relay open then the relay closes the circuit to the fuel pump turning it on.
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01-24-2016, 07:58 AM
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