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gtroth's Avatar
 
Join Date: Oct 2003
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groan - fuel pump?

After 20 minutes or so of driving, I start to hear a groan that seems to come from right rear. I can only hear it from inside the car. I am guessing fuel pump, but po changed that in Jan 2003. I just replaced the original fuel filter in case that was gunked up, but it didn't help.

The groaning doesn't stop once it begins (unless its sits overnight, say). Should the fuel pump be running all the time anyway after 20 minutes of running? I thought it was supposed to run intermittently to keep fuel pressure up.

Any ideas?

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Old 11-21-2003, 04:08 PM
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Fuel pump runs all the time.

The fuel recirculates picking up heat from the engine.

Replace the fuel filter first before you think pump.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 11-21-2003, 04:14 PM
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ok, so I changed out the fuel filter a few weeks back, but the groaning was unaffected. Lately, it seems loader. Is this definitely the fuel pump? Is it going to fail and leave me stranded? Remember, the pump is only one year old.
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Old 12-30-2003, 04:25 PM
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Yes I didn't read your first message very well.

Hydraulics will make noise when there is a restriction. Common to the under the body fuel lines is to have one piched closed by road fod. Look along the lengths of the two lines for bends and dings. If you are not loosing performance then check the return line more than the feed.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 12-30-2003, 05:11 PM
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Yeah, I didn't read it very well either (forgot I mentioned the filter change...). I'll check those lines, maybe banged one with a jackstand, but I don't think so.

The noise does sound as though it could be fluidic (maybe even cavitation? what kind of pump is a fuel pump anyway?). But I could also convince myself that it's mechanical noise.

I'm also wondering about what you said about the fuel picking up heat from the engine. Could somehow explain why the noise takes a while to start.

Thanks again , Hugh.
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Old 12-30-2003, 06:49 PM
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Hot fuel will affect a fuel pump. Since the fuel recirc's it's possible to heat up a low tank. You need to park it when it's making the noise and check behind the passenger wheel for it's actual location.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 12-30-2003, 06:56 PM
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I really can only here it when inside the car (too noisy outside with the car running). I'll try a little harder before I start inspecting the lines.
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Old 12-30-2003, 07:09 PM
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The fuel pump on my 81 924 is loud. From what I can tell it was designed that way. Since I have never owned a 944 I cant coment on your groan.
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Old 12-30-2003, 07:11 PM
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If the noise is coming from the back inside then it could be the gas tank venting.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 12-30-2003, 07:12 PM
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...some thread maintenence -

Solution - Fuel Pressure Regulator. Fuel pressure was pegged >100psi, once replaced, reads nominal and groaning in the fuel pump is gone. Drove it 6 hours today (instead of my usual 1 hour), so I'm reasonably sure.
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Old 02-15-2005, 02:43 PM
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Thanks for the feed back.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 02-15-2005, 02:50 PM
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You drove for 6 hours today? Holy crap, did you just take a lap around CT??

Glad you got your problem resolved
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Old 02-15-2005, 03:52 PM
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Boston and back.
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Old 02-15-2005, 05:32 PM
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Oh, and MPG went from 22 to 25. And warm start doesn't require 5 cranks or so like it used to (the fuel pressure leakdown went from dropping from >100psi to below spec in <1 minute to essentially holding pressure forever).

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Old 02-16-2005, 04:05 PM
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