Noisy Fuel Pump -

[zcat3]

Hey Guys - the fuel pump in my new 69S is quite noisy. When I first turn the key it is very loud as it pressurizes the fuel system and then continues to make periodic noises loud enugh to be heard while driving. The car runs fine with no evident fuel system issues. Is this noisiness normal?

[B D]

What type of pump orginal or aftermarket? The rotary pumps (usually faccet) common on VW's are quiet noisy, the good you know it works the bad it's noisy. PMO sells a nice pump made by Pierburg that is self regulated at 3.5 lbs of pressure which is the ideal pressure for Webbers and PMO carbs. The cost of the new pump and piece of mind $80.

[pwd72s]

BD, if I'm not mistaken, the '69 S was the first year of MFI...so I don't think a fuel pump pressurized for carbs would work. The correct pump for MFI is Porsche # 901.608.105.00 Bosch #058097 0001. (14.2 psi) These are old numbers, probably need updating. (info gleaned from a Grady Clay post on Pelican) FWIW, the Porsche pump for carbs was originally 4.3 PSI...Porsche #
911.608.107.00, Bosch #058096 0009. Hope this helps...

[Chuck Miller]

Bill,
You may not be crazy!!!! ...

Sometimes these fuel pumps ARE noisy as hell ... Mine being one
Noisy enough to be heard over a quiet stock-muffled old 911...

A very high pitched hummmmmm .... Mine has been sounding that way go'n on 16 years... The more blown-out my muffler gets, and the more hard of hearing I become... the less I notice it

... and so it goes

Cheers,

[pwd72s]

Huh? What fuel pump noise?

[zcat3]

Just like the funky rear spring plate bushings that make the car sound like it's coming apart, the pump could be vibrating. Check it out for tightness of the fasteners etc.. And, don't feel like the Lone Ranger.

Tom

Yep - I have that rear spring plate clunk as well. I thought it might be the sway bar, but the more I hear it the more it sounds like it is from the rear torsion bar tube - almost like the driver's side torsion bar slides back and forth.

As for the fuel pump, I am not sure what version it is. I am told the car has carbs (the stacks do say Webber on them) so perhaps the fuel pump was changed at that point. I will take a look at it tomorrow.

[Grady Clay]

Bill,

There are a couple of other possibilities not mentioned here:

When the MFI was replaced with carburetors, the fuel pump needed to be changed to a lower pressure pump. If they didn’t use the 911T Bosch pump, another pump might not fit in the space or in the rubber mounted cradle. This allows the pump to contact the chassis or cross member and transmit the noise you hear.

Another possibility is the pump is cavitating some of the time. This situation is particularly noisy with rotary pumps. Have you checked and measured the fuel flow back to the fuel tank when bypassing the carburetors with a long hose from the engine to the fuel filler? It is possible the filter screen in the fuel tank fitting is restricting the flow.

Since your 911 was originally a MFI fuel recirculation system, you can install a “bypass” type pressure regulator at the engine and use the existing return fuel line. This is good for preventing vapor lock and getting cool fuel to the carburetors.

Paul, thanks for posting the numbers. You are correct, '69 was the first year for production MFI.

Best,
Grady

[Chuck Miller]

Grady,

Really glad you're contributing to this board bud ...

Allot of us hunt & peck ... You seem to keep the bullseyes in your pocket...

Thanks again,

Cheers,

[zcat3]

Thanks Grady - I did not get a chance to check the pump today as I spent most of the time installing new seat belts. I should have some time tomorrow to poke around a bit and at least get a part number off the pump.

[zcat3]

Well I finally checked out the fuel pump. It is actually mounted inside the engine bay right by the fuel filter. It did have a loose mount, so I tightened that down to see if that helps. That may have accounted for the clunk I heard while driving. The pump itself is pretty noisy though. It is an Airtex pump - something like model 12V-E12AX. Anyone know where I can get a replacement or if this can be refurbished?