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Author: Subject: Noisy LP fuel pump
CTLeeds

posted on 25/10/19 at 04:42 PM Reply With Quote
Noisy LP fuel pump

Hi all, I've just installed a Facet low pressure fuel pump and swirl pot in my car to feed the HP EFI pump to cure fuel starvation on fast right handers. I can't believe how noisy this LP pump is! It's banging away like a jack-hammer. Is this normal? I can't believe anyone would put up with this amount of noise constantly. I saw on a forum somewhere that an R1 motorbike pump would be good for this and really quiet.

Any thoughts appreciated.

Chris

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gremlin1234

posted on 25/10/19 at 05:16 PM Reply With Quote
have you mounted it rigidly to the body/chassis
or used a softer mounting kit?
https://www.fuelpumpsonline.co.uk/facet-fuel-pump-mounting-kit-fpa905-4-p.asp

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Andrzejsr

posted on 25/10/19 at 05:45 PM Reply With Quote
I have Facet low pressure fuel pump too, and it is noisy most of the time. I have noticed that it gets quieter when tank is full , (or with lot of ) fuel. I am in process of relocating the pump so it sits much lower than tank bottom , have read that when pump is lotated to high , then it is noisy. I looks like the case considering quieting with full fuel tank.





https://youtu.be/1OXvUrHfAVg?t=3

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CTLeeds

posted on 25/10/19 at 07:38 PM Reply With Quote
quote:
Originally posted by gremlin1234
have you mounted it rigidly to the body/chassis
or used a softer mounting kit?
https://www.fuelpumpsonline.co.uk/facet-fuel-pump-mounting-kit-fpa905-4-p.asp


It's currently floating and is noisy as anything. I also have a full tank of fuel with the pump at the level of the bottom of the tank. I'm not convinced it's priming properly but as it's a self priming pump how could I check?

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Jed

posted on 26/10/19 at 10:58 AM Reply With Quote
If you put a restriction in the return pipe from the swirlpot to the tank it may quieten it down. Some have used 0.8mm MIG welder tips in the return pipe but a piece of metal (I used brass) with a small hole will do the job. The return really only needs to allow air back to the tank in normal circumstances. Just make sure that it is of a large enough diameter not to get pushed into the tank.
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40inches

posted on 26/10/19 at 11:21 AM Reply With Quote
quote:
Originally posted by Jed
If you put a restriction in the return pipe from the swirlpot to the tank it may quieten it down. Some have used 0.8mm MIG welder tips in the return pipe but a piece of metal (I used brass) with a small hole will do the job. The return really only needs to allow air back to the tank in normal circumstances. Just make sure that it is of a large enough diameter not to get pushed into the tank.


This makes a huge difference to the noise from the LP pump. I used a 0.8mm mig welding tip.
If you temporarily pinch off the return hose with a pair of pliers, you should hear the differance.
As Jed said the return is an air bleed, not a fuel return. I used brake pipe for mine.

[Edited on 26-10-19 by 40inches]

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CTLeeds

posted on 26/10/19 at 08:29 PM Reply With Quote
quote:
Originally posted by 40inches
quote:
Originally posted by Jed
If you put a restriction in the return pipe from the swirlpot to the tank it may quieten it down. Some have used 0.8mm MIG welder tips in the return pipe but a piece of metal (I used brass) with a small hole will do the job. The return really only needs to allow air back to the tank in normal circumstances. Just make sure that it is of a large enough diameter not to get pushed into the tank.


This makes a huge difference to the noise from the LP pump. I used a 0.8mm mig welding tip.
If you temporarily pinch off the return hose with a pair of pliers, you should hear the differance.
As Jed said the return is an air bleed, not a fuel return. I used brake pipe for mine.

[Edited on 26-10-19 by 40inches]


I did try crimping the outlet pipe of the pump and it made a bit of difference. I guess they like having a resistance to pump against rather than being free flow. I'm interested in the theory that the return is air only, is this a carb thing? Mines EFI and there is a flow of fuel in the return line.

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rusty nuts

posted on 27/10/19 at 06:59 AM Reply With Quote
I wouldn’t worry about it, when your driving you won’t hear it above all the other noises
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rusty nuts

posted on 27/10/19 at 06:59 AM Reply With Quote
I wouldn’t worry about it, when your driving you won’t hear it above all the other noises
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TimC

posted on 28/10/19 at 10:30 PM Reply With Quote
As a reference, you can hear mine (mounted on bushes) after I flick the third switch here:







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Mr Whippy

posted on 30/10/19 at 12:32 PM Reply With Quote
As above the reason it's thumping away is it can't build up pressure, are you sure it even needs a return? the old style ones for carbs I used would only do a pump stroke when the pressure dropped to a certain level, so initially when you turned on the ignition it would thump away and then slow or stop once the carb was full and then only stroke again when required which may only be a few times a minute. If it kept going it meant you either had fuel or it was pumping fuel all over the floor cos your fuel lines fallen off...
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CTLeeds

posted on 30/10/19 at 12:58 PM Reply With Quote
quote:
Originally posted by TimC
As a reference, you can hear mine (mounted on bushes) after I flick the third switch here:



Thanks for the video. Mine sounds exactly like that but my engine's a fair bit quieter. Maybe the solution is a louder exhaust!

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