Lotus Elan

replacement electric fuel pump

PostPost by: Andy Hamblin » Mon Jul 27, 2020 1:21 pm

Hi all, I have replaced my mechanical fuel pump with and electric one and mounted it on the pedal box. It was one I had hanging around as a spare for my previous car which had a temperamental SU pump. Its a cheap and cheerful Chinese thing which functions fine but it is very noisy and I can't live with it. It makes a loud ticking/clacking noise which would probably be ok if it were rear mounted, but not where it is in the engine bay.

Does anyone have any suggestions or recommendations for a reasonably quiet and fairly compact pump? It would also need to be fairly low pressure, the one I have is 3-5 psi which seems to be about right for the Strombergs.

An SU size/style pump would be more difficult to fit in the space I've got. There are plenty of pumps which would appear to do the job, but until its installed I wouldn't know if its quieter or not - grateful for any advice. Thanks.
Sept 1970 Plus 2S, KOO38J Glacier Blue, 50/2432 (was Carnival Red)
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PostPost by: sprintsoft » Mon Jul 27, 2020 1:57 pm

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PostPost by: lotusfan » Mon Jul 27, 2020 2:06 pm

Hi Andy

Have a look at Hardi pumps https://www.hardi-automotive.com/en/pro ... uel-pumps/

I replaced the SU pump in an MGA with one and it really is very quiet. If you could physically fit it in your +2 you won't be disappointed with the noise. They are viewed as one of the more reliable pumps around.
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PostPost by: mbell » Mon Jul 27, 2020 5:27 pm

I am thinking about a 60304 FACET POSI-FLO for my car when I get around to reworking the fuel system.

I have weber carbs so prefer lower (1-2PSI) pressure pump. Currently have one like:
https://www.amazon.com/gp/product/B00496RE82

Mounted near pedal box area. I measured it at 3.5PSI. This seem to be the pump offered by Rdent. It is very audible with engine off but I don't notice it with engine running.
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PostPost by: Andy Hamblin » Mon Jul 27, 2020 8:10 pm

many thanks gents. All good suggestions that I will check out.
Cheers,
Andy
Sept 1970 Plus 2S, KOO38J Glacier Blue, 50/2432 (was Carnival Red)
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PostPost by: elangtv2000 » Tue Jul 28, 2020 7:43 pm

I use a Redline low pressure fuel pump. Very compact, pretty quiet, more so if on a soft mount. Does better as a pusher than puller however, so mine is mounted in the trunk.
http://www.redlineweber.com/SEMA2002/ht ... _pumps.htm
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PostPost by: StressCraxx » Wed Jul 29, 2020 3:38 am

elangtv2000 wrote:I use a Redline low pressure fuel pump. Very compact, pretty quiet, more so if on a soft mount. Does better as a pusher than puller however, so mine is mounted in the trunk.
http://www.redlineweber.com/SEMA2002/ht ... _pumps.htm


Electric pumps don't like taking suction lift prime very well, so mounting them back at the tank is best practice.
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PostPost by: Andy Hamblin » Wed Jul 29, 2020 9:43 am

StressCraxx wrote:
elangtv2000 wrote:I use a Redline low pressure fuel pump. Very compact, pretty quiet, more so if on a soft mount. Does better as a pusher than puller however, so mine is mounted in the trunk.
http://www.redlineweber.com/SEMA2002/ht ... _pumps.htm


Electric pumps don't like taking suction lift prime very well, so mounting them back at the tank is best practice.


based on the advice of others on the forum, I have ordered the Huco:

https://www.dellorto.co.uk/shop/car-acc ... mp-133010/

It says: "This pump is a suction type and designed to be fitted in the engine bay of the vehicle." so I'm hoping it will be ok.

Thanks for all the advice and recommendations.
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PostPost by: Andy8421 » Wed Jul 29, 2020 6:29 pm

StressCraxx wrote:
elangtv2000 wrote:I use a Redline low pressure fuel pump. Very compact, pretty quiet, more so if on a soft mount. Does better as a pusher than puller however, so mine is mounted in the trunk.
http://www.redlineweber.com/SEMA2002/ht ... _pumps.htm


Electric pumps don't like taking suction lift prime very well, so mounting them back at the tank is best practice.

It was common practice to mount an SU pump in the engine compartment on T series MGs. Apparently the introduction of higher octane fuel caused vapour locks which were avoided by rear mounting the pump. Interesting to note that the standard pump on the Elan is engine mounted and therefore a 'sucker' rather than a 'blower', and its not clear to me why that would behave any differently to an electric pump.
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PostPost by: elangtv2000 » Wed Jul 29, 2020 7:32 pm

Mechanical pumps use a diaphragm which pulls a suction without relying on the liquid itself to seal to rotors, vanes, or pistons.

Think of a vacuum bulb gas siphon vs. a pump. If you use the vacuum bulb and hose, you will suck the fuel up above the static level of the tank, until it flows by siphon effect. Try to hook up a rotary or piston pump to a hose and drop the hose in the tank and the pump will spin but not be able to create a suction.
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PostPost by: MrBonus » Wed Jul 29, 2020 7:48 pm

I have a Redline pump mounted in the trunk. It's pretty loud when first primed but you don't hear it once the engine is running unless you really listen for it.
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PostPost by: Andy8421 » Thu Jul 30, 2020 5:10 am

elangtv2000 wrote:Mechanical pumps use a diaphragm which pulls a suction without relying on the liquid itself to seal to rotors, vanes, or pistons.

Think of a vacuum bulb gas siphon vs. a pump. If you use the vacuum bulb and hose, you will suck the fuel up above the static level of the tank, until it flows by siphon effect. Try to hook up a rotary or piston pump to a hose and drop the hose in the tank and the pump will spin but not be able to create a suction.


Your point is well taken, but SU electric pumps use a diaphragm - so in principle would be exactly the same as the engine mounted pump.

https://mgaguru.com/mgtech/fuel/fuel.htm

Your response would also suggest that other electric fuel pumps need to be mounted below the level of the fuel in the tank as they don't self prime. The two Facet pumps I have in the Elan I race are both mounted above the level of the tanks, and manage to operate just fine.
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PostPost by: elangtv2000 » Thu Jul 30, 2020 1:48 pm

Good point. I wasn't trying to be exhaustive describing all pump technologies. As the SU is a diaphragm pump, it does fit my statement about being able to pull a suction, and why some electric diaphragm pumps can be mounted in the engine bay, while some rotary or piston pumps need to be below the fuel level.

Regarding rotary or piston pumps, I wasn't trying to imply absolute characteristics, and it should be noted that the various types of electric pumps have different dry lift capabilities. The Facet round pump is stated to have more than double the dry lift capacity of the cube pump, but also may require a regulator as a result of the additional pressure.
https://www.merlinmotorsport.co.uk/know ... ettors-282

The OP has apparently found a pump that has sufficient dry lift capacity to be mounted up front, which seems to be the result of design details.

Regarding placement, my own preference is for the boot, because I don't want to jam more stuff and wiring into the engine bay, and to perhaps prolong the life of the pump by reducing temperatures. Regarding noise of the Redline Weber pump, I found using the included strap mount allows the pump to transmit more noise, but using a soft rubber standoff really reduces the noise. With the motor running, it's not audible either way in my S3.
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PostPost by: baileyman » Thu Jul 30, 2020 5:07 pm

My Huco pusher in the trunk could not dry lift the fuel out the top of the tank. I hope if I ever run out of fuel it will remain "wet" enough to lift on refueling. John
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PostPost by: elangtv2000 » Thu Jul 30, 2020 5:32 pm

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