Lotus Elan

Facet Cube Noise

PostPost by: KevJ+2 » Wed Jun 24, 2015 4:08 pm

Hello All,
I have fitted a Facet cube pump and wonder if anyone can confirm that they continue to pump after everything is primed and full. I would have thought you would hear it slow then stop but this thing just keeps on pumping! It's on a rubber mount in the boot (trunk) but still quite clear to hear.
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PostPost by: UAB807F » Wed Jun 24, 2015 4:19 pm

Strangely enough, mine does a similar thing. When I first put it in I expected it to whizz away until the float stopped it and then just give the odd tick until the car started. But unless the delivery is far slower than I expected, it seems to keep pumping away far longer than you'd expect to fill even empty chambers with no apparent drop in speed.

I did wonder if there was an internal relief which allowed it to spin but not push fuel forwards against pressure but as it didn't seem to flood so I just stopped thinking about it and found something else to worry about instead.

( plenty of opportunities there with my car...... :wink: )

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PostPost by: Esprit2 » Wed Jun 24, 2015 6:00 pm

I don't know if this applies to the Elan (I'm a lurker here, I don't own one). Many vintage Britcars/ Eurocars use a small bleed orifice to function as a rudimentary fuel pressure regulator. Europa S1-S2 have one, so the idea isn't foreign to Lotus.

Near the stock Europa pump's outlet is a T-fitting (well, okay, a Y-fitting). The side branch has a very small ID, on the order of 0.012"-0.017". A fuel return line is connected from it back to the fuel tank. During the car's development, the orifice ID is determined such that discharge pressure of the stock pump, located a known/ fixed distance from and below the carb inlet, is reduced to the target pressure at the carb inlet. It's a 'dumb' regulator, and cannot adapt to 'any' non-standard change made to the fuel system.

If a non-standard, higher pressure pump is installed, it can force enough additional flow through the bleed orifice to create sufficient flow that the pump will continue to run noticeably more that it would if the fuel line were a direct connection without a bleed orifice.

Facet cube pumps are available with blue graphics (low pressure) and red graphics (high pressure). The low pressure version should be used for all vintage Lotus applications. If the high pressure version is used, then it definitely requires an aftermarket inline fuel pressure regulator to reduced the line pressure measured at the carb inlet. A bypass type of regulator with a fuel return line will result in the Facet pump running more; and a non-bypass type will result in an occasional click from the pump.

The fuel pump outlet pressure specified in Tech Data is the pump's rating, and the carbs (Z-S, Weber & Dellorto) prefer less at the inlet. The pump pressure generally drops through the length of the fuel line, and as a result of elevation change from the pump to the carb inlet. The carbs like to see a max of 2.5 psi at the inlet (Dellortos & Webers like 1.5 - 2.5 psi).

Regards,
Tim Engel
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PostPost by: UAB807F » Wed Jun 24, 2015 8:26 pm

Hi Tim,

I can't think of a return line on my installation unless it's something internal (valving ?) that I simply can't see. The TC in my Europa doesn't have a return line between the pump & carbs, was it on the Renault or Federal version or has mine just been changed at some point ? It's an old Lotus, nothing would surprise me !

Mine is the 4psi (?) version pump which was supposed to be for carburettor engines, but being nervous about engine bay fires I fitted a regulator in the boot after the pump to hold the pressure down to 2psi just in case of flooding.

I can't honestly say if it stops ticking at any point because once the car's running I can't hear it any more. Do they normally stop ticking on other installations ?

Brian
Last edited by UAB807F on Wed Jun 24, 2015 9:29 pm, edited 1 time in total.
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PostPost by: Elanman99 » Wed Jun 24, 2015 8:45 pm

I have had a Facet pump in the boot of my Elan since about 1970 and can confirm that they never come to a complete standstill.

I think the piston is a rattly fit in the bore and that the limits the pressure it will create. Once the carbs are primed full the pumping rate slows down quite a bit. I only hear the noise when the engine is not running but its quite satisfying to hear when starting the engine because I know when its OK to crank the engine over.

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PostPost by: TroonSprint » Thu Jun 25, 2015 8:20 am

I put a Facet cube pump on an MG Midget 1275 and I also can confirm that it doesn't stop clicking when the float chambers are full. I can also confirm that it's a horrible noisy thing. I have used a Webcon pump on my Elan. This makes a much softer noise, but again doesn't stop when the needle valves are closed, it just gets quieter.

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PostPost by: jono » Thu Jun 25, 2015 4:18 pm

...just changed my Facet cube (it packed in) for one of their modern resign encased ones - much quieter.

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PostPost by: Chancer » Thu Jun 25, 2015 8:59 pm

All Facet pumps but especially the cube one dont like occasional use, their fine if used every day but otherwise will let you down far more than an old AC pump with dirty contacts (we have probably all been there!).

I lost several races and practice sessions due to Facet pumps not to mention the ignomy of being towed back to the pits yet again :(

I swopped for a Webcon and it did what it said on the tin but with complete silence whereas with a Facet complete silence means you will shortly grind to a halt.

All this info is 10 years + old so they may have got their act together since then.
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PostPost by: Galwaylotus » Thu Jun 25, 2015 9:09 pm

Interesting thread. My electric pump (unknown make) used to stop when the float bowls were full but now it doesn't! I would be very guilty of the infrequent use syndrome for various reasons so my current woes (See No Start) may be due to a failing pump! I'll run a few tests for flow and pressure.
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PostPost by: elancoupe » Thu Jun 25, 2015 11:17 pm

Interesting comments - I have been running a Facet cube for almost 25 years without any issues.

Noisy at start up, yes it keeps going after the bowls are full. Almost inaudible on the road, although the raucous exhaust is certainly a contributing factor. :twisted:
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PostPost by: Elanman99 » Fri Jun 26, 2015 9:36 am

Chancer wrote:All Facet pumps but especially the cube one dont like occasional use, their fine if used every day but otherwise will let you down far more than an old AC pump with dirty contacts (we have probably all been there!).

I lost several races and practice sessions due to Facet pumps not to mention the ignomy of being towed back to the pits yet again :(

I swopped for a Webcon and it did what it said on the tin but with complete silence whereas with a Facet complete silence means you will shortly grind to a halt.

All this info is 10 years + old so they may have got their act together since then.


Not sure how you arrive at the conclusion about being unsuitable for occasional use. All fuel pumps are only used occasionally in the sense that they do not run continuously.

The Facet cube type is a simple design with minimal moving parts. As long as it used correctly I would expect it to last forever. The one in my car has now been working since about 1970 in spite of once getting so rusty that I dismantled it and had the casing replated.

Only once did it ever give me trouble and that was because I fitted an aluminium tank which I had done some machining on, Metal filings and swarf were drawn into the pump and caused it to stop several times. I fitted an inlet filter so I can now see how much crud manages to accumulate in a fuel system.

On the issue of noise. When I first fitted the pump I mounted it low down in the nose of the car so it was below the level of petrol in the tank. I was trying to ensure the pump was primed as they are not good at pumping air to draw fuel along a thin inlet pipe. I worked OK but being exposed to the elements got very rusty. It is now 'mounted' in the boot in the cavity to the right of the fuel tank. Mounting in this case being a lump of foam rubber with the pump inside. Its almost inaudible and I only hear it when I start the car inside the garage.

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PostPost by: l10tus » Fri Jun 26, 2015 11:16 am

I purchased a cheap ?8 Chinese copy of the Facet Cube Type pump from Ebay, which failed after 30 mins running time!

I replaced it with the latest 'Round' self priming Facet Posi Flow pump.

The mounting holes are pretty much the same, it will lift up to about 600mm above the tank, is self priming and suitable for intermittent or full time use.

At ?27 incl. post, it's a great bit of kit!

Mine is mounted next to the tank, on a bracket bolted to the bumper retaining bolt, on rubber mounts, and clicks away merrily all the time it's powered up.

It is quieter than the original cube type, but is still audible enough to hear that the carb bowls are full, before engine cranking.

I keep a spare in the boot also ( just in case!)

Regards,

Phil.
Last edited by l10tus on Fri Jun 26, 2015 1:35 pm, edited 1 time in total.
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PostPost by: Chancer » Fri Jun 26, 2015 11:50 am

Elanman99 wrote:
Chancer wrote:


Not sure how you arrive at the conclusion about being unsuitable for occasional use. All fuel pumps are only used occasionally in the sense that they do not run continuously.



Ian, I need to correct what I wrote and apologise, my memory is failing me, I did indeed have a Facet cube pump on my Westfield which whilst very Noisy never packed up in a decade, it was when I bought a Zetec Caterham with the quieter round type pump that all my problems started, it was definitely much better when used every day but could still run for most of a race weekend before deciding to give up on the last race. At the time loads of other owners and competitors had the same problems.

The cylindrical Webcon pump was superb, like I say, 10 years ago and a lot can change in that time.

I think that the cube pumps do oscillate continously although dont make much noise when not pumping, thats probably why they dont suffer the same sticking problems.
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PostPost by: gus » Fri Jun 26, 2015 7:33 pm

electric fuel pumps never stop, but when up against pressure[a closed needle valve] they no longer travel very far if at all on their stroke, effectively shutting up
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PostPost by: KevJ+2 » Sat Jun 27, 2015 3:44 pm

Just thought I'd post the spec for my Cube pump. I guess because it has no positive shut off valve, that's why the little b****er keeps on running.
At 2 - 4psi I'm wondering whether to fit a regulator. At 2psi I probably wouldn't bother but if it runs at 4psi... mmm.
Any thoughts?

Specification:-
Road
Pump:- 40104
Voltage:- 12v
Earth:- Neg
Pressure (Psi):- 2.0-4.0
Flow:- US Gallons/Hr 25
Dry Prime Height in Mtrs:- 0.3
Thread Size:- 1/8th nptf

Positive Shut-Off Valve:- No
Check Valve:- No
Operating Temperature:- -31? F to 55? F (all Models)
Legal Requirements:- Certified & Complies With EEC 95/54 Requirements
Length:- 75mm
Height:- 60mm
Weight:-0.5kg
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