Fuel pump alternative

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Discussion

100SRV

Original Poster:

2,126 posts

241 months

Saturday 25th October 2014
quotequote all
Hi,
I use a Facet solid-state fuel pump on my truck, this feeds a swirl pot in the front (about 2 metres away and 0.5 metres higher. The pump is situated below the bottom of the fuel tank so is gravity fed, a pre-filter is used (see seperate recent thread!).

The swirl pot is used to keep all the EFi stuff at the front of the car.

The primary problem is that the pumps seem to have a short working life, anything from 5000 miles to a few years. My perception of "short life" is based on the knowledge that I've never replaced a fuel pump on other cars I've owned.

Is there a more reliable alternative to the Facet interrupter?

cheers
100SRV


99hjhm

426 posts

185 months

Saturday 25th October 2014
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What's engine is it feeding? Guessing it's nothing massive as the solid state facets don't have much puff?

100SRV

Original Poster:

2,126 posts

241 months

Saturday 25th October 2014
quotequote all
Hi,
feeds a swirl pot which feeds a Rover 3.9 V8 running 14CUX EFi

I'm using a facet solid state "fast road" spec.

cheers,
100SRV

DrDeAtH

3,586 posts

231 months

Saturday 25th October 2014
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Holley 'red' pump should do it. Not the quietest of pumps though.

paintman

7,669 posts

189 months

Saturday 25th October 2014
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Change or modify the tank & use a Range Rover Classic in-tank pump?

Steve_D

13,737 posts

257 months

Sunday 26th October 2014
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Am I missing something here?
There should be a low pressure lift pump supplying the swirl pot and a high pressure pump below the swirl feeding the EFI.

You only mention one pump...if this is the case then the swirl pot is pointless.

Steve

ETA Should have also asked what size pipes you are using. High pressure pumps do not like sucking so the supply pipe should be getting on for twice the size of the outlet. If not then cavitation can occur which can kill a pump...thinks?

Edited by Steve_D on Sunday 26th October 09:33

100SRV

Original Poster:

2,126 posts

241 months

Sunday 26th October 2014
quotequote all
Steve_D said:
Am I missing something here?
There should be a low pressure lift pump supplying the swirl pot and a high pressure pump below the swirl feeding the EFI.

You only mention one pump...if this is the case then the swirl pot is pointless.

Steve

ETA Should have also asked what size pipes you are using. High pressure pumps do not like sucking so the supply pipe should be getting on for twice the size of the outlet. If not then cavitation can occur which can kill a pump...thinks?

Edited by Steve_D on Sunday 26th October 09:33
There is a high pressure EFi pump below the swirl pot fed by a 10mm hose. I didn't mention this because the HP pump hasn't caused any problems.

Steve_D

13,737 posts

257 months

Sunday 26th October 2014
quotequote all
100SRV said:
There is a high pressure EFi pump below the swirl pot fed by a 10mm hose. I didn't mention this because the HP pump hasn't caused any problems.
OK so which pump is it... red top, Silver top road, Silver top competition?

Perhaps not relevant.....These pumps are self regulating and designed for carbs. In this mode they pump the carb up to 6psi and keep pumping away at that load. In your case i'm assuming you have a return to the tank from the top of the swirl. If this is the case then your pump will not be under load and will in effect be 'over reving'.

The only reason you have a return to the tank is to clear any air that could build up in the swirl. To resolve this put a restriction in the return line such that there is barely more than a dribble passing back to the tank. This will be enough to clear the air.

An added bonus is that your swirl will be putting 6psi on the inlet to your high pressure pump which will go some way to eliminating possible cavitation at the inlet of the HP pump.

Steve

100SRV

Original Poster:

2,126 posts

241 months

Sunday 26th October 2014
quotequote all
Hi Steve,
Solid state to fast road spec. Good point about the restrictor, I used to have one in the return line when running the engine with twin SU carburetters, I'll reinstate it in the swirl pot to tank line.

Thought there had to be a simple solution / installation error.
I'll check the delivery rates for the lift (problem) pump and the EFi pump to be sure the lift pump can keep up.

Thank you for the advice, always appreciate a second, more experienced point of view.

100SRV

fatjon

2,144 posts

212 months

Monday 27th October 2014
quotequote all
This setup is a sure way to kill the high pressure pump. It draws fuel from the swirl pot, feeds it round the injector rail and returns it to the swirl pot. The vast majority returns to the swirl pot getting hotter on each cycle. Eventually the fuel is so hot that it kills the HP pump either by overheating or by trying to pump vapour. You need a tank return from the top of the swirl pot so cool fuel is cycled through the swirl pot by the low pressure pump and no vapour accumulates.


100SRV

Original Poster:

2,126 posts

241 months

Monday 27th October 2014
quotequote all
Hi,
OK, getting a bit more complicated now. The recirculation of the fuel is a bit of a problem in hot weather so I can see the need to return the rail to the tank.

Present arrangement is:


StevieTurbo proposes a restrictor in the return line to make the lift pump work:



The lift pump is rated:
7.0-4.0 PSI @ 145 litres or 32 gallons per hour

The EFi pump is rated:
2.54 KGF / cm3 43.25 lbs / square inch or 3 bar @ 150 litres or 33 gallons per hour

The lift pump is just shy of the HP pump by 5 litres/hour, I'd be amazed if I ever spend more than 30 seconds at WOT so the deficit can be ignored.

What should I do?
Send the fuel rail return direct to tank and restrict the swirl pot return to tank...
The spare port on the swirl pot can then be blanked and I spend 0 hours worrying about the demise of a fuel pump.

The above can be achieved by teeing the rail return into the tank return line AFTER the swirl pot exit restrictor. This means high volume flow rate returns to the tank to mix and cool while the lift pump has to do some work.

Thank you for the education!
100SRV


andy-xr

13,204 posts

203 months

Monday 27th October 2014
quotequote all
When I had twin 40s on my car I put a silver top and a regulator on, with a gauge on the regulator so I could measure the flow rate. I preferred that than going for the smaller electric pumps as they burned out.

On my EFi setup I've got an injection tank, so swirl pot built in. Other people with similar setups have welded the tank to fit one, some others dont bother and just dont go below 1/4 tank. But the main pump for the EFi is a Sytec inline pump after the swirl pot, it's mounted just ahead of the tank. There's a pre installed regulator at the fuel rail for mine so I know it's set to 2.5 bar

Here's the one I have: http://www.ebay.co.uk/itm/SYTEC-MOTORSPORT-IN-LINE...

100SRV

Original Poster:

2,126 posts

241 months

Monday 27th October 2014
quotequote all
andy-xr said:
When I had twin 40s on my car I put a silver top and a regulator on, with a gauge on the regulator so I could measure the flow rate. I preferred that than going for the smaller electric pumps as they burned out.

On my EFi setup I've got an injection tank, so swirl pot built in. Other people with similar setups have welded the tank to fit one, some others dont bother and just dont go below 1/4 tank. But the main pump for the EFi is a Sytec inline pump after the swirl pot, it's mounted just ahead of the tank. There's a pre installed regulator at the fuel rail for mine so I know it's set to 2.5 bar

Here's the one I have: http://www.ebay.co.uk/itm/SYTEC-MOTORSPORT-IN-LINE...
Thank you Andy,
the design of the tank and nature of vehicle use (severe gradients pitch and roll) mean that I prefer to use a swirl pot topped up by a LP pump. The vehicle often spends tens of minutes operating at roll angles up to 40 degrees and similar in pitch.
100SRV

100SRV

Original Poster:

2,126 posts

241 months

Wednesday 29th October 2014
quotequote all
fatjon said:
This setup is a sure way to kill the high pressure pump. It draws fuel from the swirl pot, feeds it round the injector rail and returns it to the swirl pot. The vast majority returns to the swirl pot getting hotter on each cycle. Eventually the fuel is so hot that it kills the HP pump either by overheating or by trying to pump vapour. You need a tank return from the top of the swirl pot so cool fuel is cycled through the swirl pot by the low pressure pump and no vapour accumulates.
Hi fatjon,
having discussed this with a colleague last night I'm going to reject this as a red-herring. Why?

The HP pump has a flow rate of 149 LPH
The LP pump has a flow rate of 145 LPH
Swirl pot capacity is 1 litre

Most of the vehicle's use is with less than 60% engine power being used so the rate of return from the swirl pot will be quite high (perhaps around 60% of that pumped to the fuel rail).

This gives 89.4 LPH into the swirl pot with a further 145 LPH contributed by the LP pump - 234.5 LPH of which 233.5 will have to go back to the tank via the return line.

The tank has a capacity of 62 litres - over the course of a few hour's driving / green laning all of this will have passed through the fuel rail at some point so the net temperature will increase. The tank is stainless and has a large surface area so I would expect this to dissipate heat quite well.

Any more suggestions on the fuel pump?

100SRV



anonymous-user

53 months

Wednesday 29th October 2014
quotequote all
100SRV said:
Hi fatjon,
having discussed this with a colleague last night I'm going to reject this as a red-herring. Why?

The HP pump has a flow rate of 149 LPH
The LP pump has a flow rate of 145 LPH
Swirl pot capacity is 1 litre

Most of the vehicle's use is with less than 60% engine power being used so the rate of return from the swirl pot will be quite high (perhaps around 60% of that pumped to the fuel rail).

This gives 89.4 LPH into the swirl pot with a further 145 LPH contributed by the LP pump - 234.5 LPH of which 233.5 will have to go back to the tank via the return line.

The tank has a capacity of 62 litres - over the course of a few hour's driving / green laning all of this will have passed through the fuel rail at some point so the net temperature will increase. The tank is stainless and has a large surface area so I would expect this to dissipate heat quite well.

Any more suggestions on the fuel pump?

100SRV
You need to check your maths! Currently, your tank would fill up and overflow!!

(hint, some of the fuel the LP pump moves to the swirl pot is also the same as the fuel "going round in circles" via the HP pump)

100SRV

Original Poster:

2,126 posts

241 months

Wednesday 29th October 2014
quotequote all
Max_Torque said:
You need to check your maths! Currently, your tank would fill up and overflow!!

(hint, some of the fuel the LP pump moves to the swirl pot is also the same as the fuel "going round in circles" via the HP pump)
Hi Max Torque,
I was checking my maths using a spreadsheet but got myself confused ;-) so gave up until this evening.
100SRV

100SRV

Original Poster:

2,126 posts

241 months

Monday 3rd November 2014
quotequote all
Bump...any proposals for a fuel pump?

226bhp

10,203 posts

127 months

Monday 3rd November 2014
quotequote all
100SRV said:
OK, getting a bit more complicated now.
Certainly is, why not simplify it?
HP pump from tank, to inline fuel filter, to fuel rail, excess fuel back to tank.

??

RC Developments

83 posts

123 months

Monday 3rd November 2014
quotequote all
100SRV said:
Bump...any proposals for a fuel pump?
Have had problems with the Facet pumps in the past, try changing to a Holley pump or fit a small walbro high pressure pump in tank to feed the swirl pot. In tank will help keep the pump cool and if well baffled will prevent the possibility of the pump running dry.

Either way I would return the fuel from the rail back into the tank and not the swirl pot.

Steve_D

13,737 posts

257 months

Monday 3rd November 2014
quotequote all
226bhp said:
100SRV said:
OK, getting a bit more complicated now.
Certainly is, why not simplify it?
HP pump from tank, to inline fuel filter, to fuel rail, excess fuel back to tank.

??
As has been said the vehicle is off-road comp and can spend quite a time at silly angles hense the use of a swirl/surge tank.

Steve