EFI return - dual independent fuel tanks

Julian

Lifetime Supporter
Anyone have experience installing an EFI system with draw and return to dual independent fuel tanks? If so, any information on valving, line routing etc. to make it work would be most appreciated. I would prefer an option that is a flick of a switch as opposed to cranking manual valves.

Thanks,
 

Ian Anderson

Lifetime Supporter
Hi Julian

Try a search for 6way Pollack Valve

It will give you a pile of information

You need the 6 way
2 tanks to 1 outlet to swirl pot = 3 connectoins
Return to 2 tanks = 3 connectoins

When you click the switch it moves a solenoid and changes both the draw from and return to tank arrangement at the same time

Ian
 

Ian Clark

Supporter
Hi Julian,

There's been discussion in threads before about twin tanks, plumbing etc. It can get intense because there are so many variables including packaging, surge tank (or not), size of fuel lines required, safe layout of all components, sevicability after completionand so on.

You are heading done the most challenging road of any GT40 build. I'm sure a lot of good information will be shared.

Having done a couple of EFI systems on CAVs, both work very well yet I'd still do it different next time. If I had the luxury of designing the entire system prior to build, I'd go with a balance pipe between the tanks, with a single pump and fuel pressure regulator located in a surge tank within one of the two tanks. Then you have no return lines, no switching valves, one pump, one fuel line output, no exposed surge tank, a huge saving in plumbing hardware and much tidier engine bay. Just my 2c worth.

Of course you have to work within the layout and major components in your car. With good planning and a few dry runs, you'll have a reliable, servicable system. So bring it on, let's see these systems are being done!

Cheers
 
HI Julian The system that I thought was neat was they installed a carb float asm. in the surge tank, NO return needed. Just sellect Pump right or Pump left and the float asm maintanes the level in the tank for the EFI pump.
 

Ron Earp

Admin
Just scroll down to the bottom of this page and look at what the search engine has automatically found for you based on your thread topic. Listed there in "Similar Threads".
 

Ian Anderson

Lifetime Supporter
Wally

That system sounds good but I can see one potential flaw

On your described system the HP system would be Swirl to pump to fuel rail to overflow back to swirl

Now an EFI pump pushes a load of fuel and generates quite an amount of heat that is carried back the the fuel tank in normal operation the fuel in the tank acts as a heat shunt. In some cars the return even goes through a small cooler / radiator to reduce the heat flowing back to the tank.

So on your system the hot fuel would never return to the tank and the fuel in the swirl pot would get very warm. This would happen most with the car at rest or in slow traffic.

Not saying it's wrong just suggesting there are potentially other ways to do the same thing and overcome the problem

I also agree that if I was doing things over I would have the tanks connected and only run one feed and return

Ian
 
That looks similar to what I have done, but I don't have it working yet. I have pumps in each tank that feed to a swirl tank. From there I have a main pump that supplies the rails. The pressure regulator sends the fuel back to the swirl tank. The return on the swirl tank goes through a solenoid operated valve. When the pump in the driver's tank is on, the valve sends the fuel back there. When the passenger tank pump is on, the fuel goes back to that tank.

There are valves in both in-tank pumps that keep the fuel from flowing back into the tank when the pump is off. There is also a 5 psi backpressure valve in before the solenoid valve that keeps pressure in the swirl tank.
 
I used a duplex fuel valve like they use on aircraft. the valve switches both the fuel supply and fuel return to the same tank at the same time.
 

Ian Anderson

Lifetime Supporter
I run 1 low pressure pump and 1 HP pump and 1 fuel switch over unit

So system is

Tank - pollack valve - filter - LP pump - swirl pot
Return from swirl pot - Pollack valve - tank

Then Swirl - HP pump - fuel rail
Pressure valve on rail - swirl pot

So the change over does that and only 2 pumps are needed
The 2pole 2 throw switch that does the change over also selects the gauge sender for the relevant tank

The fuel pumps run for 3 seconds when ignition is turned on to prime system then stop, crank the engine and the pumps both start again and will run unless engine stalls when after 3 seconds they stop (Timing is through the Rover EFi brain and relays)

3 pumps builds in some redundancy, however the final engine feed is the HP pump and you only have one of them! (Unless you ae anal like me and carry a spare everywhere!)

Ian
 
HI All after talking with the owner of the car this system is on. It uses a returnless fuel pump and does not recirculate the fuel back to the reservoir. So he is not worried about heat build up in this system. Sorry for not checking this out closer before posting.
 

Julian

Lifetime Supporter
Thanks guys, armed with the information provided I have a way forward.

Turns out I have a swirl tank sat on a shelf from an old Kinsler mechanical FI that is ideal for the duty. I will plumb the existing low pressure pumps to it and run a high pressure pump from there with fuel return lines switched through a Pollack valve to each tank.

This has been a great help, thanks again.

I wish the search engine could be as capable of narrowing down the similar threads, my prior search brought up 10 pages of mostly unrelated garbage.
 
I see Wally beat me to my point. Many US cars (and maybe others) now have a returnless EFI system (multiport only). The pressure regulator is in the pump, which is in the tank; thus the "return" is also in the tank. Therefore, all you need for a dual-tank setup is to put a check valve in each supply line from the tank and then tee into a single line to supply the fuel rail. The check valve is required to keep from pumping fuel into the "dormant" tank. It would seem to me that this is by far easiest solution if you are going to run EFI on a dual-tank setup, although you would still need two fuel gauges.

Eric
 

GTPVette

Supporter
That looks similar to what I have done, but I don't have it working yet. I have pumps in each tank that feed to a swirl tank. From there I have a main pump that supplies the rails. The pressure regulator sends the fuel back to the swirl tank. The return on the swirl tank goes through a solenoid operated valve. When the pump in the driver's tank is on, the valve sends the fuel back there. When the passenger tank pump is on, the fuel goes back to that tank.

There are valves in both in-tank pumps that keep the fuel from flowing back into the tank when the pump is off. There is also a 5 psi backpressure valve in before the solenoid valve that keeps pressure in the swirl tank.

What type of valve are you using down stream of the swirl tank??

Thanks
Fred
 
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