EFI with 3 fuel tanks?

[bronco italiano]

-So I am prepping to convert my buddy's bronco to SEFI. He insists on having the 23gal main and 2 saddle tanks.
-I have the Carter LP pump that will be plumbed in behind the driver seat, go to the accumulator, and an Ext HP pump in the engine compartment.
-My buddy insists on retaining the factory fuel tank valve so I found an very high quality Airplane fuel valve with positions for 3 tanks.

My main concern is I have to plumb the tanks to the valve and then to the LP fuel pump and not sure if the LP pump will tolerate that configuration.
Thank you in advance.
BI

 

[Steve83]

...retaining the factory fuel tank valve so I found an very high quality Airplane fuel valve with positions for 3 tanks.

Why would you need that if you have to use the original tank valve? You can't use both valves.

...not sure if the LP pump will tolerate that configuration.

It doesn't care how many possible positions the tank valve(s) have - it only cares that there's somewhere it can pull fuel from.

But you don't have to use any mechanical valve - you can use electrically-operated valves. What is he planning to do about the fuel gauge? Does he want a level sender in the 3rd tank?

 

[Broncobowsher]

The LP pump won't care. That Carter just works.

The rest of the plumbing gets interesting. I know of the 3-way selector valve, they also use them on boats. But what is your plan for the return line?
The supply plan looks pretty good. The EFI will return to the accumulator. But that carter feeding the accumulator needs a bleed off back into the supply tank. Without it there will be an extra 5-7 PSI of backpressure on the EFI system and that will raise the EFI fuel pressure. There is also an issue of the accumulator getting air locked. Any gulp of air that the Carter picks up will be placed into the accumulator and will have no place to go. Eventually the accumulator will be full of mostly air and the EFI pump will have to start sucking that. The only way out of that system is through an injector. EFI engines don't run happy squirting air instead of fuel.

 

[bronco italiano]

Thanks for the info. The plan, subject to change (like a Q-jet) was to:
1- Plumb the lines through the tank selector valve, run a return to the main, which has an elevated 1 qt overflow vent-tank.
Or
2- Run all 3 tanks together with no tank selector with a return to the main since it sits highest of the 3.
Or
3- Through my hands up and get a nice Q-jet built and bolt it on with the Carter LP pump to a filter with return line to main tank.

I need simple and most reliable as I will be 3k miles away from my buddy when he has problems, but I am sure there are some awesome Bronco guys in SW Tenn.
Thanks, BI

 

[DirtDonk]

As said, don’t run a return line to just one tank.
As long as the engine is running fuel is being pumped into that one tank and will quickly overfill it. In fact, while sitting at idle at a traffic light, you’re probably returning more fuel than the engine is actually using.
It could get ugly and messy very quickly.

And what do you mean by one tank has an elevated 1 quart overflow? What kind of a set up is this?
You’re not talking about the factory vapor recovery tank are you? If so, than the very last thing you would ever want to do, meaning you never want to do it, would be to pump excess fuel into that tank inside the cabin, and then have it overflow into the charcoal canister.
As said, ugly and messy. But add stinky too!

 

[bronco italiano]

Thanks DirtDonk. I made annoverglow tank because my buddy had unvented fuel caps and in the Stockton heat his main tank would leak. I plumbed a canister under the bed rail with an overflow vent (all on the opposite site of the exhaust pipes). Not a big deal to do a 3 tank return if that is what it takes.

 

[DirtDonk]

Seems like it would just be easier to plumb another valve to route the return fuel to the tank that it’s being used from.

 

[bronco italiano]

Makes sense

 

[bronco italiano]

Does anyone make an electrical tank switch with return ports for a 3 tank setup?

 

[DirtDonk]

There used to be one, but I usually see only the two tank version these days. Search “Pollock“ and see what you come up with.
I think that’s how it’s spelled anyway

 

[bronco italiano]

Thanks DD

 

[Oldtimer]

Pollak Fuel Tank Selector Valve​

It appears the only option is for two tanks (6 port valve).
For three tanks you will need two valves.
First valve would select main or aux TANKS.
Second valve would select aux1 or aux2, and feed it to first valve.

 

[bronco italiano]

Nothing like wisdom from an Old-timer!!! Thank you. What if I tied aux 1 and aux 2 together to a LP fuel pump to a switch to just feed the main tank when it gets low? Trying to be as simple as possible. Then I could just have 1 return line to main.

 

[DirtDonk]

A lot of people link an auxiliary tank (or tanks in this case) into feeders for the main tank
You just have to be careful not to overfill the tank is about the only short coming I believe.
Maybe search for some threads with the terms “transfer tank“ in the subject.

 

[bronco italiano]

Couldn't find much of any information searching "transfer tank". Is there a special type of pump to shift the fuel from the auxiliary tanks to the main?

 

[DirtDonk]

Sorry, maybe "transfer pump" instead? Using google instead of the search button up top in case that's what you were doing.
I think one of the main go-to pumps has been the Carter P4050 (I think that's it's number) that has been around for many decades in pretty much the same form. Seems like they changed it a bit a few years ago though. Probably when things really started going overseas exclusively?

Anyway, someone will jump in with the exact info. I'm just shooting from the hip.

paul

 

[Broncobowsher]

P4070 is the go to Carter pump.
Yes, a transfer pump is an option. But not something for general use. So easy to keep filling an already full tank and it just overflows. You really have to stay on top of the fuel tank selection valves. Way more than a normal multi tank setup.

 

[bronco italiano]

Thanks gentlemen. I saw a Carter P4600HP pump for about 2x the costs of the P4070. Is that a special pump or something? Yes my concern is the transfer and overfill by forgetting to shut off the transfer pump power.

 

[El Kabong]

Thanks gentlemen. I saw a Carter P4600HP pump for about 2x the costs of the P4070. Is that a special pump or something? Yes my concern is the transfer and overfill by forgetting to shut off the transfer pump power.

Looking at their specs, both are rated at 50gph, but the p4600hp has 3/8 npt in & out vs 1/4 npt on the p4070. Reading thru the q&a it looks like the p4600hp works well on high hp applications, while they don't answer that directly for the p4070.

I've used p4070s for years & am happy with them. Prior to swapping over I had tried some Holleys & had trouble with them failing in the rain.

 

[bronco italiano]

Thanks. I have the 4070 on my bronco and love it.