efi fuel system idea...will it work?

[oldiron]

I have dual tanks in my '74. What I want to do is keep the factory selector valve under the drivers seat (putting this valve in between tanks has kept it from being stolen twice). Question is can I... use the stock mechanical fuel pump as the low pressure pump and run the return line from the fuel rail back to the pickup side of the stock pump or new high pressure pump. Has this been tried yet? Seems like this would eliminate the need for running return line to two seperate tanks and using a 6 port switch to keep it all going to the right tanks.
Ideas???
Greg

 

[beaubronco]

Great idea on the anti theft

 

[Broncobowsher]

Not real well.

Part of the return line is for cooling. cool fuel to the injectors, the pump is cooled by fuel moving through it. Without a return line there is some cooking fuel issues that can creep up on you.

Another is without a return line you will have excessive pressure on the return line. Figuring your plan is to loop the return back to the EFI pump and Tee in a supply from the mechanical pump at the same place. that will keep an extra 6PSI in the whole return line.

Now it should go together, run and drive the way you want it to. But vapro lock issues and other odd fuel delivery issues at possible random times can be expected as well. There are little gremlins like when the fuel pump taks a gulp of air, how is that purged from the system without a return line? In a carb it is purged via the fuel bowl. Typical EFI is is returned to the tank. Modern EFI they use baffles and chambers to keep the air bubble away from the pump. Your system it would have to pass through the injectors to get out.

With my last EFI I kept the stock selector valve but got away with a single return only to the main tank. It did require you to drive on the main tank first, when that went low switch to the aux. The return line would transfer the gas back to the main and partially fill it again. When the aux quickly went low, switch back to the partially filled main.

 

[oldiron]

I wasn't thinking about the whole air purge part of the equation, I had planned on using a "cool can" to take care of the fuel cooling issue.
I'll probably just run one return to the main tank and use the aux, pumps,return as a transfer pump for the rear tank.
Greg

 

[elkarcher]

I have dual tanks in my '74. What I want to do is keep the factory selector valve under the drivers seat (putting this valve in between tanks has kept it from being stolen twice). Question is can I... use the stock mechanical fuel pump as the low pressure pump Greg

Someone is doing this. I cant remember who it is. As far as i know it works.

 

[1sicbronconut]

Kind of hard to find but a 6 way selector from 73' only would work perfect for you.

 

[DirtDonk]

I think you can still find them in Grainger and McMaster/Carr catalogs.

Paul

 

[73azbronco]

I just bought a 6 way from WH or BC, can't remember which.

It will work, but the cost and time of running another line back to the overflow line of the rear tank is just to easy to "do it right" rather than tempt fate with a "no return" line used in much later models.

 

[justinkwitt]

btw, pollak makes a kit 42-300 or 42-300P which has the valve a new switch and wiring and everything. i think its the same one that online vendors sell. you should be able to find em at your local parts store or truck/tractor place (last i ck'd we have 12 in stock). do that and add an additional switch in the glove box or under the dash (or even down in the original tank selector hole) for your ignition or fuel pump relay and you have just as good security plus its all updated and done correctly. the kit should run between $75-95. I believe the jobber price is like $82.

btw, for the people with door jamb switches for lights and alarms, pollak makes the pigtails and they retail for $6 which beats O'reillys o'crappy price of about 30 bucks for the motorcraft ones. part number 52-622. they are in the pollak catalog, but they dont have an application look up. sorry, dont mean to try and steal the thread.

 

[Broncobowsher]

Someone is doing this. I cant remember who it is. As far as i know it works.

I thought that person was doing it with a float bowl off a holley carb attached to an accumulater and the high pressure circulating through the accumulater. So it is a carb setup to the fuel bowl and EFI accumulater loop on the other side.