Dual tanks, without mechanical fuel pump?

[cfan10]

OK, quick question on the dual tank setup on an '84 c10...I am using only the passenger side tank with an external electric fuel pump I would really like t have use of both tanks again. But don't want to go back to the mechanical fuel pump, so my question is can I buy another electric fuel pump and maybe a t-fitting to run to the carb will this possibly work?
I have a new sending unit for the driver's tank, the old one was bad and rather than paying to have it replaced a couple hundred years ago I was given the option to just use the aux/passenger side tank instead.

Thanks in advance for the advice, it is greatly appreciated!

'84 c10 350/350 w/dual tanks

[sweetk30]

i run a tbi tank on left side with tbi sender and 96 c3500 350 vortec spec intank pump no mods just clips in for my efi system needs .

then my pass side tank i just use a stock tbi tank / sender / pump and a toggle switch in the dash to pump it over to the left tank . there is also a red light on the dash just under the radio that lights up when pumping so i dont forget and it cant pump with key off only running .

i tee'd in to the filler neck vent hose and it dumps in the tank just fine . this let me keep it simple stupid and no expensive parts / valves or what not .

[dieseldawg142]

hook your fuel pump up to your fuel line in front of the switching valve instead.
i have an external electric mounted in front of the valve for almost 20 yrs with nary a problem.

[kipps]

If your electric fuel pumps have foot valves, what you describe will work. If one or the other of them does not have a check valve included, you'll be backfeeding fuel through a pump, and filling the opposite tank unawares.

I'm doing something similar with an LS swap. Since I'm using regulators, the possibility of backfeeding the wrong tank is much more real. I'm eliminating the switching valve, and both in-tank pumps are teed together using a shuttle valve. The shuttle valve is simply double outlet check valve. Picture two check valves, but they happen to share the same check ball. This way, either pump and regulator can supply the fuel rail, neither can backfeed to the opposite tank, and when both pumps are shutoff, fuel in the rail does have a route back to the tank if it gets hot and expands. I'm not sure if this last reason is really a factor, but I figured I'd rather be safe than sorry.

[RUN GMC]

Originally Posted by kipps

If your electric fuel pumps have foot valves, what you describe will work. If one or the other of them does not have a check valve included, you'll be backfeeding fuel through a pump, and filling the opposite tank unawares.

I'm doing something similar with an LS swap. Since I'm using regulators, the possibility of backfeeding the wrong tank is much more real. I'm eliminating the switching valve, and both in-tank pumps are teed together using a shuttle valve. The shuttle valve is simply double outlet check valve. Picture two check valves, but they happen to share the same check ball. This way, either pump and regulator can supply the fuel rail, neither can backfeed to the opposite tank, and when both pumps are shutoff, fuel in the rail does have a route back to the tank if it gets hot and expands. I'm not sure if this last reason is really a factor, but I figured I'd rather be safe than sorry.

Can you give us the part numbers and lay out......thanks in advance..........

[kipps]

Two longbed fuel tanks for a '87 chevy -- Rockauto -- Spectra GM1C
Two fuel senders for a '87 chevy -- Rockauto -- Spectra FG05M(left) and FG05N(right)
Six feet(three feet per side) of r9 5/16" fuel injection hose -- ordered on Ebay
Six feet(three feet per side) of r9 3/8" fuel injection hose -- ordered on Ebay

This fuel injection hose was fastened to the senders with ear clamps. No modification is needed of the sending units.

The fuel pumps should be connected to the senders with 3/8" r10 hose. R10 is rated for submersible use. R9 is not. I used ear clamps to fasten the pump to the sender. I think most replacement pumps will come with a few inches of R10 included.

Dorman 5/16" 45-degree quick connect fitting -- 800-122
Dorman 3/8" 45-degree quick connect fitting -- 800-124

These fittings were crimped onto the hoses with ear clamps. I'm not completely happy with these quick connect fittings. They're very difficult to release. I think some other Dorman quick connects would be better.

Corvette filter/regulator -- Wix 33737.

The quick connects snap onto the inlet and return ports on the regulator. The regulator mounts up inside the chassis crossmember under the rear of the cab. It will need some additional support. I haven't gotten to that yet.

All of the above is duplicated side to side. You end up with two regulators tucked inside the cross-member, with their outlets facing each other. Take a Dorman 800-155 3/8"x12" double bead fuel line, and cut it in half. Push each half into the outlet of a regulator. Using a 3/8 compression fitting to 1/4" pipe thread adapter, connect these cut fuel lines to the shuttle valve.

Google "SVB20 shuttle valve" to see the one I'm working with. It looks to be about 45 dollars. It's specified for handling compressed air, but the buna o-rings inside should be fine for gasoline. It can be rebuilt with new o-rings if needed. All three ports are the same size, and should be 1/4" pipe thread, IIRC.

The shuttle valve has one outlet port. I clocked it down a little so I could run a fuel line under the edge of the crossmember, and up toward the fuel rail on the engine.

For that fuel line, I'm using a brass 1/4" pipe thread to 3/8" barbed adapter screwed into the shuttle valve. The nylon fuel line, which is pressed onto the barbed adapter, is Dorman 800-072. This will also be wrapped in split loom to avoid chaffing.

This fuel line is going to be anchored to the underside of the cab floor using some undetermined clips. It will run up to the fuel rail, and clip to that using Dorman 800-082(3/8" straight quick connect).

I'll get some pics once things are a little more together. I got sidetracked on a few other projects for now.

Note that this will not work with stock wiring. You'll want to mount two relays on the firewall, one for each tank. The ecm will send a fuel-pump request voltage to a DPDT switch on the dash, which will switch it between the two relays. The other pole of that DPDT switch will connect the fuel gauge wire to either sender unit. I'm still looking for that perfect DPDT dash switch. I'll include that in a future post when I find it.

Building a fuel system with this method will give the maximum of redundancy. Any part can fail, short of the ECM or the interior switch, and you can still run on one tank.

I mentioned that the regulators need additional support. They come with a bracket that has one bolt hole. This is enough support if they're mounted on a vertical surface. Since I'm mounting them up inside the cross-member, they're on the overhead horizontal surface. Thus, the single mounting bolt is not sufficient. I'm going to make a small "skid-plate" that covers the bottom of that cross-member, and supports the filters from below.

Honestly, I think this is the cleanest method of plumbing two tanks for a LS engine. No obsolete switching valves or expensive AN fittings. Everything is tucked neatly in the cross-member, and is simple to understand with just a glance.