Have to tell you guys...after running EFI now for several thousand mile along with a factory unmodified tank, I can honestly say I'm not having starvation issues even down to say 1/4 tank. Not that I can feel anyway. Even did some datalogs, and fuel pressure is as stable. Now, I'm not road-racing or doing quartermile blasts either - just some casual and spirited driving on the street. Possible that the way my pump is mounted (below the tank - alot lower) is helping it stay primed good.

Not advocating NOT doing anything, just thought I'd pass this along. Still probably going to have the tank sumped, which I know will makes almost perfect for what I'm doing.

I think that makes sense. As long as the inlet strainer stays submerged you'll be fine.

If you wish to be able to run less than 1/4 tank, I don't think the sump will do it. You'll still run the risk of uncovering the pump inlet.

When I create the sump, I wont completely cut the tank to fit the sump...will just drill a ~1" hole in the tank and weld the sump on, so a "pocket" can be created. I think if all the metal is removed from the tank to match the sump, all the fuel will slosh in/out.

For race day (if ever), will use a 1/2 tank.

Not as a sexy a solution as the other options out there, but considering that what I have currently "almost" works as-is, the sump is really the best option.

I agree. Run as deep of sump as practical and route the return line into the sump and you should have an effective low-tech solution.

Currently in the process of having an Edelbrock/Musi 555 EFI retro fitted in my 72 SS along with numerous other changes.(EG: complete rebuild of the front suspension, new "Mosur" 12 bolt rear end, "Strange" driveshaft, complete "HR PARTS and Stuff" rear sway bar and upper/lower control arms, new shocks and Tubo 400 tranny "refresher".)

Regarding the fuel issue I purchased a new tank and added a baffle inside at the back of the tank. The fuel feed(pickup) connection was added also at back of the tank which is attached to a fabricated internal fuel pickup tube with sock mounted into the baffled area of the tank.

The fuel system( feed the monster) will consist of #10AN lines from the tank to the fuel rail regulator utilizing the current 3/8 feed line as the return line.

The external electric fuel pump is preceded by a #10 AN inlet /outlet fuel filter with the lines following the passenger side frame to the back side of the motor.

I think this configuration will eliminate any fuel issues as the vehicle will be used for the occasional " strip trip", notwithstanding it's generally anticipated mostly street usage.

The project isn't yet finished per se but I'm looking forward to full completion/testing and final setup by the end of this month.

Why not run a low pressure pump from the main tank to a small secondary tank with a return line so that the secondary tank is always full. Run the high pressure pump off of this tank to the engine. No chance of the pick up becoming uncovered. I believe VW may have used this idea. Seems simple enough to me. I have a '94 LT1 that I plan on running this way some day.

The thought of running two electric pumps just bothers me. Although, that option is still on the table.

Why not run a low pressure pump from the main tank to a small secondary tank with a return line so that the secondary tank is always full.

The Marine industry has done this for decades. The secondary tank is called a vapor separator. On my Yamaha HPDI, two vacuum operated diaphragm pumps transfer fuel from the main tank to the vapor separator. A submersible electric pump (50 psi) transfers fuel to a belt-driven mechanical pump. The mechanical bumps pressure to 750 psi for delivery to the injectors.

In total, it runs four fuel pumps and four fuel filters and is considered one of the better running and most reliable 2-strokes ever made.

I think using a rotary vane style electric pump (Carter) to transfer fuel from the tank to the separator would be very reliable. I'm sure a custom-fabbed vapor separator could be designed with a submersible pump, or just use an empty can with an external high-pressure pump.

The Marine industry has done this for decades. The secondary tank is called a vapor separator. On my Yamaha HPDI, two vacuum operated diaphragm pumps transfer fuel from the main tank to the vapor separator. A submersible electric pump (50 psi) transfers fuel to a belt-driven mechanical pump. The mechanical bumps pressure to 750 psi for delivery to the injectors.

In total, it runs four fuel pumps and four fuel filters and is considered one of the better running and most reliable 2-strokes ever made.

I think using a rotary vane style electric pump (Carter) to transfer fuel from the tank to the separator would be very reliable. I'm sure a custom-fabbed vapor separator could be designed with a submersible pump, or just use an empty can with an external high-pressure pump.

Interesting. Sounds like you can even run a stock engine driven mechanical pump and have a small fuel cell in the front with the electric high pressure pump fully submerged. Any reason why that wouldn't work?

Andrew

That would technically work. The marine vapor separator has a float and needle & seat assembly to maintain the fuel level. You'd either have to do this or install a return fuel line to the fuel tank.

In the event of a crash, I don't really care for having an additional container of fuel under the hood.

Pro-touring guys run this type of setup all the time. One very popular combo uses a tall cylindrical tank with the efi pump, the tank is fed by a standard low pressure pump and has a return line at the top of the tank going back to the main fuel tank. The EFI return line returns to the "surge" tank. Some guys even use Home Depot water filter housings.

I was thinking of doing the surge tank and just could not find a place to mount it under the car. I actually went as far as buying a canister fuel filter and modifying it so it had a lower point within the canister for the fuel outflow to the electric pump. This was actually a really nice setup and I still have it but there is just no way to mount it under the car even with it being fairly small. I would guess you could do it but it would take some modifying of the floor pan or just attaching it to the frame as close to the floor as possible. It also could be mounted in the engine bay, but I was worried about the fuel being heated. In the end I went ahead and just ran the stock tank and I have been down to about 1/8 tank with no issues. Granted I dont jump on it when I am heading to the gas station it seems to make it fine. The fuel canister I picked up was a Mallory canister and the nice thing about it is it has 2 inlets and two outlets for fuel hookups. They are I believe 6 or 8an fittings. I think this would solve the starvation problem but does require two pumps. You also don't need to use two electric pumps. You can hook up the stock manual low psi pump to the inflow side and the electric pump to the feed for the throttle body if running two electric pumps sounds like a hassle.

I just welded a bung into the tank for a 1/4 NPT to -6AN for the return line and bought a 3/8" out sending unit. Hopefully it will work fine with the FAST system for a crusier. The fuel pump is mounted below the tank level so that should help.

That's basically what I did with mine and haven't had a problem yet. I just put the return line on the sender and had a guy weld it in. Cost me $20 dollars since I don't have a welder but hey it works. Of course it would be nice to have an EFI tank but who wants to pay $1200 for one when this seems to work fine. Maybe down the line if I have any issues with my current one but we'll see.

Although a Nova...I did similar mods to the fuel sender (equal sized return line pointed away from the pickup and bent the pickup a tad closer to the bottom of the tank). 14,000 miles with no ills effects. I have felt times when the pickup is uncovered...time to refuel. Always drag full though.

Tim