(INTAKE) EFI-prepping a 1st gen
 

I've been running an injected 1st gen for a few years now, and thought I'd summarize my fuel system mods to incorporate an in-tank pump. I previously ran with two pumps and an external surge tank. The noise of the two pumps combined with the multitude of potential leak points convinced me to switch over. Many thanks to Steve84GS_TII for inspiration. The tank mods were well worth the effort, and likely less work than the initial setup of the surge tank.

Adapting an FC In-tank Pump to SA Tank

An FC fuel pump assembly, mounting flange, and slosh cup were scavenged from a tank at the auto wreckers. Tanks are already cut open to drain fuel when a wreck comes in, so the tanks are scrap value only.

The parts as removed can be seen below:

https://www.rx7club.com/attachment.p...d=195717&stc=1

To start the swap, the stock SA fuel tank was drained and removed. To expell any remaining fuel, the tank was flushed repeatedly with water, then washed inside with dishsoap and water. Use extreme caution when working on fuel system components!!!

On the SA tank there is only one location where there is enough space to mount the FC flange. The mounting area was sand-prepped and then the cutout marked with a Sharpie. See pic below:

https://www.rx7club.com/attachment.p...d=195719&stc=1

The FC flange was prepared for rivet mounting by drilling and countersinking eight 1/8" dia. holes around the perimeter of the mounting flange between the already existing threaded holes that the pump assembly fastens to. About 1/8" of the lip of the tank opening can then be carefully bend upwards to mate nicely with the FC flange. Once the flange was fit nicely to the tank, the rivet holes were drilled through the tank using the flange as a guide. Clecos were used to hold the flange in place to ensure all holes matched. Rivets or suitable screws could be placed in the holes temporarily as well if clecos aren't available. Be sure to clean any chips from the tank periodically during this process.

https://www.rx7club.com/attachment.p...d=195722&stc=1

Now the tank is ready for the flange, but it should not be mounted yet. The slosh cup needs to be fit to the inside of the tank first. The stock slosh cup won't fit into the hole in the tank. To fit, it needs to be trimmed down about 1" in height. Had the mounting flange already been fit, it would need to be trimmed even farther, as the flange has a slightly smaller opening than the tank hole.

https://www.rx7club.com/attachment.p...d=195723&stc=1

The stock internal baffles within the tank needed to be bent forward slightly to make room for the slosh cup. The next pic in sequence shows the baffle 'tweaking' needed. The slosh cup location was finalized by trial-fitting the pump assembly and checking for clearance with the return tube and pump pickup. Two 3/16" dia. rivets were used to fasten the cup into the tank. To seal these rivets, a small amount of metal-filled epoxy (JB-weld) was placed around the rivet, and at the interface between the cup and bottom of the tank.

The tank flange can now be mounted by applying a small continuous bead of JB-Weld around the mounting flange, and riveting with 1/8" rivets. Be sure to clean any JB-Weld out the pump mounting screw holes (those 8 threaded holes in the flange) prior to it curing!

https://www.rx7club.com/attachment.p...d=195724&stc=1

Cap or crimp/braze the original fuel supply and return lines shut on the tank. Prior to final assembly, be sure to wash out the tank, and remove any contaminants that remain.

Drop in the FC pump assembly, and wire it up. Depending on pump type used, new pump wiring may be needed. To power the Bosch pump in this install, a dedicated 12 ga. feed was run from the fuel pump relay.

The final assembly looks like this:

https://www.rx7club.com/attachment.p...d=195727&stc=1

Sorry but no pics were taken after the final cleaning and painting of the tank. Access to the lines on the top of the fuel tank is impossible once the tank is mounted, so run sections of line from the supply and return lines first.

During this swap the stock return line was removed, and replaced with a 3/8" steel equivalent. It now serves as the supply, with the old 5/16" being used as the return. An in-line fuel filter (NAPA 23481, GF1481) was mounted where the stock external fuel pump used to be located. This fuel filter is a very popular unit, costs around $10, and is used on oem installations up to 360hp.

https://www.rx7club.com/attachment.p...d=195732&stc=1

This filter uses the std GM o-ring type fittings, which can be adapted to hose by purchasing a 'Fuel Line Repair Kit'. These repair kits come in different lengths.

https://www.rx7club.com/attachment.p...d=195733&stc=1

A 24inch long version can be used to replace the existing supply tube that mounts to the underbody in the axle area, connecting via hose to the fuel pump outlet on the one end, and threading directly into the filter on the other end.

Last couple pics:

Nice work..

What's the small tube next to the fuel pickup?

The one on the pump assembly? That's the return line. It runs right down near the bottom of the tank as well, to eliminate splashing of fuel on return.

I should also say I've tossed the car around heavily with the tank on 'E', and have not experienced any fuel supply problems.

I meant the really small tube with the block on the end.

Oh, that's the fuel level sending unit. It's all one integral unit to keep the number of tank connections to a minimum. I checked the FSM, and the resistance range of the FC unit is identical to the 1st gen cars, so it should work fine. I haven't bothered wiring it up, though. It's just along for the ride.

There's also a low-level sensor that hangs down beside the pump as well. This would be a nice addition, perhaps driving an LED tucked into the instrument panel somewhere. A good rainy day project when the to-do list gets a bit shorter!

You running a turbo engine?

Nice!.......Its quiet, huh?
I meant to do all that when I did mine,but I was too eager to get it all installed and running.I see the SA tank has a remote vent hook up very similar to the FC tank(the little round hole/flange) ahead of the FC pump.Very good for you!I had to do the hole/flange job twice in order to fit up the FC vent,which is seperate from the FC pump assembely. Looks like only the FB has the tank vent integrated with the pickup tubes.

For the gauge,I just used the stock FB sending unit since I wasnt sure if the FC unit was going to hit anything along its throw.I just clipped the FC float/rod off.I did utilize the FC low fuel light,wiring it into the stock FB wiring,since my stock low fuel light sender didnt work.BTW,that light is not just a simple on/off.....I think its controlled by the CPU under the dash,to have the light gradually intensify,as the fuel level begins to clear the sensor in the tank.Takes a good 30-40 miles, from the light coming on dim,to it staying on bright.And itll fluctuate in turns.

For the fuel lines,I utilized the stock FB feed line since its the same size as the stock TII line and the same size as the steel line coming off of the pump unit.my logic is,theres no point going bigger when you have a 5/16" bottle neck right out of the pump.To finish it off,I matched the stock TII system by running another 5/16" FB feed line as a return line.It is prebent and fits right along side the feed line.For a filter,I run the stock FC unit. Its a regular,"rubber hose on barb" type EFI filter so its easy to plumb and change,no wrenches.

http://img.photobucket.com/albums/v2...y/DSC02487.jpg
http://img.photobucket.com/albums/v2...y/DSC02486.jpg

Nice write up, one for the archives if you ask me.

Couldn't agree with you more on that one.

S5 turbo mounted to S4 6-port keg. 2x550, 2x720 injectors, MegaSquirt ECU, Bosch in-tank pump, FMIC, custom 2-1/2" exhaust with twin Magnaflows, TII tranny, GSL-SE rear all in a 1979. I'm running about 8 psi max at the moment. A V-trim hybrid and a second set of 720's are to go in over the winter.

Voted.


One question, How did you rivit the cup to the bottom. Drill from the top?

Nice writeup, thanks! It's just what I plan on doing for my s5 turbo swap, although I'll probably end up welding it in with my mig welder. Like steve keeps saying its factory reliable and quiet is always good, I hate loud fuel pumps or loud anything for that matter, gets real annoying real fast.

archivinated!