EFI Fuel Supply Design

[BillGrissom]

Finished my EFI fuel system and thought I'd share my approach since I spent way too much time. May ease the path for others. Not asking any questions, but would appreciate useful comments for me and others.

My plan is to first supply a carb, then TBI, and eventually MPI, with minimal change to the fuel system. That way, if the TBI fails on the highway, I can switch back to the carb to get home. Of course, can't backup once I go MPI since a different manifold. I start with a carb because I have one I know works and don't want to wipe my new cam when I firt start the engine, plus want to document the mileage difference between the 3 fuel systems.

Details to the photos:
Sender is 3/8" supply and 1/4" return (ebay ~$45 new).
Ran 3/8" steel line and "fuel injection" type rubber hose. Used the factory 5/16" line for return. I tried to minimize rubber hose and used barbed fittings w/ "fuel injection" type clamps where I had to use it. I slightly flared bare steel line to better secure the hose.

I used SAE flare fittings on the steel tube. Compression fittings are not recommended since theoretically the tube could pull out of the nut and cause a massive leak. Two flares leaked slightly, but I fixed by inserting a green O-ring in them. A thin copper "soft seat" or "Voishon washer" is the suggested fix, but didn't have any.

The fuel pump is a Walbro 190 LPH (GSL391?). Several fittings are available for the 10mm x 1 threaded ends. I used the 3/8" barbed hose fittings, which come in the $10 installation kit. I drilled and tapped 2 holes in the passenger side inner fender to mount. The pre-filter is a generic 3/8" type. I covered the hose w/ silicone-fiberglass heat shield where it runs past the exhaust header.

Following the pump is a Microguard 33737 filter/reg ($20 at O'Reilly's). It is used on Corvettes and relieves at 58 psi. Inlet fitting is NAPA 730-4927 (3/8"), return fitting is NAPA 730-4926 (5/16"). For the outlet, I bent a 3/8" tube from an early Magnum SB fuel supply (regulator rail).

At the pressure gage, I switched to 5/16" fitted hose from a later Magnum SB (return-less rail). All three of my fueling systems will attach to this hose via a male 5/16" quick-connect tube ("Bundy" fitting). For the carb, I used a piece of tube from the later Magnum. At the carb, I made a tube w/ dbl-flare to SAE flare.

For the carb, I need to run ~10 psi at the fuel pump outlet. I have an old Pro-Fuel type pressure-reducing regulator to supply the carb at an even lower pressure (adjustable). I first tried a home-made 10 psi bypass reg made by adding a hose barb to a Norgen 30 psi air relief valve (shown) and swapping in a weaker spring. It tested 10 psi w/ air but ran 22 psi on the fuel pump. It held a perfect 10 psi w/ pump off. When replaced with just a hose barb, the system ran 9 psi. Thus, most of the extra drop was due to the return plumbing, most likely the 1/4" restriction at the sender. Only 3 psi was "proportional offset" in the reg. This determined I don't need the bypass reg, and can just use the return drop for the carb. However, when I switch to TBI might be a problem since the Holley Projection specs <4 psi drop in the return line.

Pre-emptive answers
1. The fuel pump is pretty quiet. Can barely hear it in the cabin with the engine off.
2. I know people recommend installing the fuel pump close to the tank, but didn't see a good place, wanted a clean protected place and where I can access it on the highway if it fails, and I have run one for decades on the inner fender in my Newport with a 5/16" supply line and no problems.

Finally, since someone recently asked "what EFI pumps are there?", I show 2 other external types I know of besides the Walbro. First is the "1990's Ford Truck" type I run on my Newport. Similar ones are sold under many brands (MSI, Holley, ...). I have only seen outlet fittings for 5/16" hose. The thread looks like 1/4-20 but don't quote me. The inlets fittings I show are 1/2" and larger, but I have a 5/16" inlet on my Newport. The other pump is a Bosch used on Mercedes, Audi, etc. It has a 12mm - 1mm threaded outlet. The installed fitting is a banjo-type w/ check valve. The inlet is ~1/2". I bought it cheap but will re-sell since too hard to adapt.

 

[omahamoparguy]

the thing I dont like too much is the steel filter that close to the exhaust, maybe it is just the way the pic makes it look like it is close to the exhaust. I guess with all the psi and the bypass it will be ok and not cause fuel percolation issues. The new fuels (if you can call them that) dont like heat, but since this is fuel injection..../I am not too fond of those types of regulators (shown before the carb) but I understand the idea of getting the psi down for carb usage so I think that will work. Dont you need a grommet for the line going through the frame section there? (by the jackstand). I'd clamp that to make sure it wont rub or have a possibility of moving. Other wise, I like it!
By the way, do you remember the article called "the frugal fuelie" a way back in mopar action magazine? Seems like a similar build ideas. (Article is somewhat hard to find)

 

[inkjunkie]

I understand your problem with mounting the fuel pump in the rear of the vehicle. Problem is efi pumps are pushers, not suckers. They are good at creating high pressure, but not at creating the vac. needed to pull fuel thru the line. If the pump is going to stay in the engine compartment you might want to look into an accumulator, similar to the one here http://www.bcbroncos.com/store/index.php?cPath=131_108 so you have a constant supply of fuel. One thing efi does not like is to not have constant fuel and with your set up, unless the tank is sumped, you are bound to suck air into the system when the tank is low. This accumulator will require a low pressure pump in the rear of the vehicle to supply the fuel to it. This is how Ford did there efi systems when they first came out, at least on the Rangers. If you go this route, there will be more equipment to deal with as well as 2 pumps. But it will give the injectors a steady supply of fuel. I swapped an EFI set up into a Ford Ranger I had and used an external pump mounted as close to the pickup in the tank as I could get it. We put 200k on it and it still had the same pump in it, so I would not worry so much about the pump burning up. No nice way to say it, your idea is probably not going to work real well when you step up to injection....might want to contact fastmanefi, I think that is his name here. Rich operates http://www.fastmanefi.com/ and would be a great guy to talk to about this.....

 

[player1up]

I'll be running a similar setup for the blow through turbo.
I've got a walbro gsl392, Mallory 4309 bypass regulator, 5/16 supply 3/8 return. The great thing about the setup is that if I step up to TBI or EFI, All I have to do is change the spring in the regulator and dial it up to the right pressure.
I've got everything installed except for the new pump. I'm just hoping that the regulator and return are able to bleed off the volume that the pump can supply...

 

[DJVCUDA]

I just went EFI - and had a similar dilemma - the dual fuel setup can be done with what I have - since I have the stock sending unit blocked off, but it could be used if needed.

I went with a rock valley tank, they sell a sump of sorts that you can weld in or they have complete units.

The unit has a spiral sump that holds fuel at the pump ( internal )

I've had under 1/8th of a tank, and still cannot get it to suck air - the system works and works well.

I agree with INK - you will suck air, and the pump will fail, they are pushers, not puller.


my setup :

 

[BillGrissom]

I definitely agree with the concerns with sloshing fuel and sucking air into the pump. I have run a similar setup in my Newport since 1996. I initially tried a little pusher pump near the tank, but caused more problems than not. I tried many combinations. A little rattle type starved the EFI pump. A 7 psi Carter round one worked, but was a beast. A Holley radial-vane type (blue) worked fine. Indeed, I upp'ed the relief spring to 20 psi and ran that alone to supply the TBI for several years. When the blue pump started leaking, I decided to try just the Holley gear-rotor pump in the engine bay for easier access, which has worked fine ~10 years. Gas pours out of the 5/16" supply tube, so I didn't see how that could starve the pump.

You know when the pump sucks air because it screams. That happened a few times in the Newport when down to ~2 gallons and braked hard. A sump in the tank would be nice, but welding one in is scary. I try to keep at least 3 gallons. A good sock on the inlet helps. I saw the Rock Valley tank that DJVCuda has. Maybe when my 2nd son finishes med school I won't be "The Cheap Mopar Bastard" that ScareBird relates. BTW, I killed my first gear-rotor pump because I had the bright idea of sticking a chem lab type cotton filter in the supply tube to protect it. It doesn't like any supply restriction.

In my Dart, the steel pre-filter is against the inner fender and above the torsion bar, so doesn't sit above the exhaust tube and ~5" away. Should be good air flow, but perhaps prudent to wrap with broiler foil. Where I covered the fuel hose it passes ~1" from the exhaust flange, but is below the flange.

The factory fuel line also runs thru a bare hole in the torsion bar frame. I filed the hole to remove burrs, but sounds smart to jam something like teflon sheet around the tube. Based on my Newport experience, a 5/16" supply should work fine, unless maybe you run the 255 LPH pump. I went 3/8" to match the Corvette reg fittings.

The racing type bypass regs are very expensive (>$100) and fairly large. However, I see after-market ones ~$50 on ebay, intended to replace factory rail regs. They are intended for MPI pressures and don't know if you can change the spring. For an MPI reg, you can't beat the price of the Corvetter filter/reg. The Norgen relief I used is very small and costs $3, but requires some fab. I may revisit why I get 9 psi return drop, fix that, and use the Norgen reg, but bigger fish to fry now.