Returnless fuel rail how to make it work

[Guest]

Several months ago I found the heart of the fuel injection system for the GM 8100; fuel pump assembly, and fuel rail with 30 lb/hr injectors. I notices the fuel pressure regulator was attached to the rail in a manner that made me think of the returnless rail on my 3500, and how the regulator had three lines, inlet, fuel rail and return. Since there is only one line coming from the returnless rail on the 3500 I realized that I could cut the 8100s regulator from the fuel rail and connect its 3 lines without ever having to go into my fuel tank for a modification. You can look at the pictures and see what I'm getting at. The line without the plastic safety lock is the outlet to the rail, the other two are inlet and return. The regulator also has a screw on top for pressure adjustment.

I knicked it while cutting or more appropriately butchering it away from the rail with a saws-all but was able to MIG it up as you can see at the bottom of the bowl. I disassembled it first so there was no plastic or rubber on it at the time and everything appeared to be in place afterwards.

[Superdave]

$2.99 for an ignition spark checker is a good deal!


Nice find! i was going to use the 3400 rail with my swap but i might have to look into this as well...

[Joseph Upson]

$2.99 for an ignition spark checker is a good deal!


Nice find! i was going to use the 3400 rail with my swap but i might have to look into this as well...

I was thinking of trying to locate one more fuel rails since I have a second Fiero stored waiting for a work up. Harbor Freight is the Walmart of tool stores, we're so lucky to have one here in town, It's like Christmas everytime I walk in that place.

[prophiseer]

Harbor Freight is the Walmart of tool stores, we're so lucky to have one here in town

Know what you mean here! Between Northern Tool & Equipment and Harbor Freight, if you can't find a decent tool for cheap . . .

[Superdave]

I've got a harbor freight about 2 miles from my house... i love it!

[SappySE107]

Wouldn't it be easier to use the 3400 rail with the adapter piece to change the angle on the FPR?

[DEI37]

Yup...I've got one about three miles from where I work. Haven't bought anything yet, but it's a fun place to go look!

[farmerz24]

any progress on this? id like to use it to eliminate one line going to my rail and reduce engien clutter. i guess there are no aftermarket 3 line fpr's eh?

[SappySE107]

Have you seen the AN-6 fittings for the gen 3 rail? You could run lines however you want.

[farmerz24]

ben, yes i have but that doesn't make it returnless does it? reason being i want to eliminate the return coming back over the engine to the firewall, and also by doing this it lets me run a different "return line" the nos line, without giving it away thats why i want to use the returnless.

[Joseph Upson]

I've been focusing on the wire harness lately and am down to the last plug of four on the 727 ECM so that I can plug it into the engine on the stand and check for spark on all six plugs from the 7x ring.

The picture includes a T-fitting that has an oil pressure sending unit from the Fiero on it. Since it is fuel and oil resistant i'm going to use it and an extra fiero oil pressure gauge or I may use a switch to allow me to alternate between the oil pressure signal and the signal from it to monitor my fuel pressure electronically on the dash gauge already in the car. A Grand National owner confirmed that my idea would work because he has already deployed such a method to monitor his fuel pressure. This way I'll know what my fuel pressure is doing under boost.

If you look closely you can see the return line just beneath the fitting so only one line will go to the rail and it will function as returnless without all of the shananigans inside the gas tank. The sensor will be mounted low away from the engine so in the rare event it leaks fuel will not drop on the engine.

[Joseph Upson]

Mission complete

It works like a charm. Fuel pressure currently sits at 50 psi. The fittings were connected to the existing hoses for the inlet and outlet just after the fuel filter and a single line from the regulator goes to the rail. As for the electric fuel pressure gauge, I purchased a nice complete gauge kit off Ebay instead of siding with creativity.

[mcgavinz26]

What years of the 8100 have this exact part?

[ForcedFirebird]

Bringing back from the dead, but let me get this right. All one needs is the fuel pressure regulator with the three junctions, and plug the return line at the tank?

[Joseph Upson]

Bringing back from the dead, but let me get this right. All one needs is the fuel pressure regulator with the three junctions, and plug the return line at the tank?

No, you plug the return line into the regulator, 3 lines remember, one to the regulator, one to the rail and one back to the tank. Pretty much like an oil filter relocator only in this case you are relocating the regulator. Look at the third picture. The hardest part is cutting the regulator free of the rail without damaging it like I did my first one. The input and output lines are quick diconnect barbed hose fittings.

It should be on the first year of the port FI 8100 V8 starting in the early 00 if not a little earlier. You'll have to look for the intake because that's how they are usually sold in which case you'll probably get the injectors which are 30 lb/hr and are the proper size for the 3500 and 3900 fuel rail.