[namba209]

Building the Fuel System

As stated way back in Phase I, the V-6 SFI requires a higher pressure/volume fuel pump than the OEM Opel pump can put out, so a search was done in the AC Delco fuel pump book and a suitable external replacement fuel pump was found, along with a high pressure fuel filter. The plan was to put a filter on each side of the pump and mount it back by the fuel tank, but a couple of threads on this site discussing the EFI fuel delivery problems encountered in the GT made that setup appear to be unsatisfactory. Basically the problem encountered was, due to the shape of the GT fuel tank, under spirited driving conditions with about ¼ tank of fuel left, the fuel could slosh away from the fuel pick up in the tank and the fuel pump would pump air into the fuel line. Not a good thing, especially if the engine is running at a fairly high RPM and air is injected in the combustion chamber. The general consensus was to have a separate, remote or surge tank that would have only fuel in it so the high pressure pump would not deliver air to the fuel rail. After some considerable thought, I drew up a fuel system that is similar in design to the fuel systems on my model racing boats, that does the exact same thing we were looking for on the EFI systems, that is, to eliminate any air going to the carb on my racing engines. Of course I had to add a few lines to take care of, the return or pressure bypass fuel from the pump and fuel rail, along with a vent line coming from the tank to the charcoal canister. As luck would have it, my neighbor replaced his water filtration system some time ago and gave me the filter housing from his old system. It was a polished stainless cylinder that was in two pieces held together with a “Marmon” clamp and a very large fat “O-ring” for sealing the two halves, and had three fittings welded on the end of one half. The fittings were 1/8” pipe thread, a fairly common size so fittings were not that hard to come by, with the center fitting going through the housing inside with external ¼” pipe threads on it. It was a simple matter to see that all I had to do was put a standpipe on the inside fitting so the bottom of the container was always under fuel and put a hose fitting on the external fittings, one for fuel in, one for fuel out to the pump and the third would be from the standpipe for overflow back to the tank. All I needed to do now was get a low pressure, high volume pump to feed the surge tank and an inline filter in front of the pump. After looking real close at what I had and what I needed, I redrew my fuel schematic to comply with what was needed and what I had in hand.

About this time, my friendly welder came by with two pieces of 10 foot ¼” stainless steel tubing. He knew I was thinking about using it for the fuel system, and run across it at one of his welding jobs, and it was going to be trashed. I asked him if there were any larger sizes there and he said he thought there was and he would check. A couple of days later, he came by with another two pieces of 10 foot ½” stainless tubing.

I did a search on the web for electric fuel pumps and came up with a Facet fuel pump from JC Whitney, for a reasonable price and ordered it on line. When I got the pump, I rigged up the surge tank and the two pumps and ran fuel from a gas can to the low pressure pump, to the surge tank, from the surge tank to the high pressure pump, back into the gas can. The idea was to see if the low pressure pump could keep the tank full, feeding the high pressure pump dumping fuel out of the surge tank with no restriction. It worked beautifully, except the Facet pump was extremely loud. I had another fuel pump laying around I was going to put in my van, so I put it in the system to see if it would work as well as the Facet pump but run quieter. It was more than up to the task and a lot quieter, so I laid the Facet aside and put in the older pump.

Now it was time to figure out where all the bits and pieces were going to go in the car. It would be nice to have an idea because I was still working on the wiring harness at this time and running wires after building the harness was not a good plan. It was already predetermined the low pressure pump, hereafter renamed as the boost pump (USAF terminology), would be in the rear of the car, close to the tank. So a 12 gage wire was included in the harness going to the rear of the car in the tail light wire bundle. I used the original vent line hole in the floor at the rear of the car to route that wire to the boost pump. I also drilled two holes behind the duckbill vent for the return and vent lines going to the tank. Next was to figure out where the filter and pump would go. I had seen other fuel pumps mounted forward of the axle, but because I was running dual exhaust, I needed the fuel components away from the proposed route of the exhaust. I mounted the filter in the corner just behind and inside the rear of the wheel well and mounted the boost pump on the inside of the frame rail behind the axle. That should give me ample clearance for the exhaust to run under and inside the fuel lines where it goes over the axle housing. I hope.

My original idea for the front fuel system was to mount it on the back of the structural member in front of the battery. But that went by the wayside because the battery has to be removed from under the car, through an access panel because of the air conditioning condenser in front of the radiator will not allow the battery to be removed between the radiator support and the front sheet metal , so the components were required to be put in front of the structural member. There’s just no other place for them to fit.

Originally I had a tube welded into the filler neck and bent down 90 degrees so the end of the tube was accessible below the filler neck tube to put a fuel hose on it, to eliminate the sound of fuel running back into the tank. During assembly the tube broke off at the weld. Here’s a hint, don’t use an old ¼” brake line for a fuel return line, they break when they get too hot. So another call was made to my friendly welder and he put a new steel hose fitting in the filler neck tube. I’ll have to live with the sound of fuel returning back into the tank. That may not be a bad thing, at least I’ll know if the pumps are working.

After all the major pieces were installed in the car, it was time to run the lines from the tank forward and back. The ¼” lines were fairly easy to bend by hand, but the ½” line was a bear, and I didn’t have a large enough tube bender to accommodate that large size. My first couple of bends put small crimps in the tube, but not so severe that I won’t have a good fuel flow from the boost pump to the surge tank. I purchased a whole bunch of rubber cushion clamps and Teflon cushion clamps for the fuel, vent and brake lines to hold them in place. Along the frame there are numerous straps that the original lines were wrapped and held in place with. I straightened out the straps and drilled a hole in each end of the straps to fasten the clamps to, two on each leg. It turned out really neat and kept them looking almost professionally made along the frame, up into the engine compartment and up through the holes in the radiator support sheet metal to the front of the car.

I decided to run just one 10 foot section up into the engine compartment and attach 3/8” high pressure fuel injector hose from there to the surge tank, to the pump, filter and fuel rail. The reasoning was, I almost screwed up bending the tube making small radius bends and didn’t want to take the chance making some 90 degree bends.

All that’s left to do now on the fuel system, is get some gas in the fuel tank, put the engine back in the car and pressure check the whole mess and look for leaks. Another Phase completed.