What "Pros" and "Cons" for Double and Single Fuel line Systems.

[skullandbones]

I built my roadster by the book when it came to the fuel system on the EFI. My donor system was 92 GT so I used the tank, pump, fuel rails and regulator, the hard lines from the kit, and EFI rated rubber tubing and double clamps. I flared the ends of the hard lines to act as a preventer from lines popping off. I did switch to a DIY charcoal canister close to the tank. I have my focus on this system now as it served me well for the first 3K miles but it does not meet the needs of the engine for performance. While contemplating the upgrades, it occurred to me that keeping the 2 fuel line system or switching to a more modern setup should be considered, as well. I have my eye on a fuel rail kit that will accommodate either way I go with the upgrade. To tell you the truth, I don't like the vacuum controlled regulator (don't understand the concept very well). So simplifying the system would make me happier as it would follow the overall concept I have tried to follow (KISS). As of this writing all but one or two things on the roadster are function driven with a goal in mind and not much focus on bling. The fuel supply system could be an issue or if the pros out weigh the cons, it could be left as is (with upgrades of the pump and fuel rails). So I was looking for some sage advice and your personal experiences with this system to help me make an informed decision about moving forward. I definitely want to upgrade to make the system optimal for the use of the car (spirited driving with some track this season).

Thank you,

WEK.

[OCCPete]

Are you saying you want to change to a returnless system? That would require changing the entire EFI system as in a returnless system the ECU regulates fuel delivery by controlling the speed of the fuel pump or by changing the duration of the injectors based on load.

[skullandbones]

Pete: OK. I guess that makes sense since I remember when I was hooking up the EFI harness that one wire out of the computer did go directly to the fuel pump with a breaker in the black box (Summit EFI harness). I don't have to change anything with the fuel supply lines then. I'll keep the return type system. I'm till wondering if my stock fuel regulator is working OK. I guess I will have to do the pressure check on the fuel rails while running down the road. Jeff K. suggested taping it to the wind screen. I guess that will be the way to do it.

Thank you,

WEK.

[CraigS]

The vac pressure works quite simply. Sitting in the garage you can test it's function. Connect your pressure gauge, note the reading and pull the vac hose off the regulator. Cap the end of the hose w/ you finger. You should see a bump in pressure of maybe 5-10 lbs. I don't know the specific number. When you have little load on the engine you have max vac so you have the lowest pressure. As you put your right foot down, the vac drops off, the pressure increases, and you get a richer mixture. This happens automatically w/ no input from the ecu. It's really a neat idea to get an instant reaction to the movement of the gas pedal. I suspect they did it this way because back in the day the ecu was like all computers of that time-pretty slow compared to current technology.

[Jeff Kleiner]

I agree completely with Craig and will add my usual "why reinvent the wheel?" With 24# injectors a healthy stock pump working in conjunction with a clean in-tank sock and inline filter should not have a problem keeping up. You are correct Bill, at times I have suggested connecting a pressure gauge to the rail with enough hose so that you can run it out the back of the hood and tape it to the windshield so that it is visible for rolling diagnostics. If you're starving for fuel checking it in the garage with RPMs or by cracking the throttle won't show it---you've got to get the engine under a load and the only way to do that is rolling 2nd &/or 3rd gear pulls to the stumble or redline. If you don't see a corresponding drop in fuel pressure when you encounter the hesitation or stumble it isn't a fuel pressure problem. Should you decide to upgrade the pump I've had good service on a multiple cars with Walbro GCA719-2 pumps. These are 255 LPH but this is one place where sizing larger than your actual need won't hurt you any and you'll be set with plenty of capacity for possible future requirements with very little increase in cost (about $20 more than a 140 or 190LPH pump).

Good luck!

Jeff

[skullandbones]

Had a discussion with a Dyno guy recently regarding my issues. He made two suggestions for upgrades before I even make a visit to his shop. One I was planning anyway. That was the new higher capacity fuel pump. He, too, suggested the Walbro 255 hi pressure pump. I ordered it 2 days ago. Should be here today. Also, he mentioned the MAF and had specific advice. I'm not sure about changing that out right away. I would like to try the new pump after install and checking for any debris, water, other fuel issues in the fuel lines or tank. The other suggestion he had was to go with the C&L MAF housing with a properly calibrated tube and my original electronics from the 92GT to match the ECU. He said it works better with the Ford specific software he uses (tunes lots of Mustangs and better in general). I'm still deciding on that suggestion. This is a evolving thing with my roadster since I put it together as a donor build. I have saved some money (save now but spend later on upgrades) by doing so but it means changing things as you progress thru the process to get to a real performance level that is your goal. At some point, I will have to scratch my head and think hard to remember where the remaining donor parts reside.

Thanks, WEK.