AFRO IROC Z

A couple of my friends have '99 and up mudstangs. Their fuel delivery system doesn't use a return line. To me it seems like it would be very taxing on the fuel pump, because it works by using a sensor in the fuel rail that tells the computer how much fuel to add to keep the pressure up, but that means the fuel pump gets pulsed, so it is on and off repeatedly Right?? Is this system better than the ones with return lines? Are there any gms that use this type of fuel delivery system?? How do these systems meet the demand requirments of a power adder like a blower or a turbo?? Any info would be appreciated. Thanks.

El Guapo

There are theoretically two ways of doing this.

1) Constant speed pump w/ some sort of FPR and return system
2) Pulsing, on till full, off. On till full, off.

As you can imagine, the constant speed (Volume) pump would be very much preferable. It keeps from starting and stopping. On the Ford, the pump itself may have a relief solenoid or spring or something to allow the fuel to immediately return to the tank. Or they may have an FPR under the car. But I'd place money on that they have a constant pump w/ some form of FPR and fuel return.

Lets say the line is full at say 40PSI and the pump is off. As soon as the owner hits the gas, the pressure will drop, since the pump isnt trying to keep more in. Course, at this time the pump comes on, but the pressure is down to say 30PSI. Now the pump comes on, but they need to spin up. There will be some lag. So by the time the pump can come up w/ 40PSI, the line had dropped to 20PSI. This car would have consistency problems.

I will look around and see what I can find, but the pulsing doesnt sound very smart.

Clayton

Kenn

A returnless fuel system is an effort to reduce evaporative emmissions by not running the fuel through fuel rails where it picks up heat and creates more fuel vapor in the tank

I second that ford used a constant volume pump regulated at the tank (not sure if its vacuum or computer regulated) but there are other systems that vary the voltage to the pump through feedback from a fuel pressure sensor to maintain a constant fuel pressure as opposed to completely stopping the pump

but either way theres not an easy way to tune by adjusting the fuel pressure that I can think of - but I'm not a ford person

GMTech

These guys are correct. Returnless fuel systems have a regulator in the tank. The theory is to not have fuel go to the engine to heat up, then get pumped back into the fuel tank because it wasn't needed, then evaportate in the tank causing an HC buildup.

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