Jim Grant's Tech Tips

'95 Ford Mustang GT, Fuel Pressure

Q: I own a ’95 Ford GT with an off-road exhaust, E303 Ford racing cam, minor intake porting, EGR is removed and blocked off at header and intake. The emission pump and a/c are removed, new cap/rotor, and new fuel filter. The car is lacking power, especially on the bottom end and backfires occasionally on hard acceleration. The fuel pressure was good at idle(39 PSI) but dropped to about 30 PSI anywhere above idle. Please tell me what you think could be the problem.

- Garvey

A: This is an easy one. The fuel pressure is going the wrong way. The fuel pressure in your vehicle must climb, that’s right get higher, when the engine speed and load are increased. In your case the pressure is dropping which means the engine is not receiving enough fuel to get up and go. This creates a lean running condition that results in a backfire up through the intake manifold. It may be that the fuel pump needs to be up-dated; there is a restriction in the fuel line or the fuel pressure regulator has a problem. If you find that the fuel pump is the cause for the problem be sure to replace it with a Ford or after market high performance fuel pump. The stock fuel pumps just don’t cut it once and engine has been modified.