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Fuel Injector Upgrade

Time: Less than 1 hour




Upgrading your fuel injectors is a fairly simple task. Start by removing the intake tube from the throttle body to the Mass Air Sensor. It should be held together by either a clamp or screw bracket. Remove the wiring harnesses from the Throttle Position Sensor (TPS) and Exhaust Gas Relief (EGR) valve. Also take off the vacuum hoses from the EGR and vacuum source behind the EGR.

Using a socket wrench, unbolt the intake bolts. In our case, we used a 1994 Mustang Cobra so there were 6 bolts. Reach behind the intake and unplug the Positive Crankcase Valve (PCV) from the lower intake. There should be at least one small vacuum line coming from the upper intake, so unplug it as well. Remove the upper intake and set it aside.

Your fuel rails are held to the lower intake by 4 bolts, 2 on each side. Remove them and lift off the fuel rail. Remove each of the eight fuel injectors and set them aside. Fuel will leak out, so clean up the excess fuel with a clean rag. Your new fuel injectors should be lubed. Using oil or Petroleum Jelly will crack the O-ring seals over time, so we used a water based KY Jelly. Lightly rub each injector's seal with the lubricant.

Gently place each injector into the fuel rail by twisting it back and forth until it snaps it. After all eight have been inserted, lower the fuel rail into position and lightly push each injector into its hole. They should pop into place. Bolt the fuel rail back into place. A new plenum gasket is needed. Place it on the lower intake. Be careful when aligning the gasket, as it needs to be aligned perfectly. Gently place the intake plenum onto the lower intake, without moving the plenum gasket, and bolt it down as well. Reconnect all vacuum lines and electronics.

Remove the negative battery cable and open your driver's side door to drain the energy out of the system's reserves. This will reset the EEC and allow it to re-learn your new changes. After 10 minutes reconnect the negative cable to the battery.

Your Mass Air Flow sensor will also need to be replaced with one that is properly calibrated for your injectors. We installed a Pro-M 80mm in the fender-well. If you have an Fuel Management Unit (FMU) you will need to calibrate that as well.

- Scott Halihan (Rebel79)

* Please use extreme caution whenever you are working with fuel.  It is explosive.