ZEX Nitrous Kit Installation for 86-93 Mustangs 5.0 Part Two

ZEX Nitrous Kit Installation

Now it’s time to wire up the 3 wires coming from the NMU which are Red, Black & White. Connect the black wire to a good ground anywhere in the area of the NMU. You can use one of the screws that is holding the NMU in place. Connect the White wire to the Green wire on your TPS using the supplied T Taps. Use a piece of red wire the same gauge as whats coming from the NMU and route in from under the dash, thru the firewall using any routing you like and make sure you have plenty of wire and connect it to the Red wire from the NMU using a butt connector. Take the other end of the Red wire and connect it to the arming switch which has the supplied connector already attached. Take the other wire from the arming switch which has a fuse assembly (15amp fuse already installed) and connect it to a 12 volt accessory wire using the supplied T Tap. (I tapped off a pre existing wire connected to a 20amp fuse). Now just find a suitable spot to mount the switch along with its red cover shield. It requires a ½” hole.

THAT’S IT. YOU’RE DONE! The only thing left to do is Program the activation switch and check the vaccum & pressure lines.

“Programming the activation switch”

Turn the cars ignition ON but don’t start it. Turn the arming switch to ON, then go to the NMU and located the “Push Button”. Depress it, and then release it. Observe the NMU’s operation light. At this point it should be RED. The RED light informs you that the NMU’s activation switch is in the “LEARN” Mode. Go back to the inside of the car and depress the gas pedal to the floor for 10 seconds. Release the pedal and go back to the NMU and observe the operation light. At this point the light should be flashing continuously from RED to GREEN to OFF. This is the NMU’s way of telling you that it has successfully learned the voltage curve of your motor’s TPS. Go back inside your car and turn OFF the arming switch, then turn it back ON. Go back to the NMU and observe the operation light. It should be solid GREEN. This informs you that the system is armed and ready to activate at WOT. Return back to the driver’s seat and depress and release the gas pedal several times. You should now be able to hear the solenoid “click” each time you reach WOT. Your activation switch is fully programmed and ready for use. NOTE: Should you ever transfer the Nitrous system to another car, perform this same procedure on the new vehicle to “relearn” the NMU’s activation switch.

To ensure that the system is ready to be used, a final vaccum and pressure check of the systems hoses and lines must be done. With the motor running, check your “intake” and “regulator” hoses for any vaccum leaks. Generally a vacuum leak will cause the motor to run rough. Assuming the vaccum lines check out ok, open the Nitrous bottle valve and listen carefully to your motor as the valve is opened. You should NOT hear a difference in the idle speed or motor sound. If you DO, then contact the ZEX tech Line at 1-888-817-1008. If there is NO change in idle speed or motor sound, shut the motor off and inspect the Nitrous pressure lines and fittings for leaks. Leaks in the Nitrous supply line will be obvious because they will be covered with frost.

Always use Premium fuel of at least 92 Octane (R/M Method) and that your ignition timing is set correctly.

On the 5.0 Litre Mustang:

  • 75HP= #40 N20 jet/#43 fuel jet with 0 retard (10 degrees)
  • 100HP= #46 N20 jet/ #40 fuel jet with -2 degrees retard
  • 125HP= #52 N20 jet/#38 Fuel Jet with a -4 degree retard

Use 1-2 step colder plugs and make sure their gapped at .35 or if you have a CD box (such as MSD) you can open the gap to .40-.45.

Additional Parts required before installing:

  • 1 length of 3/16” hose, 3 ½’ long
  • 1 length of 3/16 hose, 4 ½’ long
  • 1 roll of red wire (14gauge)

Back to Zex Install Part One

You may also be interested in . . .

  • This is an Installation guide on how I did mine for my ZEX N20 Kit, the Bottle warmer and a electric fan on a 5.0 Litre Mustang.

  • The ZEX kit for 5.0’s is a dry shot system which uses a spray nozzle that’s tapped into the air intake hose for delivery.


    • 14 GAUGE WIRE
  • A fuel cutoff switch can be a security device both in the sense of saftety and a theft deterant. When done properly no one will even know it exists except you.

  • If you haven't already read how to do it a million times in all of the Mustang magazines then this is your chance. Here's how to check and adjust your TPS voltage. You may be asking, "What is a TPS"? Simply put its a Throttle Position Sensor. The TPS is a sensor that tells the ECM (computer) how much gas you are giving it, which in turn lets the computer decide how much fuel and spark to give you.

    • Unplug the negative battery terminal THIS IS VERY IMPORTANT.
    • Disconnect your starter from your bellhousing.

    • 15 ft. of 1 gauge wire,(Lugged on both ends).
    • 15ft. of 4 gauge wire, (Lugged on both ends).