MJLJ V3 vehicle installation guide

Vehicle installation

Image courtesy of Steve Randle

Wiring notes and guidelines

• Use shielded cable for the VR Sensor, and the PIP/SAW signal between the MJLJ and EDIS module. Be sure to ground the shield as well. Also note the VR sensor is polarized- you will not get spark from the EDIS module if it is wired backwards.
• Minimize supply voltage variances and ground loop problems: It's strongly recommended you power the EDIS module and MJLJ from the same electrical circuit. Also, ground both at the same point on the chassis.
• The MJLJ should be installed inside the passenger compartment. It's not designed to handle the temperature extremes of the engine bay, and unless you installed it in a weather tight case or potted the whole thing in expoxy, you should keep it away from moisture.
• For MAP based setups ignore the TPS connections.

OEM tach adapter

Many tachometers can accept the 12V signal emitted from the MJLJ module. however, some OEM tachs detect the RPM signal by sensing the high voltage flyback pulse from the ignition coil. In distributor based setups, there is only one ignition coil to detect this pulse from. With a wasted spark system like the Ford EDIS, you will have multiple coils providing this signal. Consequently you may need a way to detect this pulse across multiple coil-packs.

The following circuit allows the flyback pulse to be detected across individual coil packs while still isolating the coils from each other.

OEM tach adapter circuit