| This is an update to a posting that I made last July (wow a year already!!!). That auto-FAQ can be found here >> La-Z-Link Over the winter months I pulled the upper plenum for maintenance including injector replacement and the installation of new injector connectors. Due to time pressures in getting the project completed, I felt it was easier to slightly modify the circuit installed last year -- adding a relay for turning off +12 volts to the injectors when the car wasn't running. I decided not to mess around with the wiring bundle near the ECU (per this auto-FAQ >>La-Z-Link) mainly because my winter servicing dragged into June, this mod was mostly ready to go from last year and it was a fast way to finish things up! Under different circumstances -- probably would've tried the ECU bundle method instead. Here's the modified circuit - additions to the circuit from last year are highlighted in yellow:
Circuit Notes: Circuit operation -- ignition key activates A/C power circuit which in-turn activates the relay. Relay contacts then close supplying +12 volts from the injector harness to each of the injector connectors. The 4 amp fuse is used to protect the switched +12v line from relay or wiring short circuits. When I spliced in my new injector connections to the harness -- I made sure to run the common +12v connections to a line which returned back to the fuse box (relay). A second line was added (from last summer's work) and spliced into one of the +12v always ON harness (source power) wires and then routed back to the fuse box (relay). Made a design decision to add a relay and switch the injector harness +12v supply rather than using another +12v supply source from the fuse box. Main concern was in adding "hum/noise" onto a power line which in turn could create issues with the head unit or amps. Doing it this way meant running another line from the fuse box over to the injector harness. That is, two lines are now running from the fuse box to the mid-plenum wiring area. These lines are easy to route - just need a few wire ties to bundle them neatly to the engine harness. The injectors draw at best 1.5 amps of current - so the relay's contact (current) rating isn't critical. A 10 amp or 20 amp relay is even overkill - but the part is readily available in many places (and cheap).
Parts needed for the additions are:
- 4 insulated female spade type crimp connectors (for relay) - 1 crimp ring terminal (for fuse box screw - ground) - 6ft of 16 or 18 guage wire (add'l line going to injector harness) - Misc: Wire ties and shrink fit insulation - 1 automotive relay (Radio Shack, car store, etc) - pretty much any rating: 10, 15, 20 amps - doesn't matter. The relay needs to be modified a bit to fit inside of the fuse box:
 Here's how the relay and other parts were positioned inside of the fuse box (see earlier FAQ for more pictures) Note: Even made a short piece of line with two male connectors - very easy to bypass the relay and restore the car's wiring back to its original configuration (i.e., pull the two RED crimp connectors from the relay and jumper them). Stored the jumper in an empty fuse box location.
 The relay's coil was grounded using the fuse box lower hold-down screw
 This circuit has been in the car for over a month with no issues. I can't say for sure if it will improve the life of my injectors but figured it can't hurt to try? DISCLAIMERS… READ AND FOLLOW ALL SAFETY PROCEDURES RECOMMENDED IN THE NISSAN SERVICE MANUAL FOR WORK ON THE 300ZX Z32 ENGINE. MAKE SURE THE CAR’S ENGINE IS COLD TO AVOID BURNS AND DISCONNECT THE BATTERY BEFORE STARTING ANY WORK. ALWAYS TAKE PROPER SAFETY PRECAUTIONS AND USE COMMON SENSE WHEN WORKING ON THE ENGINE AND ELECTRICAL SYSTEM. YOU ARE RESPONSIBLE FOR YOUR OWN SAFETY WHEN WORKING ON YOUR CAR. THIS WRITE-UP IS AN EXAMPLE OF ONE WAY TO PERFORM THIS MAINTENANCE, IT MAY NOT BE THE SAFEST OR BEST WAY TO DO IT. YOU ARE RESPONSIBLE FOR DETERMINING HOW THESE REPAIRS SHOULD BE EXECUTED IN A SAFE AND CAUTIOUS MANNER -- AUTHOR IS NOT RESPONSIBLE FOR ANY HARM TO YOU, YOUR CAR, FUTURE GENERATIONS, YOUR PROPERTY OR TO OTHERS WHILE OR AFTER PEFORMING THIS OR ANY OTHER AUTOMOBILE SERVICING... .
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Update: Injector Switched Power Line Using Fuse Box - 
