Fuel Injector and Resistor Box Basics - Wrenchin'

Determining which fuel injectors you have is simple. All you need is some sort of digital volt-ohm meter (DVOM)-even an analog one will work. Set the tool to read ohms and connect both of the DVOM's probes to the injector's two pins. The injector doesn't need to be installed to do this so just leave it on your workbench.

What do you do when you find out those low impedance injectors you ended up with aren't compatible with your ECU? This isn't really uncommon, by the way, since most aftermarket high-flow injectors are the low impedance type. The easiest fix is to add an injector resistor box. They aren't all that hard to find and can be sourced from many older Hondas or even Mitsubishis, like the Eclipse. A resistor box is nothing more than a simple device that steps down current between the ECU and fuel injectors. It's also not terribly difficult to wire up. For OBD-I vehicles, begin by locating the driver-side harness connectors near the brake master cylinder. Using your multimeter, locate the four wires that go to the injectors. Cut these four wires and connect the injector-side wires to the resistor box's black wires in any order. It's easiest if you score the resistor assembly's opposing plug to make the engine removal easier later on. Connect the resistor box's remaining power wire to all four of the remaining ends of the cut injector signal wires, which will give them their 12V power signal. That's it.

Resistor Boxes...Find Yours

You'll run into two kinds...        read full caption You'll run into two kinds of Honda fuel injectors: peak and hold and saturated. Each provides a different amount of electrical resistance, which means swapping one for the other can spell trouble.	Injector resistor assemblies...        read full caption Injector resistor assemblies like this drop the current between the ECU and injectors by about 8 to 9 ohms when using low impedance peak and hold units. It's important to use a resistor box when pairing low impedance injectors with an ECU meant for saturated ones. The consequences are overheated circuitry.	High impedance Honda injectors...        read full caption High impedance Honda injectors measure within the 12-ohm range and don't need any added resistance-dropping help.
Set your DVOM meter to ohms...        read full caption Set your DVOM meter to ohms and connect the probes to the injector's terminals to see whether you've got peak and hold or saturated injectors.	The resistor assembly wiring...        read full caption The resistor assembly wiring needs to splice in between all four injectors' ECUsignal wires. Cut the injector wires and connect the injector side to the box's black wires and the remaining wires to the box's remaining 12V power wire.