How to diagnose a bad injector – (KL Engine only)

[yel-low]

As with every other guide written, please use caution when performing the following. I will not be held accountable for any damage to yourself or your vehicle.

Materials Needed:
A Good Multimeter
A few simple hand tools to gain access to the connectors.



With that being said, here is where the Front (left hand) and Rear (right hand) fuel injector bank connectors are located. I had to disconnect the battery and remove the intake hose to gain some clearance for my meter’s probes. That is easy enough that I won’t go into the details on how to do that. The front bank will have a rectangular connector. The rear will have a square connector.

[yel-low]

This is another shot with the connectors from the rear

[yel-low]

This is looking into front connector’s (rectangular) harness plug. What you need to notice in this picture are the individual female pin receptacles. From this point on we will only discuss the male pins on the rail itself since that is the part that contains each injectors coil connection.

[yel-low]

This is a shot of the end we need to test. Notice the male pins in both connector housings.

[yel-low]

This is where we will start testing. We will start with the rear (RH) injector rail connector. Notice the orientation of the alignment tabs. Injectors 1, 5 , and 3 are connected here. The individual pins are labeled (A, B, C, D)

The purpose of labeling these pins is because we will be using our multi-meter set on resistance test (ohms) to measure the resistance of each internal coil on the injectors.
Pin A is common through out all the injectors on this rail. We will keep one of our meter’s leads on this pin (A) during the entire test. The remaining lead will probe the remaining pins. As we probe we will come up with a sort of logic table.
Pin A -> Pin B = Injector 1
Pin A -> Pin C = Injector 5
Pin A -> Pin D = Injector 3
The resistance between all pins should be ~13-14 Ohms. A slight deviation is ok but if you come up with a short or no resistance at all then you know the associated injector is dead.

[yel-low]

The procedure for the front (LH) injector rail is the same as the rear. Injectors 2, 4, and 6 are on this rail.
Here is the pin-out for this rail.


For this side, pin D is common to all injectors.
Therefore:
Pin D -> Pin C = Injector 2
Pin D -> Pin B = Injector 4
Pin D -> Pin A = Injector 6
All resistance between pins should read ~13-14 Ohm as above.


There you go, a quick and dirty (or not so dirty) way of testing your injectors. No need to pull the manifold off or touch any fluids. Hope this helps someone.

[milly00]

Nice write-up Randy. Thanks! I'm sure I'll do this sometime.

[jmohr]

yel-low. Thank you for this great posting, it made it easy for me to fine my bad injector.

[Saint_]

Does this mean the injectors are totally ok, or can they still leak even if the resistances are within range?

[mazda-fla]

All this test proves is whether or not the coil winding inside the injector is broken (basically open circuit). If it ohms as open circuit, the coil winding inside the injector is completely broken and detached. If it ohms out of range (but not open circuit), it means the wire is broken, but kind of loose and hanging there and kind of touching. Open circuit will be a permenent misfire all the time. Ohm out of range will mean that you will get an intermitent misfire. Usually, you get a misfire when the car is cold, but as it warms up and gets hot the coil winding (basically a coiled wire) heats up and expands. Then the broken parts of the coiled wire inside the injector touch each other, or come closer together as they expand so the energy can jump between the broken parts (kind of like the way energy jumps the gap of a spark plug). This condition usually gets progressively worse over a few weeks/months, then ultimately breaks completely and you get open circuit.

As far as testing for leaks, this test won't prove that.

To determine if the injectors leak, you would have to remove the couple of nuts/bolts holding the fuel rail to the intake manifold, leave everything else connected (including fuel line). Then lift up the fuel rail 2-3 inches so you can bend your head down and look under there. Then jump the fuel pump at the diagnostic connector port. Let the pump run for 5 minutes and fully pressurize. Then sit there and watch for a few minutes to see if any of them drip. If any of them they are leaking, you would see a drip about one drop of gasoline every 3 seconds or so. If it drips one drop every few minutes, no problem. But one drop every few seconds, then that would be a leaky injector.