Fuel injector not firing

[Hooter]

One of cyclinders on my 240sx has quit functioning. I have eliminated the ignition system as the issue and am pretty sure the fuel injector is not functioning. If I unplug the 3rd injector it does not change the way my car is running (the others prevent it from starting). Im looking for some advice on how to issolate the issue within my fuel injection system, for example, how to determine if its electrical or physical, and if someone could provide some good take apart info about the electrical portion of the injector thatd be much appreciated (I have the manual, but its no help).

[navysnail]

get a noid light to be sure (GM light works)

[Hooter]

Great, thats exactly what I was looking for. Looking into this though, there's 3 GM types. Which one should I go with?

GM TBI, GM PFI or GM SCPI?

[NISTECH]

I think its PFI small 2 pin one. You should also use an ohm meter to test the injector itself. The noid light is to check to be sure the ecm is pulsing the injector. Take an ohms reading on the injector and the one next to it. the reading should be around 14 ohms. If the one thats not firing is open [no indication] it is shot.

[s13sr20chris]

long screwdriverput your ear on the handle and stick the tip on the injector. compare it to the others. if that one is a lot quieter then its not firing at all.

[Hooter]

Haha, why would I put my ear to a fuel injector when I could test it with a ohm meter.

So I did test my injectors with the ohm meter and the third fuel injector was definitely bad. Replaced it, runs like a champ again.

Thanks for everyones good advice.

[s13sr20chris]

Haha, why would I put my ear to a fuel injector when I could test it with a ohm meter.

sounds silly i know. resistance is good to know, signal is good to see, but you want to hear the pintle moving in the armature. that is an important piece of info.