Nissan Repair: 90 Nissan 240 Missfire#3, volt ohm meter, head gasket

Question
It has the KA24E. I was driving around 35 mph and the car started to misfire. Found that #3 plug had fuel on it. Replaced plugs, wires, cap, rotor. Have pulse on NOID light. Recently replaced head gasket(2 weeks ago)and car did fine until this. I have also tested compression and am equal in all cylinders. I have checked and all vacuum lines are intact and connected. Is there any way I can test the fuel injector? Anything else I might have overlooked?

Answer
Warren,

You have done well in your diagnosis.  I would say number 3 injector is hung open and causing your problem.  Problem with a noid light is that it tells you that the injector is being commanded.  But, not that is is working internally.  But, the wet plug is a give away.  You could check the fuel pressure and test for leak down.  That is, turn the key on and listen for the plmp.  Watch the pressure gauge that you screw onto the injector rail and when the fuel pressure tops off turn the key off.  The pressure should hold for several minutes.  My bet is number 3 is leaking and the pressure will drop off pretty much instantly.  A wrecking yard is a great source for injectors.  You can test them with a volt / ohm meter for resistance and match the best ones and install them.  I have bought four for as little as $25 bucks at my local yard.  You will need new o-rings to install them.  But, if you did a head gasket you probably already have them.