97 Safari #5 cyclinder misfiring HELP !!!!

[safari crazy]

I have a 1997 gmc safari 4.3 vortec with the w engine 98,000 miles. I've replaced the cap, roter, plugs ,wires and the #5 fuel injector. The check engine light is on and p0305 is the code. Did a compression check on it that also seemed fine. Pulled the valve cover and checked the springs,lifters,push, rods ,etc. that too seemed fine. Any help would be much appericiated.

Thanks.

[old_master]

What brand of parts did you use? What did you gap the spark plugs at? Make sure the plug wires are installed correctly. On the distributor cap, driver side front to rear, the wires are: #3, #1, #5. On the passenger side they are: #2, #4, #6. Some distributor caps have the cylinders numbered on the cap at each position, some don't.

[safari crazy]

The misfire started before I did the tune up. I did the tune up hoping to fix that problem. Just odd after doing that the same cylinder with the same misfire.

[old_master]

Check fuel pressure, paying close attention to leak down. 60 to 66psi key on engine off. Pressure must remain above 55psi for several minutes. This will test for a possible leaking injector. Pull #5 plug and see if it's getting fuel, it should have at least a residue of fuel on it. That will tell if #5 injector is opening. If it's dry, the injector is not opening.

[safari crazy]

Originally Posted by old_master

Check fuel pressure, paying close attention to leak down. 60 to 66psi key on engine off. Pressure must remain above 55psi for several minutes. This will test for a possible leaking injector. Pull #5 plug and see if it's getting fuel, it should have at least a residue of fuel on it. That will tell if #5 injector is opening. If it's dry, the injector is not opening.

I pulled the plug it looked dry is there some way to test the 12 volt/ ground pulse on that injector coming from the control module. I tried to do it with a test light, the pulse must be to fast.Is there a fuse that goes to each injector.

[old_master]

Before getting too involved or jumping to conclussions, make sure there are no vacuum leaks on the engine, especially on the #5 intake runner.

There is one fuse that protects all 6 injectors. The pink wire from the PCM to each injector is hot in the START and RUN key positions. The #5 cylinder driver circuit wire is black with a white tracer. Each time the PCM applies ground to that wire, (inside in the PCM) the circuit is completed and the injector opens. DO NOT use a 12v test light. A noid light is the safest and easiest way to test for pulse on the black/white wire. If you connect a voltmeter between the black/white wire and ground, it should show battery voltage when the injector is off and zero when it is on. If the pulse is present, the problem might be a faulty or a stuck poppet valve, or a faulty #5 injector, (just because it's new, is no guarantee that it's good.)