Cylinder not firing - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 33 (permalink) Old 08-20-2019, 11:43 AM Thread Starter
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Cylinder not firing

'75 Z, in the Dallas area. My cylinder #6 does not seem to be firing. This is after me doing some undercarriage pressure washing. At idle, when I pull the #6 plug, no change. All other plugs I can notice a difference. So this I presume would tell me that 6 is not firing. I have a new distributor cap and rotor. Spark plug wire seems OK, I can't see any problems with it. What else can I look for that would keep #6 from firing.

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post #2 of 33 (permalink) Old 08-20-2019, 12:19 PM Thread Starter
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'75 Z, in the Dallas area. My cylinder #6 does not seem to be firing. This is after me doing some undercarriage pressure washing. At idle, when I pull the #6 plug, no change. All other plugs I can notice a difference. So this I presume would tell me that 6 is not firing. I have a new distributor cap and rotor. Spark plug wire seems OK, I can't see any problems with it. What else can I look for that would keep #6 from firing.

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GT75Z
I just checked the injector, it sounds like all the others. Appears to be firing and I know it is getting power.

Scratching my head,
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post #3 of 33 (permalink) Old 08-20-2019, 02:03 PM
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so you can hear the injector clicking, you used a stethoscope I presume? and up pulled the plug out, connected the connector to it and can see is sparking right?
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post #4 of 33 (permalink) Old 08-20-2019, 03:19 PM Thread Starter
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so you can hear the injector clicking, you used a stethoscope I presume? and up pulled the plug out, connected the connector to it and can see is sparking right?
Yes, I can hear the injector clicking through my very long screwdriver. I have not pulled the plug to check for spark, I use to do that as a kid with my lawnmower but not sure the safest way to do that with the car. Seems I would have to run the engine without the plug in the cylinder and that doesn't seem like a smart thing to do. I have switched plug wires with another and get the same results so it is not the wire.
How can I tell if I am getting power/spark to the plug?

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post #5 of 33 (permalink) Old 08-20-2019, 03:21 PM
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Very common after pressure wash for water to get into distributor, which causes all sorts of weird and worrisome running until it dries out. Before you do anything, pop the dizzy cap off and check for water droplets. Also take off the individual wires (at the cap) and check for moisture.

Blow out with compressed air or just let it air dry awhile. Then put back together and try it.
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post #6 of 33 (permalink) Old 08-20-2019, 03:51 PM Thread Starter
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Very common after pressure wash for water to get into distributor, which causes all sorts of weird and worrisome running until it dries out. Before you do anything, pop the dizzy cap off and check for water droplets. Also take off the individual wires (at the cap) and check for moisture.

Blow out with compressed air or just let it air dry awhile. Then put back together and try it.
I was very careful not to spray the engine. I know the Z motors do not like water. So that is my bad. I popped the distributor and it is as dry as can be but still sprayed compressed air on it and letting it sit for a while. Is there a way to check for spark at the spark plug? or could the injector still be clicking yet not delivering fuel? I just redid the fuel system, cleaned all the injectors and everything was great till I did my little washing.
Note to self - no water near the engine, ever!

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post #7 of 33 (permalink) Old 08-20-2019, 05:48 PM
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Okay, just saw that this happened after a pressure wash, so thought it might be the culprit. Is there ANYTHING else you did before this problem popped up? At any rate, if #6 is not firing, it could be the plug or the injector. I would first look at the plug. I've had them just 'go bad' for no good reason. Switch out #6 plug with any other one. If no difference (#6 is still dead), then it's likely the injector. If #6 all of a sudden works but the other cylinder is misfiring, then it's the plug. Good luck and let us know what you find!
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post #8 of 33 (permalink) Old 08-20-2019, 05:49 PM
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Oh, and if it is a bad plug and you decide to get a new set (which I would), use ONLY NGK or Nippondenso. Z cars for some reason just don't like other brands.
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post #9 of 33 (permalink) Old 08-20-2019, 06:36 PM
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if the plug checks out, then yes an injector can become clogged, that it happened after washing the engine means its unlikely. BUT if you want to check it, get a 9v battery and some alligator wire test leads, pressurized the system with a fuel pressure gauge attached, engine off fire an injector with the 9v battery across the injector, watch the gauge, if its working the pressure should bleed off.
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post #10 of 33 (permalink) Old 08-20-2019, 10:49 PM
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Which is easier: spudding a fuel press gauge in the line, or just pulling the injector and firing it into a bottle?

Besides, the gauge method will tell you nothing about just how the injector is firing. It's possible that the valve is opening without spitting much fuel.

By the by, one gets a better picture of plug wire condition by checking (with a VOM) the wire's resistance value against the others.

Another by the by; have you yet actually pulled all the plugs to read/compare the tips? This is a better/easier/safer way to check plug operation, no? For example, after running, a wet tip on no.6 would tell you whether the injector is firing and whether the plug is not.

Just a thought...



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