280z #6 cylinder not firing

[SmokeyRoach]

All,

For some reason my #6 cylinder is not firing. To start the plug is wet when pulled out after running on the remaining 5. Injector is firing, spark is good on #6, compression is at ~178-180 on all, timing is right on. All my checks so far check out but it is still not right.

Any ideas how to further troubleshoot this?

Thanks

76 280z

Stock motor

[MikeW]

Wet with fuel or wet with oil?

[SmokeyRoach]

Wet with fuel.

[76Datsun280z]

From what you're describing, it almost sounds like it is firing as you say it's getting fuel, good compression and spark. Is it running really rough and choppy and you think it's not firing on number 6?

[KDMatt]

I know it sounds dumb, and I don't mean to sound like a patronus, but is your firing order correct?

It's been printed wrong in the past (esp. in the Haynes manual) ... so when you're doing your "checks" what are you using as your resource?

[MikeW]

Perhaps you should switch two plugs and see if the problem stays with #6. I'm not sure if the #5 wire will reach #6 but if so you could also try swapping wires. Admittedly I know next to nothing about fuel injection but is it possible that an injector can get stuck open such that it's always spraying? Can you also swap injectors and see what happens?

[sblake01]

How do you know the injector is good? Even if you're getting a signal to the connector, the injector could be just dumping gas instead of opening and closing. BTDT. You say you have good compression at that cylinder and you're getting a signal to that injector so the only thing that could be at fault is the injector itself. Can you hear it clicking? Is it the same sound as the others? I use a mechanics stetoscope to listen to them. That coupled with a little apparatus I came up with that consists of a 9 volt battery, some wire, a momentary push button switch, and an injector connector.

[Zs-ondabrain]

And as for #6 not firing. It can only be one of a few things.

1) a bad spark plug wire

2) a bad spark plug

3) bad cap or rotor (more towards the cap)

but you said that #6 IS getting spark. So which is it? Even if your injector is bad (stuck open or dumping too much fuel) a sparking spark plug should fire that fuel.

If it's NOT firing that fuel, it's time to upgrade your igniton system to a set-up that puts out some better fire power than what you're currently running.

I personally use a Mallory Unilite Distributor with a Mallory Promaster Coil and an MSD 6A. The coil puts out around 60,000 volts, or so I read somewhere and it puts out a bolt of Lightning each and every time if fires.

Something to think about.

[Mr Camouflage]

Not if the AF ratio is way out it wont fire. Too much fuel and it wont burn.

[sblake01]

Even if your injector is bad (stuck open or dumping too much fuel) a sparking spark plug should fire that fuel.

I also disagree with that statement having been through that. Same scenario and a new injector solved the problem.

[Fun_in_my_z]

The extra fuel fowls the plug....

[KDMatt]

The extra fuel fowls the plug....

Right. My injectors are leaky/stuck and the car still runs starts up fine and runs.

Weak spark is still my guess.

How's the dizzy cap and other stuff look?