Can a bad trigger/wire cause a cylinder not to fire?

[silverbullet02]

150 promax. Replaced almost everything on the motor except the trigger in which another is on the way. Coils, wire harness, stator, switch boxes, computers, injector, grounds checked, you name it. Even swapped injector plugs on 5&6. #5 keeps coming out wet with no burn on it yet on the trailer the timing light shows its firing. Weak fire? If the trigger doesn't do it I'm not sure what else there is. Any ideas? Thanks,

Brian

[Dave Strong]

Yes they can.

Dave

[j_martin]

However, a weak trigger usually drops 2 cylinders, opposite in the firing sequence, ie 2 and 5.

[Go Time]

You didn't mention checking compression on #5.....

[silverbullet02]

You didn't mention checking compression on #5.....

Same as the rest.

Im wondering if its not the trigger itself but a deteriorating or damaged wire from trigger to switch box.

[j_martin]

Short answer, yes, but unlikely.

In the trigger there are 3 coils. Each coil fires 2 cylinders on 2 wires. It's possible a partial short to ground on one wire would kill the trigger on the cylinder it's connected to without killing the opposite one, as that short would be functionally invisible to the other side.
Believe me. I don't have time to explain it to you.

Does the fault move if you swap switchboxes?
Does it fire if you remove the bias jumper between the switchboxes? Don't worry, it'll run fine that way for testing.

Between the trigger and bias circuits, these things can do pretty goofy things, where the "good" switchbox is in fact the faulty one.

[CharlieB53]

Have you done a spark test using a 7/16 inch gap?

What color is the piston dome of that cyl? Is it 'steam cleaned' and looking like clean aluminum?

[silverbullet02]

The fault hasn't moved with everything we've done. The trigger is about the only thing left that hasn't been touched, so we've got our fingers crossed.

Have not done a spark test. Piston is clean/wet (oil/gas) but it's a recent rebuild so it hasn't gotten a chance to carbon up yet with what's going on.

If there is a bright side, with a 150 that's down a cylinder, the boat still runs 70, haha!

[CharlieB53]

A DVA meter or a DVA adaptor for use with any meter, along with the CDI Troubleshooting guide makes short work of determining any ignition problem without simply replacing every component until it runs better.

CDI Electronics Practical Outboard Ignition Troubleshooting