No spark (1 cyl) on 1994 120hp Evinrude OB

[rustyscrew]

I am re-posting my questions that I had at the end of a long thread...my apologies but it seems like questions get lost otherwise.

Here is my last post, followed by the background info.

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Really helpful, thanks for all the ideas. So- threw some more hours at it today. I rebuilt the one of the carbs that feeds one of the bad cylinders and replaced the needle-valve seat. Seemed to run better. would idle ok and not die. That was an improvement but still did not fire on all cylinders.

I retested for spark...set tester to 3/8 and one isn't firing!

Ok so that is good to figure out. not sure what the problem is though because I replaced the connector from the computer to the coil. It was rusted. also replaced the coil with one I had around. still no spark....

Is there is a way to test whether the coil is receiving current? voltmeter?

making progress...

also fixed a corroded wire from the computer (port back screws inside the black plastic housing) I don't know what they are for but thought maybe they were a problem since its the same side as the bad cylinder.

So looks like the spark problem is the priority now. any helpful tips for diagnosing where the problem stems from?

thanks...the advice on this forum is so incredibly helpful

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Background:::::

Still wrestling with a problem that has me stumped

Engine: 1994 120hp Evinrude OB

Problem: Starts up fine, sounds like all cylinders. Runs for a 30 seconds or so then starts to cough. Loses cylinders and can run for awhile but pretty sure its running on only 2.

History: Was having hard starts but ran OK. Figured it was time for carb cleaning. Usually I would clean and not replace any parts and it would always run better. This time ordered the kits and replaced all parts. That is when the problem started. Since then I have tried everything I can think of and stuff that this forum has suggested.

I am pretty sure I lose the both left-side (port) cylinders because the new plugs were quickly fouled and wet after one 2 minute running. WHAT might cause both of those cylinders to be bad?

What I have done:
1) Rebuilt all 4 carbs twice.
2) Checked for spark (with proper tool)
3) Checked compression
4) Replaced plugs
5) Replaced inline and spin on fuel filters
6) Tried alternative gas tank directly to fuel pump
7) Tested fuel pump pressure (5 psi and holds indefinitely)
8) Spray fuel into carbs while running. I can keep all cylinders running this way. Hard to tell exactly which cylinders it responds to. Definitely top-port.
9) fixed a busted wire in the computer on top (didn't change performance)

I was about to redo the carbs....then felt like that may not be the problem.

Any thoughts?!?

thanks

 

[scrampbell]

Re: No spark (1 cyl) on 1994 120hp Evinrude OB

You can switch your power packs from side to side and see if your problem cylinder follows the power pack.