GT-150 electronics troubleshooting

[qcernie]

A little history. This is a 1990 Johnson GT150 crossfire Model # J150STLESB. Last year it developed a no spark on any cylinder. Tested with a 6 cylinder spark tester with the plugs out. Took it to the pros and they replaced the wiring harness, key switch and kill switch. After a couple of trips to the lake, the same symptoms appeared again. I replaced the stator, and the pack. Also took the engine wiring harness apart and inspected every connection. Sometimes (but not always) I can disconnect the red plug at the harness and jump the solenoid and get a spark. Then (this is where it gets strange) I can connect the harness back together and get spark using the key switch. It will start several times, then for no reason that I can tell, it goes back to the no spark situation. I went through the CDI troubleshooting guide and all test were within spec.1st time I tested resulted in the no voltage in the previous post. Went out and retested and now have 235 volts. May not have had a good connection with the back piercing probes the 1st time. I'm about ready to scrap this motor and look for a replacement but I've got so much time and money in it now. Anybody have any Ideas? I'm pulling what hair I have left out.

 

[Bosunsmate]

neutral start switch?

 

[emdsapmgr]

You've tested for spark with the red plug disconnected, by jumping the starter direct. That's a good test to eliminate the key switch and control box harness as a potential problem circuit. Even doing that, you still wind up with a "no spark" condition sometimes. That means the problem is still on the engine itself. You have really not mentioned the timer base. It also puts out voltage at cranking rpm's. They put out at least 0.3 volts when cranking. Anything less than that and it is condemned. How does yours test? You'll need a special "peak-reading" voltmeter to measure this voltage. Also, the engine must crank at least 250 rpm's in order to fire the ignition system, so be sure you have a good battery and starter.

 

[emdsapmgr]

You've tested for spark with the red plug disconnected, by jumping the starter direct. That's a good test to eliminate the key switch and control box harness as a potential problem circuit. Even doing that, you still wind up with a "no spark" condition sometimes. That means the problem is still on the engine itself. You have really not mentioned the timer base. It also puts out voltage at cranking rpm's. They put out at least 0.3 volts when cranking. Anything less than that and it is condemned. How does yours test? You'll need a special "peak-reading" voltmeter to measure this voltage. Also, the engine must crank at least 250 rpm's in order to fire the ignition system, so be sure you have a good battery and starter. When you've had the flywheel off (it's the vented 35 amp type) how do the magnets look inside the outer ring? Any cracked, missing?

 

[qcernie]

Took the flywheel off and checked all of the magnets for cracks and location and checked the wires. All good. The plastic on the outer bottom edge of the timer base was a little ragged. The flywheel key seems to not protrude much at all. Less than 1/16". I would have thought it would stick out a little farther. Put it all back together and now have good spark on all 6. I dunno.

 

[emdsapmgr]

Run it on the water under load and see how it performs. Those keys normally don't stick out very far.

 

[qcernie]

This morning started right up on muffs. Idled smooth. Let it idle for about 15 minutes with no hiccups. This evening, no spark on any cylinder. Guess it's to the shop. I can't figure it out.