Nissan 9.8A2 2004, 4 stroke, will not start

[Paulrusso]

As of today this motor will not start. In the last 2 months this motor went from,
- running like a new motor to...
- running rough (new plugs seem to clear that up) to...
- not wanting to start (starting spray would get it going) to...
- to not wanting to start almost immediately after starting on the first pull, to...
- starting fine hours or days after not starting but once again not starting later in the same day.
I have replaced the plugs, verified the spark and compression, replaced the fuel line, filter and pump bulb, cleaned the carb/replaced internal parts, the oil level is fine, etc.
Now the motor will not make an effort to start even with starting spray. Is the CD/power pack a suspect?

Any suggestions would be appreciated.

 

[MattFL]

Re-check spark and compression. Get a spark tester that will test spark while the spark plug is in the cylinder, and/or one of the testers with a big gap, so you can test the strength of the spark. It takes more voltage to spark in a pressurized cylinder than in open air, so that's how you want to test if the spark is suspect. Usually with starting fluid a motor will fire even with minimal compression, unless it's crazy flooded. Any chance that it's flooded?

 

[Paulrusso]

Thanks for the reply.

This morning the motor started on one pull and ran almost smoothly with the choke in. In the recent past it would generally only run with a full choke. My experience suggested that an air leak in the carb was causing that problem. Perhaps I fixed that issue with the cleaning/rebuild.
Today the motor ran at a fast idle for about 10 minutes and then slowly died. It will not restart so far today. The cylinder head is not overheated, the fuel bowl is full and it is pumping water. I checked the spark with an in-line tester and it looks normal but it won't start with starting spray. I don't have a compression reading (no assistant) but it feels solid to me.
Ebay has the C.D. for $40. I'm thinking that replacing it is a good place to start.

 

[MattFL]

Running with the choke is an important piece of information. You've likely got a fueling issue, or possibly an air leak. An air leak sounds unlikely, or the symptoms would be more consistent. My guess is either the bowl isn't filling with fuel, or the slow speed jet or plumbing is clogged up. Easy things first, next time it won't start or run, immediately check the bowl to see if there is fuel. If there's a drain screw, open it. If there is no fuel, then that's your problem. If the bowl has fuel, then it's time to disassemble the carburetor and clean it really good. Not just the parts you can see, but especially the tiniest passages. Use an ultrasonic cleaner if you have one, definitely put carburetor cleaner and air through every hole (wear safety goggles).