6 hp 4 stroke won't start

[Infinity]

Hi,

I've had issues with the fuel system, replaced the fuel pump, hose and bulb and and rebuilt the carb. The last time out on the water - about 3 weeks ago the bulb would not get hard and the carb was flooding and overflowing. I suspected that when I did the rebuild, some small piece of crap somehow got into it, so I pulled it apart. Yep. A little bit of something was keeping the needle from seating, allowing the carb to flood. Removed it and she started right up and ran great for two hours.

Today I went down expecting no problems and for the first time it would not start at all. Bulb got hard, and it popped a few times when I pulled the cord - but it really acted as if it was not getting enough spark. It has always started. I am now stumped. I pulled the plug and it was wet and dark, as if it was running rich.

Is it possible the kill switch is not letting current to the plug? Or do I still have a carb problem?

Thanks in Advance
Larry in Alameda

 

[pvanv]

Re: 6 hp 4 stroke won't start

Larry,

What manufacturer/model/serial? Guessing this is a Tohatsu/Nissan, possibly a 6B?

Why did you change the fuel pump? Was the motor "running out of gas" at high speeds? If it popped a few times, you were getting at least some spark. If the plug was soaked, you were getting much too much fuel. Maybe over choking. A new plug and less choke may fix the problem.

 

[Infinity]

Re: 6 hp 4 stroke won't start

Larry,

What manufacturer/model/serial? Guessing this is a Tohatsu/Nissan, possibly a 6B?

Why did you change the fuel pump? Was the motor "running out of gas" at high speeds? If it popped a few times, you were getting at least some spark. If the plug was soaked, you were getting much too much fuel. Maybe over choking. A new plug and less choke may fix the problem.

Yes its a Nissan NSF6A2. The engine performed great for years. Started reliably on two pulls and ran great. Last year it begin stallling at low idle, then began stalling out at wide open. Since it was running, and the plug looked good, I suspected fuel problems. Started by changing the inline filter, no help. Then thought perhaps the connector was allowing air into the system (there is constant air bubble in the fuel filter - is that normal?) so I removed the connector and plugged the line directly to the filter - using a new line and bulb. No help. After searching online for help, it seemed that the carb was suspect so I put a new carb kit into it, and replaced the fuel pump at the same time.

I've replaced the plug along the way also, but it did not seem to have much effect, which is why I suspected a fuel problem. I'll change it again and take your advise on the choke. Thanks

 

[pvanv]

Re: 6 hp 4 stroke won't start

Poor idle issues are typically varnishing in the idle and slow circuits of the carb. You need to make sure that you always run the carb dry at the end of each and every day to reduce that occurrence. Not unusual to get an air bubble in the filter. Quite normal.

If the motor stalls at wot, that's something completely different. Could even be water contamination of the fuel. You can drain the carb, flush the whole fuel system, and try fresh gas for that problem. If the plug is wet, you are not igniting, so you could have a (rare) ignition malfunction. In order to diagnose that, whip out the Factory service manual (not an aftermarket one), and using a good Analog ohm meter, test the ignition components.

Installing a carb kit is not a proper/complete carb service. If suspecting varnishing, you must do a complete tear-down of all bits of the carb (including the jets and the nozzle), and then do a 4-hour soak of every non-rubber part in real carb dip. Then blow out everything with a generous spray of generic carb cleaning spray. When you reassemble, verify proper float height.

 

[Infinity]

Re: 6 hp 4 stroke won't start

Poor idle issues are typically varnishing in the idle and slow circuits of the carb. You need to make sure that you always run the carb dry at the end of each and every day to reduce that occurrence. Not unusual to get an air bubble in the filter. Quite normal.

If the motor stalls at wot, that's something completely different. Could even be water contamination of the fuel. You can drain the carb, flush the whole fuel system, and try fresh gas for that problem. If the plug is wet, you are not igniting, so you could have a (rare) ignition malfunction. In order to diagnose that, whip out the Factory service manual (not an aftermarket one), and using a good Analog ohm meter, test the ignition components.

Installing a carb kit is not a proper/complete carb service. If suspecting varnishing, you must do a complete tear-down of all bits of the carb (including the jets and the nozzle), and then do a 4-hour soak of every non-rubber part in real carb dip. Then blow out everything with a generous spray of generic carb cleaning spray. When you reassemble, verify proper float height.

Thanks for the response.

I changed the plug and she started on the first gentle pull. It ran fine at the dock for about 10 to 15 mins., then stalled on idle, and what not start again. Acting like it had no spark. Frustrated I went home. The next day I went back and pulled out the plug, attached the cable to it and grounded it to the block. Gave the motor several strong pulls on the cord - no visible spark. Nothing. It seems some component of the ignition system has failed. That kind of makes sense as even when it was running, it seems to run "weak" - as the fuel wasn't fully burning.

From reading several posts, from people with similar problems, the CD seems suspect. How do I test that and the coil?
Thanks

So my next thought is

 

[pvanv]

Re: 6 hp 4 stroke won't start

Full diagnostic values are in the Factory service manual, Part# 003N210341, $40.00. You will need a good analog ohm meter to take readings.