Nissan NS8B won't start

[C&C Eric]

... and yes, I checked the FAQ!

This one has me stumped. I think I've checked all the easy things, but here's the story:

I went out a couple days ago to check on the boat, and decided to give the engine a little run. It started great on the first pull, as usual, but then died after about 10 sec. Started right up again, and died after a few seconds. Now it won't even cough for me, like it's totally out of gas.

There's fuel in the filter, and when I took out the spark plugs they were wet, so fuel flow doesn't seem to be a problem. The plugs had a some surface crud, so I cleaned them off, but it made no difference. Holding the plugs against the block, they seem to spark fine. And I checked the kill switch -- open with the lanyard in, closed with lanyard removed. (I assume this is correct, but I guess if it weren't, then the plugs wouldn't spark either. ) And the fuel tank vent is open.

About a month ago I removed and cleaned the carb, because it wouldn't idle. (I didn't dip it, just sprayed and wiped everything I could get to. I didn't remove the main jet. ) About 2 weeks ago I replaced the fuel tank, fuel, and filters, and it was running great. It's E-10 87 octane fuel, fresh and clean.

If I look in the factory manual, the only things that seem to make any sense are:
- carb out of adjustment (possible)
- carb obstructed (unlikely, I think)
- several power head problems that I don't want to contemplate
- carbon accumulation in the cylinders (but it was running fine just seconds before.... )
- faulty spark plugs (maybe, but I think they're relatively new, and they are sparking.... I just bought the boat a couple months ago, and found a receipt for service that included new plugs. )

It seems to be acting like a fuel problem, but I don't think that's it, unless somehow it's so flooded that it won't do a thing, except that even when I left it to sit for a day it didn't go any better.

So like I said, I'm stumped. Even before I had to clean the carb it would always start on the first pull. Any suggestions on what to do next?

 

[TOHATSU GURU]

Re: Nissan NS8B won't start

Revisit the carb. It has to be dipped and allowed to soak in order to clean it. Mechanic in a can sprays only work as a preventive measure.

 

[C&C Eric]

Re: Nissan NS8B won't start

Revisit the carb. It has to be dipped and allowed to soak in order to clean it. Mechanic in a can sprays only work as a preventive measure.

Even though there's a big CAUTION note in the service manual not to clean the carb by submerging or soaking it in a carburetor dip cleaner?

If I do this, do I need to remove all the jets and nozzles first?

I guess I'll need to take off the fuel pump, too, which means $50 for a service kit....

And what's the right way to adjust the pilot adjust screw (and any of the other jets/nozzles that need adjusting)?

thanks,
Eric

 

[TOHATSU GURU]

Re: Nissan NS8B won't start

You have to completely take the carb apart. Everything. Then all the plastic and gasket materials go to your bench while all the metal components go into the cleaner for at least three hours. The manual will tell you how many turns out as your initial setting. And what service manual are you using?

 

[C&C Eric]

Re: Nissan NS8B won't start

And what service manual are you using?

The Tohatsu factory manual, from Helm.

Do you think the carb is flooding the cylinder, or not allowing enough fuel in?

I figured flooding wasn't the problem because it won't sputter even after it's sat for a day or 2, and I figured not enough wasn't the problem because the plugs are wet after I pull the starter a few times....

 

[TOHATSU GURU]

Re: Nissan NS8B won't start

Ignore the Helm manual. It was put together by Helm and then approved by Tohatsu. Yet another error in it. I would suspect that Helm has some old Johnson/Evinrude expert there who had a bad experience with carb cleaner. The Tohatsu original manuals don't have anything about using cleaner.

The engine symptom is broad and would lead me to believe that your fire is either weak or that the carb(almost always the culprit) is allowing too little fuel at the plug while at the start, throttle position. Your probably getting the wet plugs from over choking as you compensate for carb problem. Or you could have one of those problems you don't want to think about. Check your reeds while you have the carb off and check your compression before you do anything else. The inital setting on the air screw is 1 3/8 +- 1/4.

 

[C&C Eric]

Re: Nissan NS8B won't start

OK, thanks! I'll post my results when I get some....

 

[C&C Eric]

Re: Nissan NS8B won't start

I took the carb off and cleaned it, and now it's back to running great! It was pretty dirty again, after having just cleaned it a few weeks ago. I guess the fuel lines (which I didn't replace) still had a lot of crud in them from the old rusty tank I did replaced. Also, it seemed the the float valve was stuck closed, but then I wonder what would have been getting my plugs wet.... (Maybe it got stuck while I was taking it apart, turned upside down)

I think I still need to make some adjustments to the pilot screw. What does that actually do, anyway? Fine-tune the amount of idle fuel? There are ports, passages, and fittings all over that carb.... I would love to have an explanation of what they all do.

I also checked the compression. In both cylinders, it was about 60 psi after the first pull, and about 95-100 after the 3rd. (The manual says it's supposed to be 56.9 psi, so I guess just the first pull is valid. I wonder why it went up after more pulls? Seems like it wasn't exhausting)

Thanks again.

 

[marioscib809]

Re: Nissan NS8B won't start

change the spark plug even if the spark seems to be correct.
marioscib809

 

[ManLyn]

Re: Nissan NS8B won't start

I have the same problem on my 9.9 4 stroke NSF9.9B2 model. This thread helps, but is a carb difficult to remove and clean? I don't want to mess it up.

 

[TOHATSU GURU]

Re: Nissan NS8B won't start

If you don't know how I would let a dealer do it.