No start problem on Nissan NSF 9.9B

[km1125]

This thread was called "ABS - Auto By Starter.. how does it work?". I changed the title in case anyone was searching for help with a no-start issue on these motors.

I picked up a NSF-9.9B and could not get it to start. Checked everything, cleaned carb, replaced plugs and could not get it to fire at all. Would fire if I sprayed carb cleaner in the intake.

Since this is the first time I've dealt with one of these motors that had an "ABS" device instead of a choke, I posted this question:

A new-to-me NSF-9.9B has an ABS or "AUTO-BY-STARTER" on the carb instead of a choke. I'm wondering exactly how this works. I understand it richens the mixture just like a choke, but how does it function? Does it start off un-activated and allow more gas to flow, then when voltage is developed in the charger circuit apply voltage to the ABS to cut off then extra gas when it thinks the engine is warm enough? (or does the CD module do this?)

 

[pvanv]

Yes, it is thermostatic. It has a heater in it, and when the motor runs, the heater causes the pin to extend, leaning the mixture.

 

[km1125]

Thanks for the info Paul, - that makes a lot of sense. Do these things go bad? If they went bad, would they just make the engine run rich, or make it hard to start because they don't richen when cold?

On this motor (NSF-9.9B) I was having trouble starting it. I cleaned the carb and fuel pump, although both looked pretty good. Since I was already planning on upgrading it, I went ahead and got the 18 HP carb. Put that on, and it starts and runs nice. Took the old one apart again and could not see anything on it, but I dipped it for a couple hours anyways and cleaned everything. All the passages I could find had flow. Put it back on and still had a no-start. Out of curiosity, I swapped the ABS from the 18HP to the 9.9, but it did not make any difference. Put the 18HP back on and it runs nice

 

[km1125]

No Title

OK, so I figured out what the problem was. There is a small passage in the base of the float bowl. This feeds the reservoir for the ABS device, and on the larger motors where you have an accelerator pump (the 9.9 doesn't have one), then it also feeds that reservoir too. Found out this was clogged even after I had soaked the parts in a dip carb cleaner. I may have been able to dip it a few times and eventually get it cleaned out, but I ran a small wire through there while I was squirting carb cleaner, plus I blew through it with compressed air. I guess I did not check this passage before, as I was thinking the problem was in the carb body itself.

What I also discovered is that this passage will NOT drain when you drain the float bowl, because it has a lip above the base of the bowl. Further, if you were to run the engine dry, I don't think this would even empty this, as this passage is primarily used only during cold starts. However, if you have a 15 or 18 HP, the accelerator pump is also fed from this circuit, so while running the engine dry I would quickly throttle a few times as the engine is getting to run out of gas and then maybe a few more times after.

What's kind of silly is that the Tohatsu would have drilled from the bowl drain direction, then this would have drained when you pulled the drain plug. It would have also eliminated one step in machining.

 

[pvanv]

The carb must have sat for some time. Yes, that is a common issue on the 9.9/15/18 with ABS (B models). I have had to actually change the carb bowl on really bad ones.

As an aside, the 18B had a different cam (higher lift). Does the 18 hp carb work OK at WOT, or does it bog?

 

[pvanv]

As an aside, the 18B had a different cam (higher lift). Does the 18 hp carb work OK at WOT, or does it bog?

 

[km1125]

I have not had a chance to put the motor on the boat and open it up. Will have to wait till next year for the sea trial!

 

[Turbosl2]

I know this thread is 1yr old but i have had this issue since 2002 when the motor was new. Engine will not start without ether and it still struggles to run well. I cleaned the carb twice and didnt notice anything. Was this passage the fix? I have a 2002 NSF 3 B 18HP with this exact carb, just the enrichment circuit.

 

[km1125]

Yes. I did buy a new carb to get to 15HP, but I cleaned out the old carb and it works great too. The passage was VERY hard to get clean. Just soaking it would not do it. You need a small flexible wire to work through the passage from both ends to get it clean

 

[Turbosl2]

Ok thanks i will try it, i can tell you my reservoir on my 18HP has some sort of plug in it. I will post a pic, it is not clear and open like yours, but the exact same style carb

 

[km1125]

Yes, it is likely the issue. It is a pain to clean that passage, you can't just spray through it or soak it. You need a small flexible wire to poke though there from both ends until it's clean.

To answer Paul's question: I have not noticed any lag, but I didn't have a good chance to run the motor this year. The larger dingy I had it on had some problems with leaks, so we didn't use it much.