Combustion Problem?

[Panhandle Nick]

2009 4Stroke 15hp. NSF 15C. Nissan
I have spark. I have fuel out of the fuel pump i have fuel in the bowl of the carb. With the carb off, in my hand, with fuel in the bowl simulating throttle, i can see and hear the fuel being injected into the carb throat. Yet this motor will not fire off and run. I did follow the advice of one poster and remove the plugs and squirt fuel into the two chambers, replace plugs, prime fuel line bulb and attempt start. It did something it had never done before, the starter spun up and then the solenoid dropped the gear from the flywheel. Previously it would just crank and crank and never start so that gave me hope that it was a fuel problem. But after removing the carburetor and visually inspecting how it squirts fuel I have my doubts. What could this possibly be?

 

[racerone]

How did it run for you last season ?-----Or is this a new to you motor ?-----Checked belt timing ?

 

[Panhandle Nick]

It's new to me. I didn't think to check belt timing. This motor looks brand new and the belt looks brand new. Could it have jumped somehow?

 

[Panhandle Nick]

Here's a picture. I see an arrow in the casting of the block and a dot on the cam gear. I lined that up with another mark on the flywheel. I don't have information on how to time it

 

[racerone]

Clean the carburetor.

 

[Panhandle Nick]

Clean the carburetor.

Hello,
I cleaned it once, then when i came to a dead end on spark problems i re visited the carb and cleaned it again. It looks like a brand new carb and is crystall clean.

 

[racerone]

But your " like new " motor is not running !----Time for some orderly trouble shooting I say.

 

[Panhandle Nick]

Yes indeed. As you read my original post, I've done some troubleshooting. What might be missing?

 

[Panhandle Nick]

Clean the carburetor.

In my original post, what tipped you off, that i need to clean it the third time?

 

[racerone]

You say your motor looks like new with good spark.-----It must have spark at the right time.----Must have compression.----Must have fuel.-----The carburetors on these motors have tiny passageways.-----Perhaps look at carburetor again.

 

[pvanv]

what method did you use to clean the carb?

 

[Panhandle Nick]

I carefully disassembled it. Cleaned all the passage ways and made sure the float and needle were working properly. I can see it injecting fuel into the throat when i move the throttle by hand with the carb on my bench. Could it be injecting fuel into the carburetor throat but still have something wrong with it?

 

[km1125]

Spray some starting fluid or carb cleaner into the carb when you're trying to start. If it starts and tries to run - even a little bit - then you know you have carb or fuel issues and not ignition, compression or really anything else. In the bottom of the fuel bowl there are some tiny passages that go from one part of the bowl to another. Are you SURE those are clean?

 

[Panhandle Nick]

I did get some starter fluid but very difficult to get it in the carb throat due to the design of the intake housing I would call it, but with what little it did get, it cranked and did not start but the starter solenoid released as though it wanted to start (dropped away from the flywheel ring gear). In previous starting attempts the starter would simply endlessly turn the ring gear until I took my finger off the electric start button. I don't know why this is. I'm going to attempt rigging something to get the starter fluid into the carb and try again. Thanks for the picture, I could take another run at those passages, but I believe I've thoroughly cleaned them both times I've had it apart. Also I've not got an answer yet as to why I can move the throttle arm and fuel does indeed squirt into the carb throat. That would seem to indicate the carb is working fine.

 

[pvanv]

Pumping and squirting shows the accelerator pump is working. It does not indicate there is a good low speed circuit. Only a proper soaking and then a blow out will clear that.

 

[Panhandle Nick]

Pumping and squirting shows the accelerator pump is working. It does not indicate there is a good low speed circuit. Only a proper soaking and then a blow out will clear that.

Ok, wouldn't i at least get an initial startup? If the low speed circuit was clogged

 

[km1125]

Hold your hand over the carb opening when trying to start. THAT would mimic an 'old school' choke and you might start just fine. With the ABS, all it does is richen the mixture for those first few minutes but doesn't block any air like the old chokes used to do. The passage in the bottom of the carb bowl feeds the low speed circuits that pvanv is referring to.... it's the choke (ABS) and the idle circuits.

 

[MattFL]

Get a fire extinguisher and a can of starting fluid. Open the throttle, spray in some starting fluid then try to start it at idle or with some throttle. If it starts and runs for a moment then mechanically and electrically you're likely good-enough to run and you most likely have a fuel problem. If you have a buddy, let them work the throttle while you spritz it now and then with the starting fluid to see if it will stay running for several seconds. Just be aware that starting fluid is super flammable. If it runs that way, then focus on the carburetor. I would second what @pvanv said above about soaking and blowing. To really clean out those tiny passages, you will have the best results by soaking it in a hot ultrasonic cleaner for a while then following up with compressed air and carb cleaner through every hole and passage (wear goggles). Repeat a couple of times.

 

[Panhandle Nick]

Hold your hand over the carb opening when trying to start. THAT would mimic an 'old school' choke and you might start just fine. With the ABS, all it does is richen the mixture for those first few minutes but doesn't block any air like the old chokes used to do. The passage in the bottom of the carb bowl feeds the low speed circuits that pvanv is referring to.... it's the choke (ABS) and the idle circuits.

I think on this motor i have the old school choke. It's just a lever that opens or closes it.

 

[racerone]

Get a fire extinguisher and a can of starting fluid. Open the throttle, spray in some starting fluid then try to start it at idle or with some throttle. If it starts and runs for a moment then mechanically and electrically you're likely good-enough to run and you most likely have a fuel problem. If you have a buddy, let them work the throttle while you spritz it now and then with the starting fluid to see if it will stay running for several seconds. Just be aware that starting fluid is super flammable. If it runs that way, then focus on the carburetor. I would second what @pvanv said above about soaking and blowing. To really clean out those tiny passages, you will have the best results by soaking it in a hot ultrasonic cleaner for a while then following up with compressed air and carb cleaner through every hole and passage (wear goggles). Repeat a couple of times.