4 HP Nissan ,,,need help

[Chuck7]

Hi Folks,
Got a question for the experts..My carb was filthy..I took it apart and it didn't go back right..so here's what i did from start to finish
I removed all gas lines..about 2 feet..it had gas lines going to either a portable tank or you could use the tank on the motor..
A. Removed all lines ..and ran one short direct line from tank to non return fuel valve ..to fuel pump to carb..
B Bought a new carb..
C. Bought a new Fuel Pump
D. new filter
E. The non return gas valve is on.
F. Vent is open

Motor starts on first crank...but after 1 minute shuts off..after brainstorming ...do I need to put all the gas lines back on to adjust the pressure/vacume? or what other possible reasons are there that it won't keep running?

Thanks ,
Chuck7

 

[pvanv]

Re: 4 HP Nissan ,,,need help

It would help to have your precise model/serial. You likely have an NSF4... either an A2 or B...

Regardless, you are using the "throw parts at it until it runs" or "shotgun" system of repair, which is the costliest way to fix a motor. Eventually, you hit the magic part, but you end up changing a bunch of good parts along the way.

Much better to do a proper diagnosis, with the aid of a Factory Parts Catalog, and a Factory Service Manual. Since you were unable to reassemble the carb correctly, it's possible that you could benefit from the assistance of a more-experienced mechanic. Your dealer can be your friend here. See http://www.nissanmarine.com/search/index.html for you local dealers.

The non-return check valve is used to prevent transfer of fuel (or air) between an external tank and the onboard tank. If running with a single tank only, it can come out of the fuel system for diagnostic purposes.

Does the carb actually run out of gas after only 1 minute? Doubtful, as these carbs typically take a few minutes to run dry. Opening the drain screw will show whether there is fuel in the bowl. Is the pump delivering fuel? You can check its operation by cranking with the fuel line at the carb disconnected.

If the original carb was "filthy", perhaps there was junk in the fuel lines and pump. If so, and that was not flushed out before the new carb was installed, that junk may have been pushed into the new carb.

Assuming you still have a clean carb, a proper diagnosis will likely show a problem somewhere other than the fuel system, since you have already changed out all the fuel system bits. Using the service manual, check the ignition and mechanical systems. You may find that the igniter/CD has a failure when hot. But you need to do a proper diagnosis, with the aid of a Factory service manual, before you have replaced every part on the motor.