Onan Gen Set 5000 very rough start
I have an Onan Gen Set 5000 generator in my 1994 Winnebago Class A motorhome. We were traveling last night from Michigan to North Carolina. I started the generator when we left home and it ran great ...
Forum Discussion
When a gasoline engine emits black smoke, it usually means that there is too much gasoline going into the engine. This is caused by the carburetor or air filter.
A clogged air filter will choke off the air inlet to the carburetor causing it to put out too much gas. Check or remove the air filter for testing.
A stuck choke will choke off the air inlet to the carburetor. When the engine is not running, the choke will remain closed, and is held by a spring. When the engine starts, the choke will be pulled open by engine vacuum. There will be a round diaphragm near the carb. A small rod will connect the diaphragm to the choke, at the inlet of the carburetor. A small vacuum hose goes to the diaphragm. Make sure that the choke, a small plate in the inlet side of the carburetor, rotates 1/4 turn freely to open and closed. When you try to start the engine, the choke will usually flutter from the vacuum pulses, and then open all of the way when the engine is running. If the choke does not open, the engine will get too much gas and either emit black smoke, or quit running. The diaphragm can go bad and need replacing, or the small vacuum hose can dry out and crack or break. You can clear out a generator engine that has been flooded by gas by holding the choke wide open and then trying to start it.
A carburetor float, that does not float, can cause too much gas to enter an engine. The float in a carburetor works the same as a float in a toilet tank. It regulates the level of gas in the bowl of the carb. As a float gets heavy from a leak or absorbing gas, it allows the gas level in the bowl to rise too high. This makes the carburetor put out too much gas to the engine.
The float operates a valve that controls the amount of gas coming into the bowl. If the float valve leaks, the carb will usually overflow gas when the engine is not running, and you will see it dripping or running out of the carburetor. It can also make the carburetor put out too much gas to the engine.
A bad sparkplug, a dirty carburetor, or bad gasoline, could be the problem too. I hope this helps you get it going.
A clogged air filter will choke off the air inlet to the carburetor causing it to put out too much gas. Check or remove the air filter for testing.
A stuck choke will choke off the air inlet to the carburetor. When the engine is not running, the choke will remain closed, and is held by a spring. When the engine starts, the choke will be pulled open by engine vacuum. There will be a round diaphragm near the carb. A small rod will connect the diaphragm to the choke, at the inlet of the carburetor. A small vacuum hose goes to the diaphragm. Make sure that the choke, a small plate in the inlet side of the carburetor, rotates 1/4 turn freely to open and closed. When you try to start the engine, the choke will usually flutter from the vacuum pulses, and then open all of the way when the engine is running. If the choke does not open, the engine will get too much gas and either emit black smoke, or quit running. The diaphragm can go bad and need replacing, or the small vacuum hose can dry out and crack or break. You can clear out a generator engine that has been flooded by gas by holding the choke wide open and then trying to start it.
A carburetor float, that does not float, can cause too much gas to enter an engine. The float in a carburetor works the same as a float in a toilet tank. It regulates the level of gas in the bowl of the carb. As a float gets heavy from a leak or absorbing gas, it allows the gas level in the bowl to rise too high. This makes the carburetor put out too much gas to the engine.
The float operates a valve that controls the amount of gas coming into the bowl. If the float valve leaks, the carb will usually overflow gas when the engine is not running, and you will see it dripping or running out of the carburetor. It can also make the carburetor put out too much gas to the engine.
A bad sparkplug, a dirty carburetor, or bad gasoline, could be the problem too. I hope this helps you get it going.
