Small Engines (Lawn Mowers, etc.): Gas edger runs only when primed, craftsman gas edger, briggs and stratton

Question
Ben,
any advice or suggestions would be great.  I have a Craftsman gas edger, has been used maybe 25 - 30 times at most, model number 536.772350 with a Briggs and Stratton engine, 4.5Hp, model number 10H902-0121-E1, which will not run.  Sorry that is not totally correct.  It runs when primed, however that is it.  I can start the engine but not keep it running.  I have repalced the spark plug, the oil was recently changed, and the fuel has also been changed, however since it runs, if only for a second or two, I was thinking it is something more complicated.
Any help/suggestions would be appreciated.
Anthony

Answer
Anthony

If your Engine will not start or is hard to start.
Possible causes:

  1. Fuel tank is empty or shutoff valve is closed, or fuel line or fuel tank cap vent is clogged.
  2. There is water in the fuel.
  3. Carburetor is overchoked.
  4. Carburetor is improperly adjusted or needs service.
  5. Ignition system or its wiring is defective or ignition switch is off, or timing way off (e.g., broken flywheel key).
  6. Deadman or other cutoff switch is open or defective.
  7. Spark plug is fouled, improperly gapped, or damaged.
  8. Engine compression is poor.

Sounds like you've got some debris plugging the fuel line somewhere...that's dropping off and then getting sucked up when it runs. That's why it runs for a brief time...then quits.This is a common fault and relates to the need for wintering an engine.
If fuel is left in the tank or carburetor over winter it will tend to form a gel like substance which floats around the carburetor and blocks the flow. In addition good care of gas is needed. Fuel starts to go bad after 3 or 4 weeks as it is aerated when leaving the pump. Always start a new year with new fuel.
Remedy. Remove the carburetor and clean thoroughly, also flush the tank and fuel lines with new fuel. Should remove the problem entirely.

Tip for wintering.
1. Empty the fuel tank
2. Start the engine and run until it stops

On some of those older 4.5 h.p. engines had to have a full fuel tank for the fuel pump to pull the fuel up into the carb. After it starts, it will restart if the tank runs dry, if you don't let it set too long! And, if there is a small side plate on the carb, held on by 4-5 screws, there is a couple of holes that might be clogged, or you might go get a new diaphragm for it! And, sometimes, water hides in the passageways under that plate! but my info is just in case your carb is like that! End result rebuild the carburetor.