Small Engines (Lawn Mowers, etc.): lawn tractor wont stay running, craftsman lawn tractor, right fuel

Question
QUESTION: Hi Eric, I'll try and give as much detail as possible so please bear with me! :-) We have a Craftsman lawn tractor, 18.5HP B&S engine. This mower sat for a good 2 years, outside under a tarp. It was only 3-4 years old and ran fine when I parked it. When I moved in with my wife, she already had a mower that was garage kept so we always use that one. Recently I attempted to get this one going again, even if just to put a for sale sign on it. After some coaxing and charging the battery, I could actually get it to start, it would run for about 20-30 seconds and then cut off. It sounded normal as it ran but after 2 or 3 cycles of this it usually wouldn't start unless you let it sit. NOW, it wont even start at all unless you pour some gas or starting fluid directly into the breather, but it only runs a few seconds until that fuel is gone. I removed the fuel line going into the carb and saw no fuel when cranking. I put a new fuel filter on and had no change so i ordered a fuel pump, replaced that, and still have the same results and no fuel at the carb. I took the fuel line off where it enters the filter and i do have a trickle of gas coming from the tank. I think I understand that the fuel pump works on vacuum from the engine, and that line going to the pump looks fine, but if it was actually an engine problem that severe, would it run as good as it does when I spray starting fluid in it? I'd like to try and get it going and would really appreciate any ideas you may have. And your patience with me! lol. Thanks in advance.

ANSWER: Since it will start when primed you know the problem has to be fuel related...dirty carb or fuel pump.

Briggs fuel pump link:

http://www.briggsandstratton.com/engines/support/frequently-asked-questions/Serv

http://www4.briggsandstratton.com/miscpdfs/RNT/Carburetion_Troubleshooting_Detai

Check the fuel pump connection, the right hose connected to the right fuel pump nipple.  If you have a vaccum pump you can check the vaccum from the crankcase.  You can also remove the spark plugs, dis-connect the fuel pump pulse line, crank the engine and see you can feel the crankcase pulse.  It may be difficult to feel but a vaccum gauge will tell you for sure.

Regardless, I'm betting you will have to reomve, dis-assemble and clean the carb with compressed air from an air compressor and carburetor cleaner.

Let me know if this helps.

Eric

---------- FOLLOW-UP ----------

QUESTION: Eric, Thanks for the reply. I'm sure I should probably take the carb off and pretty much the whole fuel system as long as it sat. I'm a little puzzled though, if there is no fuel coming out of the fuel pump, does that kind of lead away from the carb as being the main problem? And if the engine isn't providing the vacuum to make the fuel pump work, would the engine run as normally as it sounds when I prime the carb? The fuel pump and fuel filter are both brand new, they were the easiest things I could change quickly, so before I start tearing things apart or buy any more parts, I'd like to think I was looking in the most probable places for the actual problems. Thanks again for the help and your patience. Have a great day.

Answer
Fuel pumps are pretty reliable devices but yes, you should have fuel pumping out of the fuel pump when cranking the engine.  Did you remove the spark plugs, disconnect the line at the carb, crank the engine and see if the fuel pump is pumping fuel to the carb?

The enigne needs to rotate fairly quickly to operate the fuel pump.  Usually this is not a problem as the engines starts quickly with the choke and the engine RPM increases to create vaccum to operate the pump.

If the fuel pump lines are connected properly then the fuel pump should work, since it is new.

Can you keep the engine running for a minute or two by priming it?  After a few seconds, 15-30 seconds, the fuel pump should be functioning.

Eric