Tried to start after pulling over, no success. I had it towed home and check for spark, ok. I checked to see if fuel pump was working, ok. I check little air valve looking thing on fuel line in engine compartment and got fuel to squirt on ignition. I checked air filter, ok. I took off cover to top of carb, and primed w/gas, engine started for a little while. Is there a simple fix to this problem.