Briggs And Stratton Backfires And Will Not Start . Some carburetors can induce backfire due to the sensitivity of internal transitional passages. The briggs & stratton engine may not start if the air filter is clogged. Litte help here Briggs 14 5 backfiring FunnyCat.TV from www.funnycat.tv If your briggs & stratton engine has a spark but won't run, then it is most likely a problem with the gas or air intake in the engine. I have to release the key and engage the starter to get it past compression stroke, then again, only turns one revolution. Fuel continues to pump to the engine after shutting down.