How to Fix Briggs & Stratton Small Engine that Only Runs Off the Primer



Here is an instructional repair video for how to fix a Briggs and Stratton small engine that only runs off the primer. This applies to engines where the gas tank is attached directly underneath the carburetor.

While this video is intended to be informative and instructional, understand that your own repairs will be at your own risk.

Thanks for watching!

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29 thoughts on “How to Fix Briggs & Stratton Small Engine that Only Runs Off the Primer

  1. Really stuck here. Had the exact same issue as everyone else…would start from primer and then stop. Totally removed carb. Cleaned with carb cleaner and pipe cleaners to clean all ports and tubes. made sure too get holes in bowl plug. Changed out gas, and used rebuild kit and replaced gaskets and needle. mower started and ran great last night. when it got dark put it away and now doing exactly same thing today when tried to finish yard. Took back apart looking for any clogs or dirt, nothing… any ideas on what could still be the problem?

  2. I just bought a used Craftsman Eager*1 with a 6.5 B & S. The seller stated and demonstrated that he had to prime it up to 20 times before it would start. He had replaced the tires and blade and it is self propelled. I paid him $70 for it. From watching your video it would appear that it needs a diaphragm and gasket. The primer itself does not appear to have a crack or hole in it. I will do what your video has shown and expect a good result. Thank you for your great demonstration.

  3. By the way it will start(from a cold start) after priming it up to 25 times and it stays running. If i shut if off, i only have to prime it 3-5 times. Do you think i am on the right track in replacing the parts you did?

  4. Thank you for the very informative video. My lawn mower is running better than ever. The part number for the carburetor gasket was much appreciated. Excellent video!

  5. My Toro mower, with Briggs & Stratton engine, stalls after running for about 2 minutes. If I hit the primer button it starts right back up and runs about another 2 minutes. It doesn't stall if I loosen the gas cap every 1 minute and give it air. What might the problem be?

  6. I always find aluminum shavings in that top part. I think its machining bits or whatever. I have done tons of those diaphragm type carbs. Sometimes its easier just to replace the whole thing. $13 for a carb with gas tank. no muss on fuss. I only do that if they warp,which does happen from time to time. if they leak after reassembly,they warped,no fixing that. good video though.

  7. When I get grass clogged under the deck I push down on the handle then raise the front and slam down to knock grass out but when I do the mother nearly dies. It's stalls bad

  8. I have a 3.5 Briggs, starts but soon as the prime runs out it stalls…………….cleaned the carb and replaced the carb diaphragm but it still dies after start…………Can anyone help??

  9. Gotta love helpful youtube videos. Thanks for this! My briggs/craftsman power washer had this problem. $3 gasket and diaphragm from NAPA and I'm back in business.

  10. New mower does same thing runs 2 seconds and shutts off just used one time and kept in garage for a month and now it's not running any ideas?

  11. it just goes to show that anybody can make a video nowadays. after working on small engines for years, the reason why they only run using a primer bulb is because they are left outside and they get rain / water into the gas tank. if it was actually the gasket seal located between the gas tank and intake assembly… It would idle up and down erratically until replaced. the reason for this, is that the ethanol Harden's the rubber gasket portion and it no longer functions properly. So, keep your lawn mower undercover or in a shed such as a garage and keep rain water out of your gas tank. Sometimes, a little fuel treatment will emulsify the water and burn with the gasoline. But if there is too much water in the tank , the contaminated fuel must be dumped out. This process will save you approximately $7 + 15 minutes of your time for replacing something that is not needed

  12. Thanks for the video. My mower started surging and then eventually died. Only ran for a few seconds when primed. Fresh gas. Swapped out the carb diaphragm and she's running great.

  13. Thank you so much, I saved myself minimum $140 by finding the parts I needed to complete this repair which thanks to your video was easy to do! You are great, thanks for sharing!

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