Briggs 3.5HP starts then dies (Yes, diaphragm was replaced)

[domnatr6]

So ready to bang my head up against the wall trying to fix this myself. The engine code is 098902-1110-B1 and it's mounted to an MTD edger if that matters. I have now replaced the diaphragm three times, replaced the carburetor, cleaned every fuel orifice that I can find and put fresh fuel in it numerous times.

What happens is I'll prime it, pull the cord, it starts for about 2-3 seconds, then promptly dies. I'm not sure where to go at this point as I'm tired of throwing money at this and would like a more logical path to fixing the issue. Please help!

--CDM

 

[Rivets]

These carbs are so simple I don't know what you could have missed. I know you probably have done this, but at this point here's what I would do. First, pull the carb one more time and observe the following. 1. Are the carb gasket and diaphragm mounted correctly, Diaphragm against the tank and gasket against the carb. 2. Is there a spring between the carb and the diaphragm? 3. Does the small tank under the carb have fuel in it? If all least are correct, remounting the carb on the tank and then tip the tank slowly to see if fuel leaks out between the carb and tank. You just tip it far enough to get fuel in the gasket area. If any fuel leaks out try retightening the screws and test again. If it leaks, you have a warped tank. Replace the tank or try sealing all around the carb. I have had very limited success doing this. Section three of this manual might help.

https://dl.dropboxusercontent.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf

 

[domnatr6]

Thank you very much for the link to the service manual. Very helpful! So, in disassembling and reassembling this thing numerous times, I'm pretty sure I've gotten the gasket placed properly at least once. The issue seems to be that the condition hasn't changed, even with a carburetor change that included a new gasket, new spring, new screen. What I haven't checked is the leaking gasket scenario, but I highly doubt it since I would have noticed this when removing the tank to remove the carburetor.

I have not noticed if the little well below the carburetor is filled with gas when I remove the carburetor, I will check that. If it is not, what does that mean?

This all said, is there a possibility that this is not a fuel issue and the problem could be elsewhere? Something else that could be causing this that I can check?

--CDM

 

[domnatr6]

Well, bit of good news! Took the carb off again as suggested and there was fuel in the bowl. Straightened the gasket out to make sure there were no creases and blew the jet out with cleaner. Mounted everything and it started right up and KEPT RUNNING!!

I have no idea how this is possible with a carburetor change and a gasket change 3 times. Either way, we'll see how it goes in the long run. Season is coming to an end so probably won't get much use after I trim the abhorred grass overgrowth since the edger has been out of commission.

Thanks for the help and especially the service manual!

--CDM

 

[Rivets]

Glad to be of some help. Good luck.

 

[Johns_Pop]

I've got a BRAND NEW Murray doing the exact same thing. I cut grass with it one time and everything was fine. Went out to cut grass today and it won't run. I prime it and crank it and it runs for 2 or 3 seconds. Then it dies. I can't believe this on a stinking brand new mower. I don't know if Walmart will take it back or not.

 

[cuengineer]

I had a similar problem with an almost new B&S 6.5 hp engine lawn mower. I could pump it 3x and would crank, run fine for a few seconds, and cut off. I finally took off the air cleaner and happened to pull the starter cord and it ran fine until I cut it off. I put the air filter back on and it did the run for a few seconds and cut off again. It really did not look very clogged and had only been used to cut grass about three times so really surprised me. I think it must have been somehow defective on the inside. So you might do a check of this before going too extreme. Good luck!

 

[Johns_Pop]

I took the air filter off first thing to make sure it was not clogged. I prefer the pleated paper filters to the cheap foam one that was in there, but I can't get it to run without the filter either. I tried it today and couldn't even get it to crank off the prime. I *finally* did after fiddling and fiddling with it, so I'm back to square one. It'll run about 2 or 3 seconds off the prime and then die. I guess if no one's got the "magic answer" I'll start pulling 'er apart.

 

[Fish]

Can you keep it running by hitting the primer bulb before it dies? You should be able to, if not, let us know.

 

[Johns_Pop]

I'll give that a try when I work on it today. I hate those stinking "auto cutoff bars" that's on everything now. :thumbdown: