OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 4.5 briggs starts but stops

Hi guys,i have a rover utility mower with a 4.5 briggs/straton for free.i cleaned out the fuel tank and carby-spark plug.on the first pull it will start and run for about 5 sec then stop,every time you pull it fires and runs as above and stops.good spark-clean fuel-auto choke works-i have read my b/s manual but now i am at a loss-any ideas would be appreciated...ken

Are you priming it to make it start? If so it sounds as if it is just running out the priming fuel then stopping. If you are not priming it, then it sounds like a flow restriction upstream of the main jet: some garbage in the system, or perhaps the fuel pump diaphragm if it has the usual small Briggs engine tank-under-the-carburetor arrangement. You can verify that it is fuel supply by continuing to operate the primer after it starts: if it keeps running, it is a fuel issue.

If you can make those checks and come back, we can get a bit further. At the moment, dirt in a carburetor drilling or a faulty fuel pump diaphragm sound the most likely.

Hi grumpy,this model has no primer-i have completely stripped the carby twice with the end result being the same,i will get e new gasket and try that.post pics and engine model num tonight...ken

Thanks Ken, it would help if we can verify that it is a tank-under-carburetor type. The picture should show that. Also, you could remove the air cleaner and trickle a small amount of fuel into the carburetor air intake while it's running. (stand clear of the carburetor in case of spits). If it keeps running, we will know for sure that the problem is fuel starvation. Once we are at that point, replacing the fuel pump diaphragm (between the carburetor and the fuel tank) and blowing through the various fuel passages in the carburetor are the main steps to take. Best to do the fuel-trickling trick before you buy the new fuel pump diaphragm, because if it isn't fuel starvation you'd be wasting your money.

Hi Mower man; I just went through a lot of drama with a similar Briggs and Stratton quantum engine. The mower would start and run briefly and then stop. After endless carburretor cleans the problem was found to be the "rubber" fuel line which had perished and kept flaking off bits of crap into the carburretor. Might be worth a check.

Here are some pics of the said mower,
rover utility---base number-1511
serial number-362097

4 h/p briggs-straton---model-110908
type-1201-01
code-82062404
Hope this info helps...ken

The engine is a tank-under-carburetor type, so the fuel pump consists of a rubberised diaphragm sandwiched between the bottom of the carburetor and the top of the fuel tank. Being rubberised cloth, it is not unusual for them to give trouble when they get old (like 28 years old, for instance). I suggest you follow my previous suggestion of trickling a little fuel into the carburetor air intake with the engine running, and see if it keeps running. If it does, the diaphragm and the carburetor internal passages need to be checked. If the engine stops anyway, even when you do the fuel-trickling thing, you may have an ignition fault. Incidentally the engine's top sticker says that it has Magnetron (i.e. no breaker points) ignition, which was introduced in 1982. This means you have no reason to remove the flywheel at present.

My comments don't apply as grumpy points out from the pictures there is no fuel line "like what I have got" on my mower.

your gonna have to take the carby and the fuel tank off the mower and give them both a good cleanout.

Ken,

From the pictures that you have uploaded I can see problem straight away and that is the oil bottle cap that is on the tank, it will cause a vacuum which will stop the fuel flow. The bet is the diaphragm will be stretched because it is working harder than it would normally.

Thanks bruce,the fuel cap slipped my mind.i will change it(the same thing happened to my boys mini bike(fuel tank cant breath)as in regards to the comment on fuel lines,its good info for other problem solving.i will attend to the mower and let you all know...ken

Thanks Bruce, and well done. I saw it was a non-genuine cap and didn't think any further. Lucky someone around here is on the ball, since I obviously wasn't. I had been having trouble working out why the pump diaphragm would work for 5 seconds then stop, but would recover in a short time. I'm hopeful there won't be any damage to the diaphragm, since it didn't run for long each time it started. Mower man will find out when he starts it with the fuel cap removed: if it runs properly, all he needs is a fuel cap from some junked Briggs engine.

Hi guys,sometimes you get so bogged down trying to rectify a fault,trying this and that with regular arobics pulling the cord when simple science comes involved.VACUUM caused by a non breathing fuel cap.loosend the cap,half a pull and wamo it kept running with a big smile on my face,adjusted mixture screw half a turn.I stopped and started the mower 10 times just to make sure,so thanks everyone for your thoughts and i owe you a beer BRUCE. ps-took my size 10 boot off and gave my-self a kick in the "but"...ken

Good to see that it was the problem. All you need to do now is get the correct cap.