The Mower Bench

[Sawchip]

Not a mower and not a chainsaw so picked this thread at random.

Went to start my 4 stroke Stihl brush cutter yesterday, it fired, revved up and then died. Thought I had flooded it so cleaned the spark plug etc, still no joy. Anyway later when I picked it up I noticed it leaking petrol, turns out I hadn't screwed the cap on tight enough. Have i drawn air into the system or something? Still couldn't get it started when I screwed the cap tight. Thanks

As a opener.....Been running this year ok before this ? If it has a purge bulb then air isn't a issue.

Reving up and then cutting out tends to be fuel starvation if the revs elevate before stopping iv found.

Edited May 13, 2016 by Sawchip

[Steve Bullman]

As a opener.....Been running this year ok before this ? If it has a purge bulb then air isn't a issue.

Reving up and then cutting out tends to be fuel starvation if the revs elevate before stopping iv found.

I use it for mostly personal use, its been sitting in the garage all winter. Hasn't been started for probably 6 months. Revs didn't elevate before cutting out.

[Sawchip]

I use it for mostly personal use, its been sitting in the garage all winter. Hasn't been started for probably 6 months. Revs didn't elevate before cutting out.

Fresh fuel ? Old fuel? sometimes it takes a bit to pull fresh through and get shot of the old ..Plug dry ? look to fuel issue ..wet..check for spark ? Change out the plug to eliminate..you can always put the old one back in once you get it running. Usual stuff before getting deeper

[Steve Bullman]

fresh fuel yes. I give it plenty pulls believe me! i'll check the plug but failing that will probably have to take it into my local dealer. Changing a bar and chain is about the depth of my mechanical knowledge

[Sawchip]

fresh fuel yes. I give it plenty pulls believe me! i'll check the plug but failing that will probably have to take it into my local dealer. Changing a bar and chain is about the depth of my mechanical knowledge

Just double check the basics...Fuel ,,spark and air. Make sure the start procedure is right . I eliminated flooding as you said it fired ,ran,stopped .If it was ok end of last year its more likely to be ok now unless there is a bad fuel line or plug. Its never easy coming up with guaranteed solutions "blind" but as it did "something " rather than nowt at all when you first went to start it i wouldn't think its to much to sort it

[Steve Bullman]

Cheers, will have a play tomorrow

[GardenKit]

Was it stored on petrol Steve? (as opposed to my favourite liquid)

 

When an engine starts first it is running on the fuel drawn into the carb by the purge bulb, but, when running, the internal fuel pump takes over (the 'pump' is in fact a diaphragm)

 

During storage, if using petrol, the fuel can go off and become gummy. This can block the internal filter and render the diaphragm valves inoperative so that the internal pump does not work. A carb overhaul will fix this.

 

Other, storage induced reasons, can be degraded fuel hoses and, or, impulse hoses,and gummed tank filter as well as sticking inlet or exhaust valves.

 

Hope you get it sorted.

[Steve Bullman]

Stored empty Barry

In me experience, machines with carb issues will start, they just wont run?

 

So having the cap loose has noting to do with this do you think?

 

Just to confirm, this is a stihl 4 stroke strimmer and not a stihl 4 mix

[GardenKit]

Even if stored empty Steve, the carb can still suffer from the degraded residues of fuel, and the diaphragms can harden and misshape.

 

And, exactly as you say, it may start (on the purged fuel) but not run as its unable to pump for itself.

 

Not many of those old four stroke Stihls around now Steve, if you get it sorted maybe you should include a can of Aspen 4 on your next delivery.

 

I can't see how having a loose fuel cap can effect it either.

Edited May 13, 2016 by GardenKit
another comment added

[carlos]

i have just sold a ride on ( 36" deck 12 hp b+s engine manual gears) it had been standing for a couple of years but started and ran fine, till the guy ran it today and said it konked and that fuel was leaking from around the carb and it wouldnt start????

so i said i could take a look so just after a few pointers of things to check.

thanks carl.