Lawnmower starts and cuts off

[xd400]

Hello Everyone,

I wonder if anyone can help with this.

I have a year old Challenge Petrol Lawnmower which starts but then cuts out after a second. I have to press the priming pump a good 5 to 8 times each time as well. As if fuel is not continually getting to the carb.

Oil is okay. Spark plug looks fine. Petrol is a few months old but has stabiliser added. Normally with stale petrol it won't start at all.

I did see a video showing this same issue and the cure was to remove the float bowl, clean out and crucially clean out the small hole in the retaining bolt. Now, this mower has a retaining bolt and an additional bolt (which I presume is for draining) but neither has a hole in it.

Any ideas? Thanks.

 

[Burnerman]

If you could post a pic of the engine priming pump side that would help......there's been so many different engines fitted to these machines!
The chances are, a new diaphragm and gasket is required that fits between the carb and fuel tank but a pic will be useful.
If the engine has a Tecumseh unit (black primer button) then the float bowl indeed has to come off, that's a different system altogether.....and the main jet holds the float bowl on too.
John

 

[xd400]

Hi John,

Thanks for your reply. I've had a closer look and the engine is a Chinese SV150. It has a red priming bulb at the front. And a spark plug at the front too. It's not had much use. Probably about 3 hours.

 

[Burnerman]

Ok, with you now!
On these carbs, the red fuel primer shoots a jet of raw fuel straight down the carburettor choke, just to help with a cold start. It's imperative that the gasket between the air filter inner part and the carb is in good order - if it isn't, the pump action of the priming bulb simply doesn't work. You should see the squirt of fuel if you remove the air cleaner and peer in.
If that's ok, it's float bowl off to check the condition of the components within. Undoing the bottom nut will allow the float bowl to come away. Sometimes this nut contains the main jet which is cross drilled through the brass - in other designs the main jet is screwed into the aluminium of the carb itself.....in fact, further up from the bowl nut if you follow!
Can you get an aerosol can of carb cleaner before you delve inside?
John

 

[xd400]

Thanks, John.

I think the priming is fine since it only fires when I do prime it but I will check.

The bottom nut doesn't have the hole so will have to investigate further on the weekend.

 

[DaveHerns]

Try some fresh petrol before you rip it apart. You may be lucky. I have a very old strimmer which wouldn't run till I changed the fuel