Lawn Mower Problem

[percyveer]

Morning all. My petrol mower has developed a problem. I fill the tank and after mowing the lawn the tank is empty. Previously the full tank lasted for many cuts. There is no sign of petrol in the garage where the mower is kept nor is there a trail of petrol on the grass. Mysterious! Any suggestion/ideas very welcome. Thanks.

[murraymints]

maybe one of our petrol heads can help..Tonyav might be the one to help ..will point him here ...something to do with the choke maybe ?

[Hypognosis]

@percyveer

In no particular order

1. Full tank, Fuel tap closed, filler cap tightened. Check level via dipstick, recheck hourly until satisfied no leak in the tank or cap.
2. Fuel tap open. Visual check for leaks in the tap structure.
3. Ditto, checking for fuel line splits.

Having eliminated fuel leakage, the loss could be just high fuel consumption

1. Spark plug fouled or wrong gap, or not tight on the threads?
2. Is it 2-stroke or 4-stroke?
2b. Lubrication method, if 2-stroke?
3. Engine tune up (£££, last resort)

Far more likely is wear and tear or fouling in the bearings of the transmission and blades - resistance to rotation which you might be able to feel. Cleaning and lubrication might sort that out.

Otherwise, someone is siphoning your tank, when your back is turned.

[alavahalf]

If their is no sign of a fuel leak .. the most likely fault is your choke may be stuck closed. This would cause the fuel consumption to rise dramatically.

You haven't said what type or model of lawnmower you have, that would help.

In the vast majority of cases it would mean simply removing the air filter and squirting some carburettor cleaner into the choke chamber. The choke flap should move easily.

[waterboatman]

The air filter might well need cleaning/replacing. A common cause of your symptom. It will also result in the engine getting fouled up.

[percyveer]

Thanks folks. It is an Alko petrol mower. It was running ok while cutting the grass, no resistance at all when using it. It is a pull start type. I will look at the filter and get someone more knowledgeable than I to look at the plug!.

[Chipchopper]

Could be sediment building up in the float bowl.

[JB86London]

You may have a perished pipe from the bottom of the tank leading to the carb maybe a small split or something in it there is probably no sign of a puddle of fuel as it evaporates quite quickly also check the nut under the carb is tight

[percyveer]

Thanks again for the latest advice. I am as far removed from a 'petrol head' as it is possible to imagine. but I will investigate to the best of my limited talents!

[Clanad]

You may wish to (or have someone do it for you) check the security of the bolt on carburetor. Thing is (it's probably held on to the engine by 4 bolts) if it's loose, the engine will still often work, but drawing excessive air, it will draw excessive fuel as well.

There will be staining at the base of the carb where fuel is leaking out, but not much else will be telling, except, perhaps, dieseling, which is the engine continuing to run (roughly) after shutting it off by usual means. This is caused by the engine continuing to draw fuel/air mixture even though the shut-off mechanism is turned "off"...

[TWR]

Possible Fuel pipe Porous under the tank that can not be in your view.

[EDDIE51]

What engine is it ? Most mowers of whatever make have Briggs and Stratton motors. They are very reliable but do need a service now and again just as a car engine does.

[EDDIE51]

Briggs and Stratton service guide here
http://www.briggsandstratton.com/us/en/support/faqs/engine-problem-solving-tips

[percyveer]

Good morning folks. Thanks again for the advice and suggestions. I'm going to get the manual out and have a look at the bits I can see - without tampering with things which I do not understand! Then its off to the repair man I guess. Ta again everybody.