SPRING PETROL ENGINE PROBLEMS

The sun has been shining a bit this last week and I’ve noticed some people starting to think about mowing their lawns again. If you’ve got a petrol mower in the shed, or anything else with a petrol engine, then read on for some tips on waking it up after winter.

Assuming your engine has been stored in a reasonably dry place you could be forgiven for thinking it should just start up, just like it did last year. However this often isn’t the case, so here are a few tips for things to try if it doesn’t go.

1. Is there fuel in it?

Yes, it may be a silly question, but it’s very easy for petrol to leak or evaporate over the winter. Make sure there is plenty of fuel in the tank, not just a drop in the bottom. The fuel pick up pipe might not go right to the bottom of the tank.

2. Is the fuel fresh?

This is something lots of people don’t know about and it even caught me out a few years ago with an old Landrover. What they don’t tell you is that modern petrol (it doesn’t happen with diesel) has a very short shelf life. It loses it’s ability to combust easily after only a few months, so that can of petrol you bought last October is unlikely to work in an engine in March. Don’t throw stale petrol away though. You should be able to mix it 1 part stale petrol to 3 parts fresh petrol so you can use it up.

3. Check the spark plug.

Most problems with petrol engines are down to the ignition system somewhere along the line. Older engines may have a magneto ignition system providing the spark to the plug. These magnetos include a coil of very fine copper wire which can rot and short out if kept in a damp atmosphere. Lots of old engine enthusiasts, including classic bikers, take the mag off their machines after the summer season and store it in the airing cupboard over winter!

The easy way to check for a spark is to take the plug out of the engine without disconnecting the plug lead (you might need a special plug spanner for this) and lay the plug on a metal part of the engine. Next try to start the engine while looking at the end of the plug. Is there a spark? It should be a good bright spark. If it’s dim, or not there at all, then you either have a problem with the plug or further up the ignition system. If you now undo the plug lead and put the plug aside you can now use something well insulated to hold the end of the lead very close (about the thickness of a credit card) to the metal engine block and try starting again. You should see a spark jump from the end of the plug lead to the engine block. If the spark is now ok you know it was the plug at fault. Get a new plug and you should be ok. If however you still don’t see a spark then the problem is elsewhere in your ignition system and may need some replacement parts. At this stage it’s best to get an expert to take a look at the ignition system.

Remember to check the oil!

If your engine is a 4-stroke machine it will have a sump full of engine oil, just like a car. If it’s 2-stroke then the lubricating oil is mixed with the fuel and generally won’t have an engine oil sump.

The oil should be at the correct level in 4-stroke machines and should also be checked for signs of water, which will normally show up as a light brown sludge on the dip stick. Condensation can form on the inside of an engine block if it is left standing over winter in an environment such as an unheated shed. This then runs down and mixes with the oil, forming the ‘chocolate milkshake’ and making the oil useless. If you see any signs that water may have mixed with the oil then drain and change the oil immediately. Never attempt to start an engine with contaminated oil. It won’t lubricate things properly and you could find a new engine or a costly rebuild will result.

Finally, remember you can always bring you trusty mower etc over to our Repair Cafe events for a check over. Even if it’s not broken, bring it along if you’re not sure what to do and we’ll be happy to check it for you.

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