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Published on February 6, 2008

If the engine was difficult to start, it didn't run smoothly, or there was a problem with acceleration, a mechanic would simply remove the carburettor and clean it. And the mechanic didn't need a lot of experience to do the job.

These days, nearly all automobiles come with fuel injection instead of a carburettor because injection works more efficiently. The fuel system never floods and there is always enough fuel to ensure plenty of engine power.

The injectors feed exactly the required amount of fuel into the combustion chambers. This is calculated by an electronic control unit that reacts to the throttle position and the amount of air entering the engine. It results in a perfect air/fuel mix and more efficient combustion. Very little unburned fuel comes out with the exhaust gas.

However, fuel injection systems have their downside. They are very expensive to repair, and if you need replacements this will also cost a lot. Specialised tools and mechanics with specific skills are required for the job; it cannot be carried out by a home handyman or a general mechanic. The best you can do is learn how to use the vehicle to prolong the life of the fuel system.

Khun anna_adria e-mailed me concerning problems with fuel injection:

The problem is that the engine doesn't run smoothly at idling speed and sometimes it stalls at a red light. When it does this it takes longer than usual to start, and there's a smell of petrol. The mechanic says it is caused by the flooding, but another mechanic says flooding is impossible in a fuel-injected engine. Nevertheless, neither of them has been able to fix the problem.

Let me guess that the vehicle has a fuel-injected petrol engine, rather than a diesel engine, and it is an early fuel-injected model. If it's a Japanese brand it will have been bought no later than 1995. Cars from the period from 1990 to 1995 are prone to this problem, mostly because of damage to the fuel injectors. Sometimes the problem also involves clogging of fuel lines back to the tank, and this is easy to fix.

Start by checking the fuel line from the engine back to the fuel tank. If the hose is bent or folded, force it back into a normal position so that the fuel flows easily. It may be better to replace the line altogether. If there is a filter somewhere in the line, have it cleaned or replaced.

Next, if you don't want to spend money to adjust the fuel pressure, try using a fuel injection cleaner. A high-quality cleaning agent helps to ensure that the injectors deliver a really fine spray of fuel into the combustion chamber to promote better combustion. The cleaner is simply poured into the fuel tank and the cleaning takes place while the engine is running.

Fuel-injection cleaning agents can be bought at car accessory corners in department stores. I cannot recommend any particular brand, but choose one that has a trustworthy name. The label should also state where it is produced, the contents and any government agency or auto-company approvals.

E-mail your motoring questions to Pattanadesh@nationgroup.com.

By Pattanadesh Asasappakij

The Nation

Ultimate in Luxury

The Luxury LS 460 is a wonderfully comfaortable car fitted with all mod cons, althoough not necessarily the most fun vehicle to drive.