Why Does My Carburetor Backfire?by Lissabeth Ross
A carburetor backfire describes the small explosion that sometimes occurs when starting up a car. It generally makes a loud sound, like a gunshot, and occasionally is accompanied by a visible flame.
What Causes a Backfire
Generally, a backfire is caused by an imbalance in the air to fuel ratio. Either the engine is not getting enough fuel, which is also called running lean, or the engine is getting too much fuel, which is also called running rich. There are a few different issues that can create this situation.
If your engine is not timed correctly, it may backfire. If your car has an ignition distributor, adjusting it may be able to correct a timing issue. Otherwise, the timing of the engine will need to be adjusted with a timing light.
Fuel Pump and Fuel Filter
A faulty fuel pump, or a clogged fuel filter, is another possible cause of a backfire. Your fuel filter should be changed regularly. A faulty fuel pump is a much bigger issue. If your fuel pump is failing, it will need to be replaced immediately.
Fuel Injection System
If your vehicle is equipped with a fuel injection system, make sure that it is cleaned and maintained regularly. A clogged fuel injection system will not burn fuel completely and can cause backfires.
A leak in the injection system, usually the result of a stuck air intake valve, is another common source of backfires. Using fuel injector cleaner might take care of the problem. If not, you will need to replace the faulty injector.