Why Does My Carburetor Backfire? Fuel Pump and Fuel Filter A faulty fuel pump, or a clogged fuel filter, is another possible cause of a backfire. Fuel Injection System If your vehicle is equipped with a fuel injection system, make sure that it is cleaned and maintained regularly. Stuck Valve A leak in the injection system, usually the result of a stuck air intake valve, is another common source of backfires.
This is because cylinder pressure is much higher at wide open throttle than at midrange. The lower the cylinder pressure is, the more time it takes to complete the combustion process. You should always use the correct thermostat for your engine.
Without a thermostat the engine would have no way of regulating the minimum heat range. The bottom line is that the manufacturer designed our engines to run with them installed.
You can check the function of your thermostat a number of ways. One method is by letting the engine come up to operating temperature while feeling the upper radiator hose, once the thermostat starts to open, you should feel the hose start to take pressure and get hot.
You can also use an infrared heat gun on the thermostat housing to observe the temperature change as the engine warms up. Some may even remove the thermostat and check its function in a pot of hot water with a cooking thermometer. If a water pump is leaking it almost always means the pump has failed and needs replaced. Before you install a new pump, always check to make sure the impeller spins freely and has minimal end play. Every internal combustion engine runs on a mixture of 14 to 1 which is fourteen parts air to one part fuel.
Proper fuel pressure is needed to atomize the fuel correctly when it leaves the fuel injector to complete the burn process. The most common cause for this problem is a weak fuel pump which cannot supply the volume of fuel needed for the injectors to produce a proper spray pattern or deliver the amount of fuel needed for engine acceleration.
The fuel system pressure must be tested to see if the fuel delivery system is the problem. Some cars have a fuel filter which can also cause a fuel pressure and volume restriction. When they plug due to particles in the gasoline they can case a lean condition. If you have not changed the fuel filter lately locate and replace it. Your vehicle's computer system monitors the air that enters the engine via the mass air flow sensor. When this sensor malfunctions due to a condition called coking the hot wire inside the sensor becomes contaminated and will alter the reading to the computer which will create a lean mixture condition that may or may not trigger a check engine light.
The lean condition is because the computer thinks there is less air entering the engine than there actually is, less air means less fuel. The first step is to remove the MAF sensor and clean it using carburetor cleaner. We have had better luck by replacing the sensor because once this condition happens the hot wire can become unresponsive in which case the sensor needs to be replaced. The air intake boot or tube transfers air from the mass air flow sensor into the throttle actuator and then into the engine.
If there is a problem with these parts such as a tear or rip it will allow un-metered air into the engine which the computer will see via the oxygen sensor which in turn will deliver less fuel creating a lean condition. Check this part for damage by removing it for inspection and replace it if needed. The engine's intake system depends on being completely sealed and free from leaks. The general rule of thumb is to tighten the adjustment screw s into the carburetor with a screwdriver while the engine is idling until the engine speed starts to increase, then loosen the screw s half a turn.
The fuel tank should therefore be drained if the fuel has been standing for more than three months. If the backfiring only occurs when the engine is cold, makes sure the carburetor's choke is not stuck in the open position. Of course, for some reason, almost everyone calls that a "backfire", probably because the word itself sounds better.
Dan Thomas , Apr 22, Dan- thanks much- I read about clearing the carb of ice as you described on other threads and you explained how it works very well. Cap'n Jack , Apr 22, You must log in or sign up to reply here. Show Ignored Content.
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