Black Smoke

Black smoke is caused by too much fuel being processed inside your car's engine and then released from the tailpipe of your car. Malfunctions in fuel delivery or internal system leaks will cause black smoke to come from the tailpipe. Before fuel injection became available in automobiles in the mid 1980's, the carburetor was the main fuel and air mixer in most vehicles. A carburetor was a simple device that supplied the engine with proper fuel to air mixtures. Carburetors performed two operations 1. meter air flow 2. deliver the correct amount of fuel to air mixture. This mix could be kept even during the wide range of extra factors associated with an engine such as high temperature, cold starting, hot starting, idling and acceleration.

Fuel Injector Cut Away

The primary difference between a carburetor and a fuel injection system is that the fuel injection system atomizes fuel by pushing it through a small nozzle under pressure, while a carburetor utilizes vacuum created by air flow into the intake manifold. Airflow in an injection engine is controlled by the throttle body; fuel is distributed directly in each cylinder. This creates better fuel control, lower emissions and faster acceleration. The process of measuring the amount of fuel a fuel injector is dispersing is determined by the ECM (engine control module). The fuel injection system has several parts: the mass airflow sensor or map sensor, throttle body, throttle position sensor, idle control valve, fuel pump, fuel pressure regulator, fuel lines
, and oxygen sensors.

Cause of Black Smoke
Black smoke is caused when the mix of fuel and air becomes un-balanced. Normal mixture is 14.5 parts air to1 part fuel. When the fuel to air mixtures change because of a malfunction the mixture can go as high as 14.5 to 2 or 3, two to three times the proper amount. The black smoke is the excess fuel generated from the rich mixture and can be cause by one of the following:

* Plugged Air Filter
* Shorted or stuck fuel injector
* Failed fuel pressure regulator
* Vacuum leak
* Shorted ECM Sensor

Trouble Shoot Black Smoke
Check Engine Light
If the check engine light is illuminated the ECM has detected a malfunction that could be causing the problem, scan the ECM to retrieve trouble codes and repair as needed.

Preventive Maintenance
To check your car's mixture you will need to use a gas analyzer to test your exhaust gases. This will measure the carbon monoxide, hydrocarbon, nitrogen oxide and oxygen content of your exhaust. During a normal smog inspection the fuel/air mixture is tested and a report generated. When a tune up is performed the spark plug end insulator can tell you whether you have a lean or rich mixture. Brownish grey is the desired color and confirms proper mixture. Black and sooty means the mixture is too rich while white to light grey confirms a lean mixture.

Fuel injection systems rely on pressurized fuel to operate. Maintaining this pressure is mandatory for the system to function properly. Replace your fuel filter with every tune up to keep your injection system operating properly.