GEAR 4W6676 - Caterpillar

too much fuel or not enough fuel for combustion can be the cause of a problem in the fuel system. Work is often done on the fuel system when the problem is really with some other part of the engine. Finding the cause of the problem can be difficult, especially when smoke comes from the exhaust. Smoke that comes from the exhaust can be caused by a faulty fuel injector. Smoke can also be caused by one or more of the reasons that follow:
Not enough air for good combustion
An overload at high altitudes (if applicable)
Oil leakage into combustion chamber
Air inlet and exhaust leaks
Not enough compression