Even though fuel injectors have been around since the late 1960's, diagnosing injector related problems continue to baffle some technicians even today. A fuel injector is a very simple device consisting of a coil of wire, a spring, and a pintle valve. Each time the ECM activates the injector circuit, magnetism causes the pintle to move against the spring and allow fuel to flow. Throttle body and port fuel injectors both have the same components and operate in the same way with only the pulse time and duration being the only functional difference. Injectors look the same but cannot be interchanged because of coil resistance, spray pattern, and flow rate differences.

An injector with the wrong coil resistance could also cause the symptoms listed above. Injectors must have equal specifications for the engine to perform correctly under all operating conditions.

Some commercial injector cleaners can cause the insulation to be washed off the windings of the injector causing a low resistance condition or a short. The Multec type of injector seems to have a shorter life span than the Bosch style units, with the Multec style developing shorted coil windings very early in it's life. Sometimes an injector with a resistance value that is borderline can go below the minimum acceptance value after being in operation for a short time. A shorted injector can cause ECM damage if the resistance is too low. If the resistance is in doubt, throw it out!

Most of today's gasoline has additives to keep fuel injection systems from forming deposits and clogging but fuel contamination and high mileage can cause injector blockage. Many different problems can occur when injectors start to leak or become partially or completely blocked. Some of the symptoms could be:

Rough idle

No start condition

Hard cold starting
 
Flooding on hot start
 
Rich fuel mixture
 
Fuel leaking onto engine

Poor gas mileage