#Fuel injector oscilloscope pattern code#

Linder says that only a 1 to 3 psi change in fuel pressure can often cause noticeable driveability problems. This can leave the air/fuel mixture too lean, causing the cylinder to misfire.Īccording to Jim Linder of Linder Technical Services (a provider of fuel injection training) in Indianapolis, IN, fuel pressure is probably the most critical factor in the fuel injection system. If an injector becomes clogged with fuel varnish deposits and fails to deliver its normal dose of fuel when it is energized, or fuel pressure to the injector drops below specifications because of a weak fuel pump, plugged fuel filter or leaky fuel pressure regulator, the PCM may not be able to increase injector duration enough to offset the difference. The adaptive fuel control strategies that are built into a PCM that allow it to adjust short term and long term fuel trim to compensate for variances in fuel pressure and fuel delivery can maintain the correct air/fuel ratio - but only within certain limits. Fuel pressure is within a specified range for that engine, and the injectors are all clean and new. The fuel calibration curves in the powertrain control module (PCM) are based on OEM dyno testing using a new engine. Even so, for the engine to run right, fuel pressure to the injectors is critical as is the volume of fuel delivered by each injector when it fires. On older engines where the injectors are all fired simultaneously, the good injectors can often compensate for one or two bad injectors.

#Fuel injector oscilloscope pattern code#

One bad injector will cause a noticeable misfire and usually set a P030X misfire code (where X represents the cylinder that is misfiring). This is especially important on late-model engines with sequential fuel injection. They do, but the question remains, “How much pressure?”įor the engine to start and run smoothly with no stalling, hesitation or misfiring, the injectors have to deliver the proper amount of fuel with every squirt. If the engine cranks but won’t start, and they depress the service valve on the fuel rail and some fuel squirts out, they assume the injectors have pressure. If the engine runs, they assume the injectors are getting adequate fuel pressure.

All too often, technicians assume fuel pressure is “good” without actually measuring it with a gauge.