Fuel Delivery Parameters

FUEL DELIVERY PARAMETERS

NOTE:
These parameters indicate output commands from the logic module to fuel delivery control devices.


FUEL INJECTORS

INJ(mS) - XX.X
INJ1(mS) - XX.X RANGE: 0 TO 99.9 mS
INJ2(mS) - XX.X

For earlier fuel-injected vehicles, the scanner displays the injection pulse width in milliseconds as lNJ(mS) XX.X. The pulse width is the length of time that the logic module commands the fuel injectors to turn on. This analog parameter is displayed for throttle-body and port injection systems.

A high pulse width indicates more on-time and a richer mixture. A low pulse width indicates less on-time and a leaner mixture. There are no definite specifications for injector pulse width, but the reading should change as engine speed and load change. Typical readings range from 1 to 4 mS at idle, up to about 12 mS at wide open throttle (a little higher for some engines).

The throttle-body injection systems on 1988 and later V-6 and V-8 truck engines have two injectors. The logic module sends separate pulse width commands to each injector, and the scanner displays them as lNJl(mS) and INJ2(mS).


ADAPTIVE FUEL ADJUSTMENT

ADDED FUEL(uS) - XXX RANGE: -1024 to +1016 uS

On 1989 and later vehicles, ADDED FUEL(uS) indicates the adaptive adjustment made by the logic module to fuel injector pulse width at idle. A negative number means that the logic module is decreasing the pulse width from its programmed value. A positive number means that the logic module is increasing the pulse width from its programmed value.

This parameter is displayed in microseconds (uS), or 1/1000-millisecond increments. A microsecond equals 0.000001 second.


PERCENTAGE OF THE ADAPTIVE ADJUSTMENT

RANGE: ±25% ON ALL AUTO EFI
FUEL(%) - XXX
RANGE: ±50% ON TRUCK EFI


On 1989 and later vehicles, FUEL(%) indicates the percentage of the adaptive adjustment made by the logic module to fuel injector pulse width at idle. A negative percentage means that the logic module is decreasing the pulse width from its programmed value. A positive percentage means that the logic module is increasing the pulse width from its programmed value.

For 1989 and later vehicles, FUEL(%) is shown at the right side of the top line in the scanner display, in place of injector pulse width in milliseconds.


FUEL SYNCHRONIZING PULSE

FUEL SYNC - XXXX RANGE: OPEN - CLOSED

This discrete parameter on 1989 and later turbocharged engines is a synchronizing pulse from the ignition system that the logic module uses as one of the input signals to control fuel injector timing. With the engine running, FUEL SYNC should be switching steadily between OPEN and CLAST.