Detecting a

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Detecting a Lean Injector...
How it works...
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This illustration represents the air-fuel mixture
inhaled by each cylinder of a typical 6-cylinder
engine. The fuel injectors are specifically
designed to match the air displacement with the
precise amount of fuel for optimum performance.
Residual AIR
FUEL MIXTURE
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In order to meter the AIR-FUEL-RATIO precisely
, a small amount of residual air generates
enough oxygen to toggle the O2 sensor between
lean and rich for the most economical fuel
consumption.
How it works!
Residual AIR
FUEL MIXTURE
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Reduced fuel flow due to a restricted inlet
screen.
THE FUEL INJECTOR
This marvel of modern ingenuity is subject to
failure due to no fault of its own!
Sluggish plunger movement due to contamination.
There are several excellent ways to check
electrical functions
Improper seating of the pintle valve due to dirt
particles.
However no easy way to test mechanical failures
like
Deposits on the nozzle affecting the spray
pattern.
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If all injectors are equally contaminated, the
injector on-time would increase, but the fuel
volume remains the same resulting in no change of
AIR-FUEL-RATIO. The FUEL TRIM may indicate a
higher reading but there is no significant
detrimental effect to the engine.
Residual AIR
FUEL MIXTURE
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However, with only one injector restricted, fuel
distribution per cylinder is uneven and the
computer compensates for the leanest injector.
RESIDUAL AIR
FUEL MIXTURE
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Since all the required oxygen to make the O2
sensor function now comes from one cylinder, the
computer drives the other cylinders rich. Over
time, this results in carbon deposits on valve
stems, O2 sensor, EGR valve, converter, etc.
FUEL MIXTURE
To identify which is the lean injector, we trick
the computer in subtracting fuel until this
injector misfires.
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Pushing this button artificially adds small
increments of fuel
to one of the injectors.
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1
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This will drive the computer to take more fuel
away, and this lean cylinder is affected most.
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When continuing to add more fuel
this cylinder eventually misfires.
FUEL MIXTURE
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By consulting the scanner we can tell which
injector is the faulty one!
When this cylinder misfires we know that we
diagnosed the problem.
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Reading the fuel trim data, the scanner can
indicate a potential problem but cannot
pin-point the source. It is important to know!
The Fuel Trim Generator is the easiest way to
detect the restricted injector. In addition, this
method also identifies the number of lean
injectors and whether or not it is a problem.
Since the computer compensated with a richer fuel
mixture, a restricted injector may cause long
term carbon damage to engine and delicate
components.
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For full description download this PowerPoint
presentation
CLICK THERE TO LINK TO THE VIDEO SECTION
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For full description download this PowerPoint
presentation
CLICK THERE TO LINK TO THE VIDEO SECTION
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