4
7 - Fuel System Test – Using Minidiag2
CAUTION
To avoid injury when working near or on an operating engine,
remove loose items of clothing, jewelry, and tie back or contain
long hair that could be caught in any moving part causing injury
CAUTION
Diesel engine exhaust and some of its constituents are known to
the state of California to cause cancer, birth defects, and other
reproductive harm.
o Always start and operate an engine in a well-ventilated
area.
o If operating an engine in an enclosed area, vent the
exhaust to the outside.
o Do not modify or tamper with the exhaust system or
emission control system.
NOTE:
Before running the test, warm the engine to normal operating
temperatures: 176F to 203F (80C to 95C)
a) Idle Smoothly Balance (Fuel Delivery):
This test measures the percentage of fuel contribution for each cylinder in order to maintain a smooth
operation at idle. Operational range for this test: from –3%(negative) to 3% (positive).
Identify the cylinder with biggest absolute value – highest positive or lowest negative. The
troubleshooting steps for both conditions are:
1. For highest positive:
o Step 1: Check torque at all the transfer tubes nut (33 lbf.ft / 45 Nm). Run the test
again. If the results are out of the operational range, proceed to the next step.
o Step 2: Find the cylinder with result closest to zero. Swap the injector nozzle holder
and the transfer tube between this cylinder and the cylinder with highest result. Run
the test again. If the highest result follows the injector nozzle holder, replace it. If not
proceed to the next step.
NOTE: After removing the injector nozzle holders and transfer tubes, please check
the coupling area between both components and the seal rings. If any defect or
damaged is found, replace the damaged parts.
o Step 3: Return both injector nozzle holders and transfer tubes to the original position
and run the impact delay time and compression test routines.
2. For lowest negative:
