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Fuel Accuracy Troubleshooting Guide

Technical Service Bulletin
Technical Service Bulletin: TSB200115
Fuel Accuracy Troubleshooting Guide

Released Date: 25-Jun-2020

Fuel Accuracy Troubleshooting Guide
Warranty Statement
The information in this document has no effect on present warranty coverage or repair practices,
nor does it authorize TRP or Campaign actions.

Contents
Product Affected
ISX15 CM2250 SN
Issue
This TSB provides instructions to detect the root cause of fuel consumption accuracy issues
reported by customers. When comparing fuel consumption values in INSITE™ electronic service
tool to customer measurements (vehicle mileage divided by liters of fuel filled) the results differ by
more than +/- 3 percent. The root cause determined by investigations is inaccuracy in
measurement performed by the end user.
Verification
Step 1: Gather and review value and calculation method provided by the end used.
Fuel Accuracy = ((Fuel filled - Fuel reported by ECM) / Fuel filled) x 100
Review and confirm method used by end user to calculate fuel accuracy.
If average value from fleet is out of the specified by Cummins® (+/-3%), continue to step 2.
If average value from fleet is under values specified by Cummins® (+/-3%), notify the end
used that value meets Cummins® specified values.
Step 2: Review end user fuel consumption information.
Fuel consumption data (real measurement vs ECM reported)
Operator names for each trip performed
Customer routes
Gross Combined Weight (GCW)
Kilometers from unit odometer
Number of affected units
Truck model affected
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Does the end user have self-consumption?
With the information gathered, most critical units will be defined.
Step 3: Review measurement method according to Fuel Consumption Test Procedure
es175-005-010-tr.
Confirm that powertrain coincides with information provided by end user.
Confirm that fuel supply pumps used by end user are certified.
Review general connections of fuel system to discard leakages or external factors.
Review customer method to calculate the fuel supply pump correction factor.
Step 4: Review maintenance information related to engine.
Review the fuel system:
Correct primary fuel filter (Filter capacity 7-10 micron and WIF included). Check Owner's
Manual for correct fuel filter part numbers.
If maintenance schedule information is available, review primary fuel filter purge and change
interval information.
If units meet the Cummins® maintenance recommendations, perform a physical test to measure
fuel accuracy with the units that are most out of the expected fuel accuracy value.
Step 5: Perform fuel consumption test.
Once steps 1 through 4 are completed, perform fuel consumption test to measure and confirm the
engine fuel consumption accuracy. After the test it is required to complete a report that describes
the test conditions, observations, and vehicle profile.
Before the test, record information below from unit:
OEM:
VIN:
ENGINE:
ESN:
HP:
GEAR:
TIRE/DIAMETER:
KM ODOMETER:
Gross Combined Weight (GCW):
ROUTE:
Before the test, review and record the condition of the following:
Air filter
Fuel filters
Fuel lines
Fault codes
Before the test, it is also recommended to review and record the condition of the following if
possible to ensure the safety and performance of the vehicle and to prevent test interruption:
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Oil level
Coolant level
Vehicle shock absorber
Tire pressure
If an issue or leak is detected on the unit, or the operator is not able to perform the test, the test
will not be performed until issues are resolved. It is expected to have ideal conditions for the test
with competent operators.
Fill and mark the fuel tank(s) to 95% full during initial fill. It is recommended to use ¼ inch hose to
confirm the fuel tank is 95% full. Mark the level on the hose. See Figure 1.
The audit jar must be used during initial fill to calculate the fuel supply correction factor. See
Figure 2.
Initiall fill: Refers to filling the fuel tank at the start of the test. The fuel tank must be at 95% of
the fuel tank capacity. Filling more than 95% capacity could lead to expansion of fuel from fuel
temperature and can cause fuel spillage and leakage.
Download and reset trip information.
For the final fill (and intermediate fills if applicable), calculate the fuel supply correction factor with
the audit jar. See Figure 2.
Final fill: Is the refilling of the fuel tank after finishing fuel consumption test. The fuel tank must
be filled to 95% capacity and fuel must be cold. Performing the final fill with high fuel
temperature could cause a volume decrease when the temperature decreases.
Audit Jar Instructions:
Audit Jar: Use the audit jar to audit the fuel supply pump to ensure that the volume filled in the
tank will be accurate versus the volume calculated on the ECM. The audit must be performed
during the initial fill and if the final fill is performed in another fuel supply pump, that pump
must be audited to know the fuel pump correction factor.
Example:
Program the fuel supply pump and fill the audit jar, the volume showed on the
display is know as "Vb", volume supplied by pump, and the volume registered on
the audit jar is know as "Vr" real volume showed on the audit jar.
Calculation is made next:
FCB= Fuel pump factor correction
FCB = Vr/Vb
Example:
Vr=19.850
Vb=20
FCB= 19.850/20 = 0.992
From using the audit jar and performing the fuel pump correction factor calculation,
the supply pump fill relation is not a one-to-one relationship. Filling a truck with 500
liters of fuel and applying the correction factor (500x0.992) results in 496 liters; a
difference of 4 liters is caused by fuel supply pump calibration.
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Resolution
Share the test results and recommendations with the end user.
If confirmed that the customer's measurement is accurate and correct, adjust the parameter Fuel
usage factor using INSITE™ electronic service tool. Fuel usage factor is an adjustable parameter
(+/- 5%) from the nominal 100%.
Based on the results after the test of fuel consumption accuracy, if value is out of specification
(+/-3%), based on affected units fuel consumption average, enter “fuel usage adjustment” with
value calculated.

Note : Fuel usage factor is an editable parameter (+/-5%) from the nominal 100%.
Cummins Inc. is not responsible for how external users use this feature.
Steps for adjusting Fuel usage factor with INSITE™ electronic service tool. See Figure 3.
1.
2.
3.
4.

Connect with electronic service tool
Go to Features and Parameters
Enter calculated value
Make sure the change is properly made.

Appendix

Figure 1, 1/4 Hose To Confirm Fuel Level

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Figure 2, Audit Jar And Scale For Checking Fuel Supply Pump

Figure 3, Adjust Fuel Usage Factor

Document History
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Fuel Accuracy Troubleshooting Guide

Date
2020-5-13

Details
Module Created

Last Modified: 25-Jun-2020

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