March 15, 2011
FAILURE ANALYSIS REPORT
Phoenix, Nonoc Island, Surigao City
Engine not starting due to Low Fuel Pressure as reported by CAT ET diagnostics
BH-11 is a 320D Hydraulic Excavator installed with an ACERT Engine, the latest engine design by Caterpillar to meet the Emissions regulations by US Transport. ACERT stands for Advanced Combustion Emissions Reduction Technology; the design is primarily to have an efficient combustion using small amounts of fuel that are injected at precise times to achieve fuel economy and lower emissions.
And in connection to this engine design and efficiency, ACERT's fuel system is sensitive compared to conventional engines. That is why its fuel filtration uses High Efficiency Filters that could remove particles as small as 2 microns.
In addition, ACERT engines are fitted with high pressure fuel pumps and a common rail system with pressures as high as 150MPa (21,755 psi). This pressure is very crucial on our fuel injection system because ACERT uses electronic injectors controlled by the ECM (Electronic Control Module).
During my site visit, I noticed our technicians working on this stalled unit, the mechanic was busy on the fuel system while the electrician was checking the Air inlet system relay. To know what they are doing, I begun to ask questions about the current status of this unit.
Inlet Heater Relay was previously diagnosed to be faulty by the Electrician, so he disassembled the relay and found out that a magnetic wire was cut so he repaired it by soldering the wire and assembled it back and installed to the engine. The coil of this relay was cut due to sudden increase in voltage resulting to an error code of 617-5. The function of this relay is to activate the starting aid system to assist cold engine starting.
I asked the mechanic about what he has done in the fuel system. He said he checked the fuel lines for leaks, perform bleeding, and eventually disassembled the high pressure fuel lines because they assume that a fuel pressure drops after engine cranking.
FLC also told me that most of our equipment had undergone a pressurized washer cleaning which have included the engine compartment.
The following diagnostics and troubleshooting procedures were performed to check the current status of our equipment using CAT ET and Equipment Monitoring System.
- Injector Solenoid Test
- Fuel Pressure Test
- Analog Sensor Test
- Electrical Connector Inspection
Logged Diagnostic Code:
Logged Event Code:
Injector Solenoid Test:
Actual measurements using EMS during Engine Cranking:
- Fuel Pressure = 218 KPa (31.6 psi) / Acceptable reading 25 MPa (3636 psi)
- Fuel Pressure (ABS) = 314 KPa (45.5 psi)
- Battery Voltage = 25.0 VDC
- Batteries are not installed properly; its fixture cover was not clamped.
- Battery cables, clamps & terminals are loose with visible corrosions.
- All compartments are dirty (Battery & Air Cleaner/Radiator/Hydraulic Pump)
- Electrical components are still wet due to pressure washing
- Disconnect switch is corroded/rusty and turning the switch is a bit hard
ANALYSIS AND CONCLUSION
Based on all of the information & data collected herein, it was determined that the failure is a result of the following causes.
- A sudden voltage increase occurred supplying the inlet heater relay which had caused the coil to be cut. This sudden increase may have been caused by a voltage jump on the battery supply.
- Cleaning of engines with pressurized water is not recommended because it may cause short circuit to the electrical system. That is why the battery is easily drained.
- The disconnect switch is not properly maintained. They are using welding rods to twist the switch instead of a disconnect key. Improper contact on contact points among switches may have caused electric arcs thus fluctuation of voltage supply may occur. And this sudden increase in voltage will cause damage to electronic systems especially the ECM.
- The fuel high pressure line was disassembled by our mechanic. ACERT engines are sensitive on its fuel pressure lines. Caterpillar advised that once a high pressure line is disassembled, a new pressure line should be replaced this is because it may have deformed the shape of its fittings or tube ends.
- Replace Inlet heater relay
- Replace fuel high pressure lines (6 pcs.) for all injectors
- Re-evaluate Equipment cleaning procedures especially when using pressure washers and re-orient maintenance personnel
- Batteries should be installed properly on its compartments as prescribed by the manufacturer's specification.
- Proper maintenance of disconnect switches must be practice.
- Cleaning of all compartments must be strictly imposed to the machine operators
- Perform walk-around inspection before and after operation
- Training of mechanics about ACERT Engines is required