Various methods for diagnosing diesel fuel pump failures pinpoint the problem area of the fuel system. Diesel engines require a very accurate dole of fuel to run smoothly, and failure in the fuel pump will result in severe performance issues. One of the major areas to consider is fuel pressure. Diesel engines rely on high levels of pressure to inject the fuel into the cylinders effectively. For example, most normal diesel fuel pumps operate on approximately 4,000 to 6,000 psi of pressure, which varies based on the type of engine. If the pressure drops, this is a sure sign that the fuel pump may be failing.
The first general step in testing for a failed fuel pump is measuring the fuel pressure with a fuel pressure gauge. If the gauge shows a reading below the scale set by the manufacturer, this means that the pump is not producing enough pressure. Often, this may be due to wear and tear on the fuel pump components, which commonly happens over time. As a matter of fact, the general life expectancy of fuel pumps in diesel engines is up to 150,000 to 200,000 miles, though they easily can fail prematurely due to poor fuel quality or failure to service them. According to the National Institute for Automotive Service Excellence (ASE), fuel pump failure accounts for approximately 8% of all diesel engine failures.
Another way to diagnose a fuel pump in a diesel engine is to check the fuel filter and fuel lines. Contaminated or plugged filters are very common in diesel systems and may require the pump to work much harder, sometimes resulting in failure. Diesel fuel filters have to be changed out periodically for peak performance. According to a study by the Diesel Technology Forum, 25% of all diesel engine fuel pump failures were due to filthy or clogged filters. Thus, the condition of the filter is one of the important steps in diagnosing fuel pump problems.
Also, in addition to inspecting fuel pressure and filter conditions, an absolute necessary task would be an outward inspection of the fuel pump to show potential external signs of damage or leakage. Any seepage through the fuel pump or its feed lines creates conditions leading to loss of fuel pressure with resulting under-power. Fuel leak is one of the main causes of failure of the fuel pumps in diesel engines, representing up to 15% of the cases according to IERI. Leaks showing around the fuel pump or connections could give clear symptoms of malfunctioning.
Also, fuel pump failure might be due to electrical faults. Most diesel engines have an electric fuel pump, which supplies the required pressure for the fuel. Testing the electrical connections of the fuel pump is very important, especially when the engine cranks but does not start. Poor connections or faulty wiring can result in the pump not getting enough power to operate. According to the American Diesel Institute, electrical problems account for approximately 10% of all diesel fuel pump failures.
Diagnosing a problem with the fuel pump usually requires more advanced techniques such as checking the amperage draw of the pump. The fuel pump may be drawing too much current, which could show an internal failure such as worn-out bearings or a bad motor. Using an ammeter, technicians can measure the current draw and compare it to the manufacturer’s specifications. A significant deviation from the normal current draw is an excellent indication of a faulty fuel pump that should be replaced. According to the 2019 report from the ARA, 5% of all fuel pump complaints dealt with excessive current draw.
These methods should be combined with thorough knowledge about the specific requirements of the particular engine when testing for diesel fuel pump failures. Diesel fuel pumps are crucial to the performance and life of an engine, and timely diagnosis can save a lot in repair costs later on. For more information on fuel pump maintenance and replacement, visit Fuel Pump.