Diagnosing a no-start condition due to failure of the Fuel Pump involves systematic testing of the fuel delivery system to find the root cause. No-start conditions include when the engine cranks but does not fire because of a lack of sufficient fuel, which often points toward the Fuel Pump. According to studies conducted by AAA Automotive Services, about 15% of no-start conditions in vehicles are related to problems with the fuel pump.
First step in diagnosis is to listen for the Fuel Pump priming sound when the key is turned to the “on” position. Normally, the pump will make a low humming noise for 2-3 seconds while it pressurizes the fuel system. If no noise is heard, there is a possibility the Fuel Pump is not getting power or has failed. To confirm this, one needs to check the fuel pump relay and fuse since 20% of pump failures are electrical according to the National Institute for Automotive Service Excellence-ASE.
Using a fuel pressure gauge is the next step in confirming if the Fuel Pump is delivering adequate pressure. Most vehicles require fuel pressure between 35-70 psi depending on the engine type. Hook it up to the fuel rail, switch on the ignition, and take the reading. If it’s lower than the manufacturer’s recommendations, it means the pump is either weak or clogged. A bad Fuel Pump usually cannot produce more than less than 10 psi, hence not able to fire up the engine.
It’s time for checking the flow of fuel. Disconnect the fuel line feeding the injectors and route it into a container. Then, turn the key to the “on” position. If no delivery of fuel occurs, this confirms a blockage or complete failure of the pump. A clogged fuel filter can also restrict flow and force the pump to work harder until it fails. If the pump itself is intact, a clogged filter would require replacement costing about $30-$50, which could restore it to operation.
Electrical testing will show if the power is reaching the Fuel Pump. A multimeter will read voltage at the connector of the pump; this should read 12 to 14 volts when the ignition is turned on. If the voltage is not present or fluctuating, then your problem is in the wiring, relay, or ECU. In many cases, repairing one of these electrical problems will be much less expensive than replacing the pump. Relay replacements have an average cost of $15-US$50.
Sometimes, DTCs from an OBD-II scanner give further insight. Codes such as P0087 for low fuel pressure or P0230 for a fault in the primary circuit of the fuel pump point directly to the fuel system and thus confirm the Fuel Pump as the problem area.
Timely diagnostics save both time and money,” confirms John Davis, an automotive expert at Bosch. Early addressing of a failing Fuel Pump will prevent further damage to the engine or fuel injectors that could cost $500-$1,000 in repairs.
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