P008APowertrain
Powertrain · SAE
Low Fuel Pressure — Low Pressure Side Too Low
Meaning
Pressure in the low-pressure circuit (supply to the high-pressure pump) is below the minimum required threshold. The ECM detects that the transfer pump is not delivering enough fuel to the high-pressure pump.
Common causes
- Faulty or end-of-life transfer (low-pressure) pump
- Heavily clogged fuel filter causing pressure drop
- Leak in the low-pressure circuit (pipes, fittings, O-rings)
- Fuel tank at too low a level or empty
- Faulty pump check valve
- Obstruction in the fuel suction line
Symptoms
- Check-engine light on
- Hard start or no-start
- Engine stalls when hot or on a slope
- Progressive power loss
- Abnormal fuel pump noise
Severity
High: low-pressure supply deficiency immediately affects the high-pressure circuit; the engine may not start or may stall in motion.
What to do
- Measure low-pressure circuit pressure (typical value: 3–7 bar per manufacturer spec)
- Check fuel level in the tank
- Replace the fuel filter
- Inspect the suction line for obstructions or air leaks
- Test or replace the transfer pump if pressure is consistently low