HGV fuel pump replacement: low pressure versus high pressure
HGV fuel systems use two distinct pump types that work in series. The feed pump draws fuel from the tank at low pressure and supplies it to the high-pressure pump. The high-pressure pump generates the injection pressure required for the injectors. Both can fail, but they fail in different ways and require different diagnostic approaches.
A failing feed pump shows as fuel starvation: hard starting, power loss at high loads, and rough running. A failing high-pressure pump typically causes hard starting in all conditions, excessive smoke, misfires, and poor power across the load range. Never replace the high-pressure pump without first confirming feed pump supply pressure meets specification.
Frequently Asked Questions
How do I tell if the fault is in the feed pump or the high-pressure pump?
Test feed pressure at the pump outlet first. A reading below the manufacturer's specified value points to the feed pump. If feed pressure is correct and the fault persists, connect a rail pressure gauge or use a diagnostic scan to check actual versus target rail pressure, which points to the high-pressure pump.
Does the fuel filter need replacing when a fuel pump is replaced?
Yes. A blocked or contaminated filter causes the condition that leads to premature pump wear. Always replace the fuel filter at the same time as any fuel pump replacement.
Can contaminated fuel damage a high-pressure injection pump?
Yes. Diesel contaminated with water, petrol, or particulates can score the precision-machined bores inside a high-pressure pump within hours of operation. Check the fuel supply for contamination before fitting a replacement pump.
Does Truckstop Group stock fuel pumps for all HGV makes?
We stock fuel pumps for the main HGV makes including DAF, Scania, Volvo, MAN, Mercedes-Benz, Iveco, and Renault. Call us on 01527 598 000 with your chassis number and fault description to confirm the right part for your application.
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