Petrol Fuel Pump Pressure Check

Does The Pump Run

Key on, ear near the rear seat base. With fuel in the tank the in-tank motor should whir for a few seconds and stop. Continuous run with the key on and the engine dead usually means Limited Operating Strategy: the ECM is in limp and wants a proper diagnostic session, not more guessing at the pump.

No sound at all: check the pump fuse, the relay, and the loom before you condemn the module. Wiring chafe above the rear axle is covered with the sender job in W-462 and in A-088.

Gauge On The Rail

The test point is the Schrader under the plastic cap at the right-hand end of the fuel rail (feed union). Fit Jaguar JD209 or a Schrader-capable fuel gauge. Open the tool tap only after the gauge is on. Start, idle, wait for the reading to settle. Book pressure is 4.5 bar.

• High: look for a pinched return. Clear line still high means renew the regulator where fitted.
• Low: pinch the return briefly. Pressure rises, renew the regulator. No rise, chase feed line, filter and pump.

Where a vacuum hose sits on the regulator, pull it at idle: gauge should climb. Flat response means a bad hose or a dead regulator. Key off, pressure should hold near spec for about five minutes. Crack the gauge off under a rag, mop the spill, run the engine and check for wet joints. Fuel pressure sensor, when disturbed, goes back at 10 Nm.