Fuel Pressure Test Kit – Low-Pressure / Pre-Supply Systems for Diesel / Common-Rail Engines

This fuel pressure test kit allows mechanics to measure the pre-supply or low-pressure fuel system on most diesel engines. Deviations in the low-pressure side often lead to downstream high-pressure failures that are not always recorded in fault memory.

The kit supports both analog and sensor-independent evaluation as well as real-time value checks, allowing a reliable inspection of multiple components, including:

• Pre-supply fuel pump

• High-pressure fuel pump

• In-tank pump

• Leaking lines

• Faulty check valves

• Defective injectors

Usage – Step by Step

1. Checking Pre-Supply or In-Tank Pump Pressure

• Begin measurement at the fuel filter inlet. Record the displayed pressure.

• This checks the actual pre-supply pressure. During engine operation, the pressure should remain almost stable, independent of RPM.

2. Fuel Filter Flow Check

• Low flow due to blockage or fuel degradation is common.

• First, measure at the filter inlet. If plausible, repeat the measurement at the filter outlet.

• Compare values to identify restricted flow through the filter.

3. Checking for Backflow through Defective Check Valves or Leaks

• Leave the gauge connected to the supply line after engine shutdown.

• If a vacuum is observed before the check valve, the valve is faulty, allowing fuel to return to the tank.

• Particularly noticeable during long engine start attempts.

System Compatibility

• Suitable for many low-pressure fuel systems with 7.89 mm connections (standard in ~90% of vehicles).

• For wider vehicle coverage, we recommend using adapter hose set Art.-Nr. 117010 – Fuel System Venting Tool Set, 10 pcs.

Set Contents

• 1 × Coil spring pressure gauge, range –1–1.5 bar, with quick connector

• 1 × Coil spring pressure gauge, range 0–16 bar

• 1 × T-piece adapter with quick coupling for gauge and Ø7.89 mm female line connector

• 1 × Connection / adapter hose Ø7.89 mm male/male