Autopapyrus · UAZ Patriot 2.2 Diesel ZMZ-51432 (2014)
https://autopapyrus.com/guides/uaz/patriot/diagnosing-the-high-pressure-pump-and-fuel-system-no-fuel-in-the-high-pressure/
https://autopapyrus.com/guides/uaz/patriot/diagnosing-the-high-pressure-pump-and-fuel-system-no-fuel-in-the-high-pressure/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.
UAZ Patriot 2.2 Diesel ZMZ-51432 (2014): Diagnosing the High-Pressure Pump and Fuel System, No Fuel in the High-Pressure Lines
The ZMZ-51432 is a Common Rail Euro 4 diesel with a Bosch high-pressure pump. You can't judge fuel delivery by eye by loosening the lines here: the rail builds pressure only while the engine is cranked by the starter, and the pump's supply depends on low-pressure fuel and on the control valves. A lack of fuel in the high-pressure lines is most often caused by problems on the low-pressure side (filter, air, lift pump), not by the high-pressure pump itself.
Parts
4| № | Part |
|---|---|
| 01 | Fine fuel filter with water sensor |
| 02 | Low-pressure lift pumpif faulty |
| 03 | Pressure control valve or metering valve, high-pressure pumpif faulty |
| 04 | Bosch high-pressure pump, completeif faulty |
Tools
8- Scan tool with support for Common Rail diesel systems
- 10/12/14/17 mm wrenches
- screwdriver set
- clear hose
- container for fuel
- clean rags
- multimeter
- low-pressure gauge with adapters
Step by step
12 steps- Check the obvious first: the fuel level in the tank (with a low level on a slope, the pump draws in air), the diesel quality, whether the fuel has gelled in cold weather, and whether there is water in the filter. If the filter was changed recently, hoses were removed, or the tank ran dry, air in the system is the most likely cause.
- Shut off the engine and let it cool down. Disconnect the negative battery terminal before doing any work on the high-pressure lines. Do not open high-pressure connections on a running engine or right after shutdown. Rail pressure can be very high, and the spray can penetrate skin.
- Connect the scan tool and read the fault codes. Pay attention to codes for the rail pressure sensor, the metering valve, the crankshaft speed and camshaft position sensors, and the pump power supply circuit. Write down the codes and the live data: rail pressure should rise while the engine is cranked. If it barely rises during cranking (below the start threshold, usually a few hundred bar), fuel will not reach the lines and the engine will not start.
- Check the low-pressure fuel side: inspect the fuel filter, drain the water from the filter through the drain valve, and check the supply hoses for cracks and air leaks. For diagnosis, temporarily replace a section of the supply hose with a clear one. Air bubbles during cranking point to an air leak or a weak lift pump.
- Check the lift pump operation: when the ignition is switched on, the electric pump (if fitted) usually runs briefly and you can hear a hum. If you can't hear the pump, check the fuel pump fuse and relay, the power at the connector, and the ground.
- Measure the low-pressure fuel supply pressure at the high-pressure pump inlet with a gauge while cranking. Specific values for the ZMZ-51432 are not clearly documented in public sources, so follow the general principle: the pressure should be stable, without drops or pulsation caused by air. For Common Rail systems, low-pressure supply is usually around 0.5-6 bar, depending on the design. If there is no pressure or it is unstable, replace the filter and check the lift pump and the fuel line.
- Replace the fuel filter if it hasn't been changed in a long time or if it contains water or dirt. Fill the filter housing with clean fuel if the design allows it, then bleed the system with the hand primer (if fitted), or cycle the ignition on several times and crank the engine in short bursts of 10-15 seconds with 30-60 second pauses.
- If the air is bled and the low-side pressure is normal, but the scan tool shows that rail pressure still isn't rising, check the pressure control valve or the metering valve of the high-pressure pump. There should be a control signal at the connector. Compare the coil resistance with the typical Bosch value (usually a few ohms). A valve stuck open dumps fuel into the return line, and the pressure does not build.
- Check the return line: if a strong stream of fuel flows from the return line while cranking and the rail pressure does not rise, this points to a faulty pressure regulator, possibly with leakage through the injectors. Checking injector return volumes requires special equipment and graduated test tubes, and is done at a specialized diesel shop.
- Only after ruling out the low-pressure side, the valves and the electrical system can you suspect wear of the high-pressure pump itself (mechanical damage, plunger wear, a broken drive). Signs: metal shavings in the filter, heavy wear noted when cranking, very low delivery with normal valves. Repair and replacement of a Common Rail high-pressure pump are done only at a specialized diesel injection shop, followed by adaptation.
- To check the high-pressure lines: do not unscrew the fittings at the injectors and the rail "to check delivery" unless necessary. If a check is still required, do it briefly while cranking, wearing safety glasses and gloves, with the connection covered with a rag. Tighten high-pressure line fittings with a torque wrench, using the value specified by the engine manufacturer (usually around 20-30 N·m (15-22 lb-ft) for fittings of this type). Bending and reusing severely deformed lines is not acceptable.
- After fixing the cause, clear the codes with the scan tool, start the engine, let it idle for 3-5 minutes, and check for fuel leaks and new fault codes.
Common mistakes and warnings
- A Common Rail system operates at pressures of hundreds of bar or more
- Do not loosen fuel connections on a running or just-stopped engine, and never check delivery with your fingers or hands
- Do not run the ZMZ-51432 on contaminated fuel, because water and dirt quickly destroy the pump and injectors
- If you have no experience with high-pressure diesel systems, or the diagnostics did not reveal the cause, take the vehicle to a diesel injection repair shop