Eight Phenomena of High Pressure Common Rail Faults

Eight Phenomena of Common Faults for High Pressure Common Rail:

I. Gear pump doesn’t outlet oil when fuel system need rule out the air again for electronically controlled high pressure common rail diesel engine.

Troubleshooting Methods:

1. Gear pump doesn’t work without fuel. Thus we have to add some guide oil to pump which will be lubricated and sealing, and then the gear pump can work. (Just like adding guide oil to assemble engine gear type’s pump).

2. Exhaust the air of fuel feeding system in order.

3. Oil return pipe of high pressure common rail sinks in the bottom of tank (the same to the inlet oil tube), so the air in the oil return pipe should be exhausted clearly.

4. Ensure enough inner diameter of oil tube (generally 2mm to 3mm bigger than the diameter of oil tube of Standard Two engines).

5. It begins to supply fuel for plunger components of high pressure pump by normal rail pressure controller when gear fuel pump is sealed. After reaching specified valve, rail pressure returns oil through low pressure return oil valve between oil tube and tank.

6. As long as the plunger gets the oil supplied by gear fuel pump. The air in high pressure rail system is exhausted automatically through injector and rail pressure limiting pressure valve. So do the standard two engines. Some repair staff open starter at the first time after assembling the engine in order to start ASAP. The 6 pieces of nipples of high oil pressure will be loosen after high pressure oil tube come to oil, and then tighten the high pressure tube again. The engine can be started successfully at the second try. It’s a faster way to exhaust the air in the high pressure tube.

7. As long as the electronically controlled injector and rail pressure limiting pressure valve is good, the pressure of high pressure rail will not drop down. The engine can start next time no matter how long it stops.

 

II. The two pieces of high pressure outlet tube don’t drain oil. Rail pressure cannot be built up in this situation. If the measurement unit is fine, low pressure parts have problems. Gear pump’s fuel cannot enter into high pressure pump. 

 

III. A new pump was changed. It can drain oil, whose highest rotating speed can reach 2300. However, it stalled after operating long time at a rotating speed of 1500. What caused this problem? Did the oil block the filter and the oil pressure couldn’t be built?

We found it’s the problem of oil way, especially when filter is serious blocked. In summary, the pressure of inlet and outlet oil cannot reach requirements.

    

IV. Engine cannot speed up any more at 1500 turn. 1500 turn is a kind of failure mode of engine and protects the engine. Too high water temperature and too low oil pressure also belongs to this kind of protection.

The Engine cannot speed up due to insufficient rail pressure. The reasons may come from: low pressure oil, common rail relief pressure valve, measurement unit or high pressure pump.

 

V. How does traffic volume valve work? Does it control oil pressure fluctuation and pressure of common rail tube? 

Traffic volume valve is the same to the injector and the actuator of common rail. It’s integrated installed in the high pressure oil pump. Accurate control will be did in real-time for oil of common rail pipe and realize the adjustment of fuel pressure from high pressure pump.

 

VI. The oil amount is too small through the fuel measurement unit for a shortage of low pressure oil. The result is that rail pressure is not enough and engine has no power.

 

VII. How does the computer sense that the oil amount is too small flow through fuel measurement unit? In other words, how does the computer measure the oil amount of flowing through the fuel measurement unit?

 

VIII. Fuel measurement unit is actuator, the same to injector. It is not responsible for measuring oil amount and only controlled by the computer.

If the rail pressure is not enough, the computer will know the oil amount through fuel measurement unit is too small.

If the oil amount pump from injector is bigger than the oil amount of fuel measurement unit, the computer will also know the oil amount is too small.

The above both benefit from the rail pressure sensor.