Judgment and Removal of Fail Fuel Pressure in Diesel Engine

Diesel engine fuel pressure will be too low or not pressure due to wear of engine parts, improper assembly or other faults. Faults such as excessive fuel pressure or oscillating pointer of pressure gauge. As a result, accidents occur in the use of construction machinery, resulting in unnecessary losses.

1. Low fuel pressure
When the pressure indicated by the fuel pressure gauge is found to be lower than the normal value (0.15-0.4 MPa), stop the machine immediately. After waiting 3-5 minutes, pull out the fuel gauge to check the quality and quantity of the fuel. If the fuel quantity is insufficient, it should be added. If the fuel viscosity is low, the fuel level rises and the fuel smell occurs, the fuel is mixed with fuel. If the fuel is milky white, it is water mixed in the fuel. Check and eliminate fuel or water leakage and replace the fuel as required. If the fuel meets the requirements of this type of diesel engine and the quantity is sufficient, loosen the screw plug of the main fuel passage and turn the crankshaft. If more fuel is discharged, the mating clearance of the main bearing, connecting rod bearing and camshaft bearing may be too large. The bearing clearance should be checked and adjusted. If there is little fuel output, it may be blocked filter, leakage of pressure limiting valve or improper adjustment. At this time, the filter should be cleaned or checked and the pressure limiting valve adjusted. Adjustment of pressure limiting valve should be carried out on the test stand and should not be made at will. In addition, if the fuel pump is severely worn or the seal gasket is damaged, causing the fuel pump not to pump fuel, it will also cause the fuel pressure to be too low. At this time, it is necessary to check and repair the fuel pump. If no abnormality is found after the above checks, it means that the fuel pressure gauge is out of order and a new fuel pressure gauge needs to be replaced.

2. No fuel pressure
During the operation of construction machinery, if the fuel indicator lights up and the fuel pressure gauge pointer points to 0, the machine should be stopped immediately and the fire should be stopped. Then check whether the fuel pipeline leaks a lot due to a sudden rupture. If there is no large fuel leak on the engine exterior, loosen the coupling of the fuel pressure gauge. If the fuel rushes out quickly, the fuel pressure gauge is damaged. Since the fuel filter is mounted on the cylinder block, there should generally be a paper cushion. If the paper cushion is incorrectly mounted or the fuel inlet hole is connected with the national fuel hole, the fuel can not enter the main fuel passage. This is quite dangerous, especially for the diesel engine which has just been overhauled. If no abnormal phenomena are found through the above checks, the fault may be on the fuel pump and the fuel pump needs to be checked and repaired.

3. Excessive fuel pressure
In winter, when the diesel engine is just started, it will be found that the fuel pressure is on the high side and will drop to normal after being preheated. If the indicated value of the fuel pressure gauge still exceeds the normal value, the pressure limiting valve should be adjusted to meet the specified value. After commissioning, if the fuel pressure is still too high, the fuel brand needs to be checked to see if the fuel viscosity is too high. If the fuel is not viscous, it may be that the lubricating fuel duct is blocked and cleaned with clean diesel fuel. Due to the poor lubricity of diesel fuel, it is only possible to rotate the starter with crankshaft for 3-4 minutes during cleaning (note that the engine must not be started). If the engine has to be started for cleaning, it can be cleaned after mixing 2/3 of the fuel and 1/3 of the fuel for no more than 3 minutes.

4. The pointer of the fuel pressure gauge oscillates back and forth
After starting the diesel engine, if the pointer of the fuel pressure gauge oscillates back and forth, the fuel gauge should be pulled out first to check whether the fuel is sufficient, and if not, the qualified fuel should be added according to the standard. The bypass valve should be checked if there is sufficient fuel. If the bypass valve spring is deformed or has insufficient elasticity, the bypass valve spring should be replaced; If the bypass valve does not close properly, it should be repaired

Post time: Jun-21-2020