Diagnosis and treatment of engine idling failure

Author:Dekenag  Alice

There is no idle

The engine has no idle speed, which generally means that the throttle stops when it is at idle speed. When the throttle is slightly increased, the speed increases rapidly, so it cannot operate stably at low speed.

1. The original for

(1) Speed governor idle spring too soft or broken.

(2) The sensor element of the governor is too worn.

(3) The plunger of pin injection pump wears seriously.

(4) Temperature is too low.

(5) Cylinder pressure is too low.

2. Diagnosis and treatment

(1) Cold start without idle, generally normal phenomenon. This is because the temperature is too low, the oil viscosity is too high, which increases the internal resistance of the diesel engine, and the diesel spray and evaporation conditions are extremely poor, resulting in that the diesel engine cannot maintain the minimum and stable running speed. When the throttle is raised after cold start, the engine will shut off quickly. In this case, two methods can be adopted: one is to take preheating or heat preservation measures for the diesel engine in advance, and to warm the oil sump, making the diesel engine temperature higher than the ambient temperature. The other is that after starting, the hand accelerator can be adjusted to a little higher than idle running, and the engine will resume idle running after heating.

(2) However, if the diesel engine has been used for a long time, there is no idle condition, accompanied by insufficient power, and fuel consumption is abnormal. In general, due to excessive plunger wear, oil leakage during idling increases, making the oil supply unable to meet the idle condition requirements, or the cylinder pressure is too low, the injection advance Angle is too large, too small, making the diesel engine combustion conditions poor. As long as we follow the fault treatment of power shortage, idling condition will be restored naturally.

(3) If the above situation is normal, it should be considered whether the idle working element of the governor is abnormal. Check whether the spring of the governor is broken, or whether the speed element has worn away or even the spring is too soft, so that the centrifugal force of the fly hammer in idling operation is far greater than the spring tension to reduce oil, or maintenance personnel improper adjustment. The fuel pump assembly must be removed and repaired on the test bench.

When checking the governor, first adjust through the idle screw, if the adjustment is not effective, then adjust the idle spring pretension. The idle speed spring adjusting nut can be slightly twisted inward or the gasket can be added to the spring seat to increase the pre-tightening force and increase the idle speed. If the spring breaks, it should be replaced and adjusted to restore idle performance.

The engine idling speed is too high, which means that the engine speed is still higher than the idling value when the throttle is raised.

(1) Improper adjustment of throttle lever. The throttle return spring is too soft.

(2) Flange idle stop block or adjusting screw maladjusted.

(3) Jack idle spring is too hard or the pre-tension adjustment is too large.

Diagnosis and treatment

Idle too high is the easiest to check troubleshooting one, first check the throttle to the minimum position, if not in place, check the manual throttle adjustment and throttle back position. Should be loose the hand accelerator to the end, if the throttle still can not return, check whether the throttle return spring is too soft. If it is the fuel pump shortly after maintenance and debugging, it should consider whether the idle speed adjustment is correct, and whether the idle spring preload adjustment is too large. If the spring has been replaced, check whether the spring is hardened.

Idling unsteady diesel engine idling instability in the form of idling operation, fast, slow, or there is a shake, so that the car in the rapid deceleration or shift to stall.

1. The original for

(1) There is air in the oil path.

(2) The oil supply on the low pressure pipeline is not smooth.

(3) Improper adjustment of the brake idling speed stabilizer.

(4) Bad atomization of air injector.

(5) The fuel supply is uneven.

(6) The pin shaft and fork of each connecting rod of the speed governor wear too much.

2. Diagnosis and treatment

When diagnosing idling instability, it should be analyzed, checked and determined according to the service time of the diesel engine and the maintenance degree of the engine.

(1) Diesel fuel injection quality control is not strict, or car diesel engine maintenance is not timely. First of all, check whether the oil supply of the low-pressure oil road is unimpeded, and whether the filter core and mesh in the oil road are blocked with impurities or gel wrap, if any, should be removed.

(2) If the vehicle stops for a long time or the fuel tank fails to be replenished in time, a small amount of air infiltrates the oil path and should be exhaust treated.

(3) If the car has been in use for a long time and the fuel pump has been debugged for many times without checking the wear of the governor, it is necessary to check the wear of the speed element and the joint of the throttle lever. If there is excessive wear, should be replaced or welding repair. When repairing rotating parts, attention should be paid to the symmetry of mass.

(4) The unsteady blade idle speed accompanied by shaking is caused by uneven oil supply of the fuel injection pump. When the oil break cylinder does not affect the change of rotation speed, it indicates that the oil supply of the cylinder is insufficient or the fuel injector is not atomized well. Check the fuel injector first, and then the fuel pump.

(5) If the stable speed device is not adjusted properly, it should be re-mounted on the test bench for maintenance.

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