How to check the cause of the under powered truck?Oil article
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WD615 Engine
Common failure of 615 engine

Four major systems that under power the engine

1. Gas path system: including gas supply system and exhaust system

2, oil system: mainly oil supply system and oil products

3, electronic control system: circuit and vehicle computer control system

4, mechanical problems: mainly mechanical equipment failure or configuration problems

Last period explained the cause of engine power shortage of gas road article, this period focuses on the vehicle oil system problems.

First, oil system

For the oil road, we should all know that the oil comes out from the tank, through the coarse filter – hand pump – gear pump – fine filter, from the fine filter is divided into two ways, one way through the relief valve back to the tank.

one way through the oil metering unit.From the metering unit and divided into two ways, one way through zero flow hole back to the tank, the other way into the high pressure plunger, pressure into the common rail, and then to each injector.

A problem with any part of the oil circuit may affect the fuel supply and result in under powered vehicles.For example, the coarse filter is blocked, or the oil and water separator on the coarse filter fails, resulting in too much water in the oil and so on.

The other components of the oil circuit will not be discussed in detail. When a fault is suspected in the oil circuit, the data flow we look at must include the triggering current of the fuel meter unit, as well as the target and actual rail pressure.Through these several data streams to see if there is a fault in the oil circuit.

Here are a few common questions

Two, oil system common problems

1, poor oil quality, water and impurities

Fuel supply system through mechanical control or electronic control, timely and appropriate for the engine to provide clean, no or less containing impurities, water fuel.So poor oil quality not only affects engine power, but also damages components on the oil circuit.

Fault phenomena:

When the engine is running without load, if the throttle is increased, the speed can only be increased slowly;

When there is load, the engine is obviously weak, and easy to flameout, but the exhaust does not smoke;

In overload operation, flameout and a little black smoke.


Check that all fuel filters and oil/water separators are working properly.Can not work normally should be timely maintenance and replacement.When working normally, clean the oil circuit and replace the oil products.

2. The oil circuit is not smooth

Fuel tank filter blockage, fuel coarse filter blockage, fuel fine filter blockage, oil pump internal leakage, return pipe bending blockage and so on will cause the oil pipeline is not smooth, so that the engine fuel supply is insufficient, resulting in power shortage.

Fault phenomena:

Step on the accelerator, the vehicle reaction is slow, the speed of growth is slow, empty car slightly weak, heavy car obviously weak or even flameout.


Combined with the data flow to check the fuel supply to determine whether the oil pipeline is blocked.Replace clogged components.

3. High pressure oil circuit failure

First the injector plunger couple wear too deep, resulting in large internal leakage, is the amount of oil supply can not meet the needs of starting.The second is the oil injection pump regulating mechanism is stuck, so that the plunger can not rotate or rotate too small;

Three is the oil valve seal is not good, four is the injector problem, needle valve adjustment is wrong, the jet hole is blocked;Five is the high pressure oil pipe in the air or joint loose.

Fault phenomena:

Engine no sign of starting, exhaust pipe no smoke.

Loosen the discharge bolt of the injection pump, pull the receiving pump, and abandon the oil at the bolt. However, there is no oil ejection from each cylinder injector, so it can be inferred that the fault is from the high-pressure oil circuit.


The replacement of the replacement, the improper setting of the parts to adjust to the appropriate position to ensure the closure of the high pressure oil circuit.

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