The control valve is hidden in the "heart" of the diesel pump, and can be called the "fuel manager" of the engine. It mainly takes care of two major things related to power:

Controlling fuel quantity: It is like a precise "diesel faucet", directly determining the amount of diesel injected into the engine. When you step hard on the accelerator, it will open wide, allowing enough diesel to flow into the combustion chamber; when idling, it only leaves a thin gap, just enough to maintain the minimum operating needs of the engine, which is both fuel-efficient and stable.

Stabilizing pressure: It ensures that diesel is sprayed out at a uniform pressure all the time, just like "supplying oxygen at a constant speed" to the engine. If the pressure fluctuates, the fuel injection will be uneven. The engine will shake slightly at best, and at worst, it will "sputter" like a person holding their breath, completely messing up the power output.

Symptoms: When climbing a slope, even if you step the accelerator to the floor, the car still moves up slowly; when overtaking, although you step hard on the accelerator, the speed takes a long time to pick up, as if dragging a heavy load of a thousand catties.

Reasons: The valve is stuck by impurities or worn out over time, failing to close tightly or open fully. The diesel supply can't meet the engine's "appetite", just like a person who can't exert strength because they haven't eaten enough.

Symptoms: With the same tank of fuel, it used to easily cover 1000 kilometers on a long trip, but now it runs out after 800 kilometers, and the fuel gauge pointer drops faster than the vehicle speed.

Reasons: The valve doesn't seal tightly, just like a faucet that can't be turned off properly. Excess diesel is wasted without being fully burned, which is equivalent to opening an "invisible leak" in the fuel tank.

Symptoms: It's especially obvious in winter. After turning the key, the engine "chugs" for a long time. Even if it finally starts, it shakes violently; sometimes you have to turn the key repeatedly, and the battery is almost drained before it starts successfully.

Reasons: The valve's seal fails, leading to pressure loss. After parking, diesel will flow back through the gaps, and air is likely to enter the oil pipe, just like a person inhaling impurities when breathing, which naturally makes it hard to exert force.

Symptoms: When accelerating suddenly, a thick cloud of black smoke comes out of the car's exhaust, like "spraying ink". It's not only scary to look at, but also likely to fail the environmental protection test.

Reasons: The valve responds slowly, and the fuel injection timing is off, causing too much diesel to be injected. The unburned diesel turns into black carbon particles and is directly discharged from the exhaust pipe.

Don't be greedy for cheap when refueling: Impurities and water in inferior diesel are like feeding sand and sewage to the valve, which will accelerate the wear of the valve core and block the oil circuit. Before long, the valve is prone to jamming.

Replace the filter regularly: The diesel filter is the "dust mask" of the valve. Once the filter gets dirty, impurities will take the opportunity to get into the valve. It's recommended to check it every 5000 kilometers and replace it with a new one every 10,000 kilometers or so. Don't wait until the filter "stops working" to remedy it.

Pay attention to abnormal noise warnings: If there is an abnormal "clicking" sound near the diesel pump, especially more obvious when idling, it may be a "distress signal" from the valve being stuck or not moving smoothly. Hurry to find a mechanic for inspection, and don't delay it into a big problem.

Check the pressure before long trips: Before a long trip, especially for old cars, it's better to ask a maintenance worker to check the pump pressure. If the pressure is low, it's probably that the valve is "weak". Replacing it in time can avoid breaking down on the way. Otherwise, if the car breaks down on the highway, the towing fee will be enough to replace several valves.

Last winter, Lao Zhang's car suddenly had unstable idling, fluctuating fast and slow like "shivering". A roadside repair shop checked it and said the pump was completely broken, and replacing it with a new one would cost nearly 10,000 yuan. Lao Zhang was reluctant to spend that much, so he found an experienced mechanic he knew. The mechanic took apart the pump and found that it wasn't the pump that was broken. It was a small piece of iron filings stuck in the control valve, jamming the valve core. After flushing it with a special cleaning agent, the iron filings were gone, the valve moved freely, and the car returned to normal immediately, costing only a few dozen yuan for labor.

So, when the engine is not working properly, don't be scared by the idea of "replacing big parts". Pay more attention to the small part that is the control valve. Find a reliable mechanic to check it carefully. Maybe you can solve the big problem with a small amount of money and avoid wasting money unnecessarily!