What Causes a Diesel Vehicle to Emit White Smoke and Fail to Start?
3 Answers
Here are the reasons why a diesel vehicle may have difficulty starting and emit white smoke: 1. Low engine temperature: If white smoke appears during startup in winter, it is usually due to the engine temperature being too low and not yet reaching optimal condition; 2. Water in the fuel supply system: If you place your hand behind the exhaust pipe and water droplets form on your hand when the white smoke passes over it, it indicates the presence of water in the fuel supply system; 3. Low air pressure in the engine cylinders: If the engine emits white smoke at low temperatures and black smoke when the temperature rises, it suggests that the air pressure in the engine cylinders is too low; 4. Low fuel injection pressure: If the engine emits grayish-white smoke and the vehicle lacks acceleration power after starting, it indicates that the pressure in the fuel injection system is too low.
A couple of days ago, my old diesel pickup had the same issue—it wouldn't start in the morning and was emitting white smoke. I drained some fuel from the tank and found it was full of moisture. Diesel engines are particularly sensitive to this; too much moisture causes white smoke. I also checked the glow plugs and, sure enough, two were burnt out. Without proper preheating in winter, it just wouldn’t ignite. A cylinder pressure test showed only 8 bars of compression, likely due to valve leakage or a blown head gasket. In the end, I had to tow it to the repair shop. The mechanic said this situation required replacing the head gasket and glow plugs, along with a thorough cleaning of the fuel tank.
In my ten years of driving long-haul trucks, I've encountered this issue four or five times. The most common cause is fuel injector failure. Last time my truck emitted white smoke, I found half of the injector's atomization holes were clogged when I opened it up. It could also be misaligned fuel injection timing or a malfunctioning preheating system, leading to incomplete diesel combustion. If you detect a sweet smell, be extra cautious as it indicates coolant entering the cylinders. Such problems are difficult to handle individually, and the only solution is to call a tow truck to take it to a professional diesel engine repair shop.
