What is the reason why a diesel car cannot start when hot but starts normally when cold?
2 Answers
Diesel car cannot start when hot but starts normally when cold because the high-pressure fuel pump is worn out, leading to insufficient pressure when hot. Taking the Great Wall Cannon diesel model as an example: The dimensions of this vehicle are 5410mm in length, 1934mm in width, and 1886mm in height, with a wheelbase of 3230mm. The body type is a 4-door, 5-seat pickup truck, equipped with an 8-speed automatic transmission. The engine is a 2.0T L4 with turbocharged intake, delivering a maximum horsepower of 163ps and a maximum torque of 400Nm. The vehicle features front-engine, rear-wheel drive, with a front suspension type of double-wishbone independent suspension and a rear suspension type of multi-link solid axle non-independent suspension.
As someone who repairs diesel vehicles year-round, I find that the issue of hot-start failure while cold starts are normal is quite common. This is mainly due to insufficient compression caused by thermal expansion—engine components expand under high temperatures, piston ring seals deteriorate, compression pressure drops, and diesel relies on compression ignition. If compression is insufficient, ignition fails. Additionally, fuel pump wear reduces pumping efficiency when hot, and injectors may leak or clog due to high temperatures, leading to unstable fuel supply. For prevention, regularly clean the fuel injection system and change the oil to avoid deposit buildup. Safety advice: if this occurs, do not repeatedly attempt to start the engine; immediately take it to a professional shop for compression testing and fuel pressure checks.
