خنک‌کن سوخت خراب

The heat exchanger that cools fuel returning to the tank, failed or blocked so returning fuel arrives hot. Many high pressure diesel systems need one, because fuel absorbs a great deal of heat from the high pressure pump and the rail and is recirculated continuously.

Hot fuel is a real problem rather than a monitoring detail. Its density falls, so a given volume delivers less energy; its lubricity falls, which shortens pump life; and the tank warms until the module reports fuel temperature above its limit. A fuel temperature code with a healthy sensor points here, and the corroborating evidence is a tank that is genuinely warm to the touch after a long run.

It is usually air-cooled and mounted low, so it blocks externally with road debris exactly like a small radiator, or corrodes through. Check airflow across it and compare fuel temperature before and after — a cooler with no temperature drop across it is not working, and a blocked one is often obvious once the underside is inspected.