Home » Duramax LLY » Duramax LLY – ENGINE DIAGNOSIS – Hard Starting When Hot

Duramax LLY – ENGINE DIAGNOSIS – Hard Starting When Hot


1. Wrong fuel or poor quality fuel.

2. Air leaks in fuel supply (suction) lines.

3. Fuel return or vent line restricted.

4. Low fuel pressure to injector pump.

5. Engine shut-off solenoid problem.

6. Low compression due to rings, pistons, valves.


1. Drain and refill tank. Purge rest of fuel system and bleed injectors.

2. Check lines at fuel pump and injectors for leaks, or loose fittings. Tighten or replace lines as needed.

3. Clear or replace either line if restricted, pinched, or damaged.

4. Replace fuel supply pump if pressure is less than 5 1/2 psi.

5. Test and replace switch or solenoid if necessary.

6.Check compression and overhaul engine if necessary.

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