Engine knock

[Bob Anderson]

Has anyone had this happen? On a recent trip towing out travel trailer (8,000 lb. ) my Cummins knocked at 2500 RPM pulling a 7 % hill in 3rd. gear. Backed off immediately and it quit. Advanced the throttle and it would knock. Drop RPM's to about 2200 and no knock. Got up hill ok. No warning lights lit, etc. This happened 3 times in 9,000 miles. There was no loss of power. Just loud.

 

[redneckdr]

knocking

sounds like it might be "fuel knocking", a condition discussed in my C8. 3 manual. the C is a 92, so mechanical engine control. i chased it for awhile and then gave up. adjusting the valves, retiming it, and pulling the injectors for inspection and pressure check--didn't change it. i don't like to hear it, so like you i back off when it occurs. my new isb hasnn't done it so far. maybe poor quality fuel??? if not maybe ecm not timing it quite right?? someone else may have more ideas, but i'll bet it is fuel knocking--pre-igniting somewhat like gas engines do on low octane gas.