Cummins x15 knock

Cylinder cutout will isolate it to cylinder, but doesn't necessarily mean it's a fuel knock.

Isolate the cylinder, then look for valve train/jake issues first. If you find nothing and pull the injector, check what you can of the cylinder walls and piston before throwing an injector in

 

It couldn't hurt, but wouldn't be my main goal. What I described should lead to a diagnosis. If it's a knock, they should have isolated the cylinder first. Sounds like they,'re going in blind.

Some others here may have more specific X15 info

@Goodysnap?

 

Cut out is the only way to pinpoint a hole to narrow down. From there swap injectors hole to hole.There is no published compression test for the engine.

Most knocks or noises can be somewhat misinterpreted. The engine is somewhat noisy to begin with. Some of the gear train noises sound like a bag rocks just setting at a stop light.

What’s really disappointing is to tear it down and find nothing. Sometimes it’s just better to run it until it gets worse or to failure. That being said, most bottom end issues are on 5 or 6. Broken rings pistons etc.

 

I always wondered if that bag of rocks sound was normal. The 2350 isx seemed to be the worst with that

 

2350 sound like crap from new

 

Inspect your vibration damper at the front of the engine for for signs of seperation between the inner and outer pieces. It's nonserviceable and can only be replaced. I had 1 engine in the shop 2 years ago that I couldn't find the knock. It definitely had one when test drove. I ran overhead after cold-soak, inspected each cylinder with cut-out test. Finally decided to look externally and I removed the belt and inspected front auxilary and engine components. PFP was the Vibration Damper; the rubber isolator deteriated and caused the vibration at mid-ranged RPM's.

 

Throw a gallon of Lucas fuel and see what it does. Or some 2 stroke oil.