03 DT466E miss

[naturalstatetowing]

This engine is not actually in a bus, but in an International 4300. Originally, it was missing on cylinders one and two and both failed a cylinder contribution test. We replaced both injectors and the valve cover wiring harness. It still had a dead miss on number 1. It passes a buzz test and fails a contribution test. We swapped injectors around and the problem stayed with cylinder one. At the suggestion of the local shop, we checked valve lash and found everything ok. The engine had some miles on it and had some blowby so we tore it down and did an inframe. After reassembly, we still have a dead miss on #1. Since we know it's not the injector, and it passes a buzz test, we assumed computer issues, and swapped the computer with a different truck. Still misses on 1. What am I missing? It's my understanding that passing a buzz test shows a good connection through the harness to the injector driver, and that driver is functioning. Any thoughts are appreciated.

[CHEESE_WAGON]

Could be a blockage in the fuel supply to the injector (ie, even a common-rail could have trash between #s 1 and 2, creating a blockage). This could explain neighboring cylinders misfiring and why one responded to an injector replacement but the other didn't, especially with the one that didn't being on the end of a common-rail (I believe these are common-rail, but not positive).

These do have an Injector Driver Module, I guess a malfunction on one injector is possible, but this sounds more mechanical / physical in nature, like worn component(s) or a fuel system blockage. Other members here are more knowledgeable about specifics, hopefully they'll chime in.

Valvetrain / camshaft problem also comes to mind. I'm not sure if a high-pressure oil pump issue would cause a consistent miss on a specific cylinder. Worn lobe, bad tappet / follower, bent pushrod. Carbon build-up can interfere with a valve closing. Valve can also be bent just enough to prevent closing.

Otherwise I would think about a cracked head or block. Is there bubbling in the coolant when running? Moisture in the exhaust at operating temp? Fluids mixing? Milky oil?

[cadillackid]

has anyone performaed the harness test? the wiring harness itself can be (and often is) the problem of an injection.. not sure how it can pass a contribution test if it is a miss.. a miss means that cylinder is not firing or contributing..


im assuming when you in-framed it you sent the head out to be worked.. valves checked / seats replaced / ground as needed?.. head checked for cracks and planed if any warpage..

[CHEESE_WAGON]

CK, these are wet-sleeve engines, aren't they? Cracked cylinder liner perhaps? Not sure if they have replaceable liners or not?

[ewo1]

Originally Posted by naturalstatetowing

This engine is not actually in a bus, but in an International 4300. Originally, it was missing on cylinders one and two and both failed a cylinder contribution test. We replaced both injectors and the valve cover wiring harness. It still had a dead miss on number 1. It passes a buzz test and fails a contribution test. We swapped injectors around and the problem stayed with cylinder one. At the suggestion of the local shop, we checked valve lash and found everything ok. The engine had some miles on it and had some blowby so we tore it down and did an inframe. After reassembly, we still have a dead miss on #1. Since we know it's not the injector, and it passes a buzz test, we assumed computer issues, and swapped the computer with a different truck. Still misses on 1. What am I missing? It's my understanding that passing a buzz test shows a good connection through the harness to the injector driver, and that driver is functioning. Any thoughts are appreciated.

What Cheese_wagon said, Could be a blockage in the fuel supply to the injector, i would check for that for sure. You never know!

Also, I found this service manual for testing injectors on a DT engine.
I hope there is something there useful to you in your quest to fix your motor.

[Booyah45828]

If it passes the buzz test, I'd lean towards a hard fault issue with the engine itself. Did you have the head gone through when you did the inframe?

See if you can find a shop to do a compression or leak down test of cylinder 1.

[naturalstatetowing]

The head was checked at a machine shop. Fuel is supplied through the head internally, and there is no blockage there. It FAILS a contribution test, but PASSES a buzz test. We assumed hard fault internally as well, however there is nothing there to be faulty at this point. New pistons and liners, cam, lifters, and pushrods all ok, cylinder head checked and ok as well. Injector control pressure is within spec. No codes.

[BusT]

Curious to know what happened here

[bobb]

what tells the injector to fire? cam sensor? crank sensor? bad tone wheel?

[cadillackid]

Originally Posted by bobb

what tells the injector to fire? cam sensor? crank sensor? bad tone wheel?

the ECM fires the injector.. the CPS reads the position.. if it randomly were to miss pulses, the whole injection timing would be off.. if I remember right theres only one indexing pulse during the rotation.


if yours is like the OP and passes the buzz test then id look to compression.. the poor man's compression test is to unplug the harness and crank the engine.. listening for even-ness of cranking..


otherwise it comes down to having the injectors tested.. it is technically possible that the injectgor passes a buzz tests .. "clicks".. but the fuel inlet holes or nozzle is clogged so no fuel actually makes it into the cylinder...

[Booyah45828]

Originally Posted by bobb

what tells the injector to fire? cam sensor? crank sensor? bad tone wheel?

Both.

It uses the cam sensor to figure out which stroke(exhaust vs compression), and then the crank sensor to accurately time it.

If either would be bad, a code would likely be given, along with a no start. Very rarely would it cause a miss.

[bobb]

did you crank it with the valve cover off to verify valve action?