3406e cold start misfire...

If its still #5 put a clear hose in return or put return in bucket and see if air is getting in fuel. I have seen intermediate misfires from an ecm but this sounds more like air.

 

Yes, will be visible signs of a inconsistent sealing pattern around the taper on the injector body.also when you torque it down go down to 40-45ftlbs back it off, then back to 48-45lbs. This seats it.

 

Put my money on a failing injector harness.

 

Most of the time you don't find a rubbing issue, they just start losing connectivity and the ends and where the pins crimp in the main connector. It is quite tedious to use an ohm meter and locate an intermittent connection point so CAT usually changes out harness when they suspect a failure, but if your doing the labor I guess you could remove it and test each circuit for continuity while moving the harness around.

Make sure you run the rack before diving into a harness issue, a loose injector can miss when cold then start firing when things warm up a bit, so can a partially plugged injector tip, I would run the rack and replace the spin on fuel filter; fill the new spin on with ATF instead of diesel then fire it up and see if it acts the same. If you find a real loose injector on the rack run chances are the problem will go away, if not the ATF will likely clean out a partially plugged tip if that was the issue.

Then if that cheap and easy stuff bears no fruit the harness would be the next thing I would check out, first doing a cylinder cutout test when it is missing (or a cylinder load test if it warms up and stops missing) will tell you which hole to pay the most attention to as you do the other stuff.

 

I am having same problem right now and I wonder what was wrong with yours ? Thank you !

 

Need to see if it is one hole or all of them. Sometimes firing it up without exhaust manifold on is the truest test.