1999 6.5 in 3500 pickup. 225000 miles pmd relocated long ago, new lift pump and filter, new/rebuilt IP new marine injectors. runs like raped ape. started tap in one cylinder after IP and injectors (same time) swapped injectors and tap stayed with cylinder. crack open fuel to injector and tap stops. tap is high pitch tap not knock. place listening rod on line or injector and sound is right there, not low in motor. taps hot or cold. no performance issues. any experience to help here ?

 

Remove valve cover and inspect the plastic rocker retainers

 

I thought of that. but is it possible that the the lack of, or damage to the plastic retainers will allow the tapping to stop when the cylinder is not firing and resume tapping when it does fire. pulling a valve cover is not a simple exercise with the injector lines wrapped over them.

 

Well if it happened right after injector swap could be tht one injector isnt popping at correct pressure where did you get them? Hopefully not from ss diesel pensacola or diesel care only bosh remans shld be used

 

that's what I thought but I swapped injector with another from a non tapping cylinder and the tap stayed with the cylinder not the injector. purchased through ssdiesel in Tonawanda NY can the ip cause it? ssdiedel was out of suggestions after the cylinder/injector change.

 

Usually bad inj pump will sound like marbles rolling around did you do the tdc relearn procedure using the program to set injection pump timing?

 

Is the tap louder on fire up cold or the same?

 

No performance advantage to having marine injectors no matter what SS Diesel's propaganda says.

The stock injectors can flow more fuel than the IP can provide so marine injectors without the marine IP are a waste of money.
As stated having aftermarket nozzle equipped injectors is a bad thing as well,Bosch,Stanadyne or Delphi are the ONLY acceptable nozzle brands,and SS doesn't use any of them that I know of?
Reports about SS Diesel customer service or lack there of were enough to keep me from ever doing business with them and have only gotten worse over the years.

Might be a carbon issue on top of that piston?

 

to Detroitdiesel idi tap is same hot or cold but easier to hear when warmed up as other diesel noise is quieter. No other new sounds like marbles and haven't heard about tdc relearn. marked and put new pump in same orientation. timing would concern me more if every cylinder tapped. or if performance faltered. to racer55 I've had no problem with ss other than them not knowing what could be causing the tap, they suggested the injector position swap to determine if it was injector or cylinder specific. I can't figure what part in the injection system (we've eliminated the injector it's self as noise stayed with cylinder) or valve train that will only make a tap when the cylinder is firing. if it was valve train related I would expect it to tap if injector was spraying fuel or not, firing or not. it will even stop tapping for a second when I'm cruising and let off the throttle completely. just a split second then resumes. I have been trying to count taps to figure out if it is tapping every revolution or every other revolution. would it tell me more if I knew which stroke it tapped on (compression, exhaust, etc.

 

I would pull the injector and glow plug-light up the cylinder and have look at the piston-might be the remnants of an old glow plug that broke or rotted off?

TDCO relearn is required when an electronic IP is changed-the ECM must "learn" the physical location of the IP,getting it close is not good enough because 1mm difference can be 2 or more degrees of timing change.