#6 cylinder high balance rate

[worley70]

I currently have in my shop a 03 LB7 that is showing a #6 balance rate of 15.0. The injectors have already been replaced, the pushrods are not bent or tweeked, the crankshaft reluctor ring is not damaged. Compression on that cylinder is 60 psi less than the other 7, cylinder leakdown test showed nothing. I have not pulled the head yet, wanted to see if anyone has run across this before or possibly has any idea what may be causing this issue.

[Duramaster]

Does the engine have a misfire? SES light set? What are the balance rates of the other cylinders? Is the fuel filter restricted or worse yet, water in the fuel? :confused:

[worley70]

There is a p0306 for #6 misfire, other balnce rates vary from +0.2 to -3.0 no water or contaminents in fuel aux. fuel filter has been installed and all lines have been cleaned

[Kennedy]

Sounds like (assuming no abuse/racing) an injector may have stuck and torched away at the top of a piston.

[worley70]

Thanks for the tip Kennedy, I will c if the customer wants to pull the head and check it, the truck has 223,000 miles on it

[doodad]

Can just a clogged up fuel filter drive up the balance rate of one cylinder? (Ignoring the code & the low compression) - based on Duramaster's question earlier

[Duramaster]

I was at a class this weekend and I found out that some of the techs are finding pistons "GONE" because of stuck on injectors. I haven't seen that one yet. On the flip side of this, you have new injectors in this engine and you didn't say anything about a fuel knock. So I would have to agree with Kennedy on this one. Have fun!

As far as the clogged filter for one cylinder, I would say no. But, If the tech was not carefull and had knocked some debris into the injector opening during fuel line reinstallation, that could cause the high balance rate.

[rickdlance]

Check for blow-by by removing the oil filler cap and seeing if there is any "steam or smoke' coming out. You could also run a compression check for more info.

[worley70]

Thanks for all the advice everybody, the customer consented to pulling the head. Once off the vehicle I proceeded to pull all the valves on that cyl. and found both exhaust valves totally fried, valve seats heavilly pitted. Intake valves did not look any better. Trying to sell him new head and valves.

[DmaxMaverick]

Excellent report on your find. Any idea of the cause? Inquiring minds want to know....

[Kennedy]

I bought an engine for a core that had 420,000 miles on it and seven sets of injectors. People just never learn that it would benefit them to take some preventive measures. Had this been done, the engine would likely still be running.

This engine had eroded the tops of some of the pistons, but what did it in was an exhaust valve dropped out a jagged chunk like a piece from a jigsaw puzzle. This hit the piston and made a mess of it and the head. Aside from this, I'd say there was no real sign of serious wear and it would have easily gone another 420k...