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cylender failure in F250B with 350 hours, huge carbon build up on spark plug

el segundo

New member
On a F250B model year 2008 (V6 with right side head/center cylinder failure), the starboard center sparkplug and cylinder walls are completely coated with carbon. The motor was bought in 2013 and has 350 hours on it and just out of warranty.
The plugs went 200 hours (125 hours to 320 hours) without changing, when I tried to remover the starboard center spark plug I found it impossible to remove spark plug. It took 5 hours with impact wrenching and ring free/penetrating oil sprayed repeatedly drilling in and out repeatedly to knock down the large popsicle of carbon buildup of the spark plug tip. The diameter of the carbon clump was too big to get out of the cylinder head. What would cause this?
After 20 hours, I changed all spark plugs again. Again, it appears the problem is going on still. Does anybody have an idea of what the problem is?
My guess is there is no spark, BUT, without heat, how does the carbon build and deposit on the cylinder walls and plug?
If anybody has an idea on how to address the problem, I would appreciate the input. Again, the motor is 1 year out of warranty but obviously, the problem went undiagnosed for several years.

Matt
 
Pull the fuel injector and have it tested.
I have a plug in the lights up if the injector gets a signal. My plan was to plug that in tomorrow and see what it looks like. Also have a light that goes on the spark plug-was going to check that too.

I'll plan on pulling the injector tomorrow after my test, perhaps I should order a new one now??
 
atomization PASSED
leak test PASSED
FLOW RATE 70CC @ 3 BAR 30 sec

The shop (Diesel commerial repair) thinks it might be intake valve, just a guess
 
Chris it passed the leak test post#5 Elsegundo if it passed a leakdown test the valve train should be fine,find another repair shop
 
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