low compression after run on def

Steve Mutter · June 12, 2018

I have a 2017 f-250 6.7 that was filled with def and ran till it quit. I performed a relative compression and found that #4 was low. I performed a manual compression test and found that #4 is at 100 psi and #2 is at 140 psi. The other two where both around 350 psi so I pulled the head off and inspected. Being so low I hoped to find something. All pistons come over the deck the same amount, cylinder wall look good, piston tops don't look melted and I pull out #4 piston to have a look and don't see anything odd on the rings. I did find if you pour varsol on the face of the cylinder head you can see it leak into the intake and exhaust ports of the two cylinders and not on the other two. I don't think there is enough leakage to account 250 less psi so I am stumped as to where my lose could be. I did perform the manual compression test two different time just to be sure, even pulled the gear off the high pressure fuel pump just in case it was locking up. Have any of you had a 6.7 with base engine damage after being run on def ?

forddieseldoctor · June 12, 2018

Was this before or after replacing the fuel system?

Steve Mutter · June 12, 2018

Have not replaced the fuel system yet, I normally do a relative compression test befor I install a fuel system just in case there is base engine damage.

forddieseldoctor · June 12, 2018

I’ve had 2 trucks that had leaking injectors that messed with the compression readings. I know relative for sure, but I don’t remember about manual compression.

NATHAN · June 19, 2018

I have had 2 trucks that were ran with def in it that caused the high pressure fuel pump to lock up. Once the high pressure fuel pump locked up it caused the crank gear to spin. When I pulled the front cover it was obvious what happened. The 2 trucks I had do that also had fuel pouring out of the high pressure fuel pump and into the engine valley when the fuel pump was turned on. I don't know if the helps but it might be something to look at.

Steve Mutter · June 22, 2018

Update

I assembly the head and put air in cylinder #4 and found air good amount leaking from the intake valves and some out the bottom side of the piston. The insurance company did not want to chance it so they are putting in a long block with fuel system. Now just waiting for parts as most of them are back ordered with no promise date. :banghead:

mchan68 · June 22, 2018

1 hour ago, Steve Mutter said:

Now just waiting for parts as most of them are back ordered with no promise date.

OH BOY!!!!

I feel your pain brother. I just went through a similar scenario with a guy needing a long block about a month ago. The BS I went through with him trying to sort out parts that were available was beyond ridiculous. This business of diagnosing concerns and not being able to obtain parts sure is getting old really fast.