Theories on rear engine fuel leak?

[Learjetter]

Gang,

AP/IA out of pocket until the weekend. Opened Pilot side rear cowl and noticed blue staining near #3 cylinder on baffle and below #3 cylinder on engine Mount tube. Anyone want to hazard a guess or propose a theory for us to look at? See photos.

Non-turbo, G-model, TCM IO360-G. Running the boost pump on high with engine off did not result in any obvious leaks.

Has anyone had a problem like this before?

[JAG]

Have a good visual look at the fuel line to the nozzle and see if it has a hole or crack - it could have been rubbing on cylinder fin. I know I have replaced 3 due to this (prior to leaking or failing). nozzle could be clogged? Can you check your engine monitor data from last flight and see what #3 cylinder was doing?

Jeff

[MD83driver]

It is interesting that there are fuel stains on the Front side of the spark plug away from the fuel injector line.

[Jhogan0101]

I have one of these lights, pretty bright. Maybe you could route it through the cowl flap and mount in a few different positions. Bit of a pain in the ass but i think you’ll see the problem.

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[mshac]

Look at the black carbon on the back of the spark plug!!!! Leaking fuel has been burning off there for hours, probably leaking from the injector near it!!! Only by the grace of GOD have you not had an engine fire.

[wslade2]

Agree

I think I also see some slight carbon on the injector nut (side facing spark plug) and on fins below injector. Highly suspect a leak at injector line-nut-injector. Those welded joints where the compression fitting is like to crack. At least that’s what I’ve run into.