Hi all. Cylinder #5 on my 2.5L 850 GLT is not firing and I am running out of ideas:
- Spark plug change was overdue so were changed, no change.
- Plug is sparking positively verified.
- Replaced wires and distributor cap with a used set from a working model, no change.
- Swapped injectors of cylinders 4 and 5, no change.
- Checked spark plugs after idling: #5 is wet/shiny, others are not. However, unplugging the injector and swapping plug #5 with a neighboring plug also results in wet/shiny plug.
Maybe important to mention that the oil + filter was changed recently. 200 km after the change I noticed a sudden loss of engine power while driving down the highway, apparently due to loss of cylinder #5.
Any ideas on how to proceed from here?

 

Nice

 

next step would be a compression test. You should see 180 PSI for an NA engine and 150-160 for the Turbo.

 

Okay, need to get the gear for that first though.
In the mean time, I took apart the injector rail again and noticed that the injector tips (the metal part with the needle inside) swivels on two out of the five injectors. One seems to be about to get loose with the other two not moving at all. Is this a problem?

 

Okay, so I did the compression test today. Turns out the affected cylinder has ZERO / 0 compression. I am assuming the more likely cause is a broken valve rather than piston rings or such?

 

you can see if you can get an inspection cam to look at the valves/piston head to confirm but regardless, the head needs to come off.

 

Just to let you guys know: I pulled the head and found the culprit: a chipped outlet valve.

 

you going to try and do the head rebuild on your own? plenty of vids on Youtube... :-)

 

That would be my second rebuild (fixed a busted head gasket first time around), and it's almost done now. But, I'm left with some screws O.O No idea where they came from, any thoughts? I have two of those left...

 

I don't recognize that at all. Ordinarily, I wouldn't post something like that, but in this case, I think it's useful. I am working from home and I have 2 850 engines sitting in my office, and one of them's dismantled.. I have personally removed many alignment pins out of 850 aluminum castings, too. Plus you get a bump and maybe some of the other 850 guys will look.