Mercruiser 5.7mpi horizon single cylinder burning lean

[nola mike]

I'd throw on a vacuum gauge and do a leak down test (real one using leak down tester).

 

[alldodge]

With Pics working again, can you post the plug?

It could be while running a tad lean, might not be enough to worry about

 

[woodworker2001]

With Pics working again, can you post the plug?

It could be while running a tad lean, might not be enough to worry about

This is the plug after running a bunch of miles

This is the photo of the injector port on that cylinder

 

[woodworker2001]

I'd throw on a vacuum gauge and do a leak down test (real one using leak down tester).

That is next on the list but have to get a leak down tester

 

[alldodge]

My guess
I think it's running for the most part fine.

There is black around the plug and tip is real clean. The injector port is rusty (should not be) so there is moisture getting in some where. There should be no rust on the ports. Might have a small intake gasket leak which is steam cleaning the plug

 

[woodworker2001]

My guess
I think it's running for the most part fine.

There is black around the plug and tip is real clean. The injector port is rusty (should not be) so there is moisture getting in some where. There should be no rust on the ports. Might have a small intake gasket leak which is steam cleaning the plug

Not showing any signs of coolant use with fresh water cooled engine…. Not saying this isn’t the case. Most definitely something going on here

 

[alldodge]

Another thought, if injector seal is not sealing tight then could be vacuum leak as nola mentioned. The issue is why isn't the leak effecting the nearby plugs (that is the puzzle)

 

[woodworker2001]

Another thought, if injector seal is not sealing tight then could be vacuum leak as nola mentioned. The issue is why isn't the leak effecting the nearby plugs (that is the puzzle)

I have changed that injector with new orings…. But those are individual to each cylinder so if it was leaking air then could be the cause. What’s the best way to test that…. Would be a new intake if that is the case I am assuming…

 

[alldodge]

I'm still thinking that if it was a vacuum leak then there would be more then the one cylinder. To test use a vacuum gauge and connect with a Tee to the vac line that goes to regulator.

Teeing with the Reg is going to be a real small line so may not respond very well

 

[kenny nunez]

Have you tried removing the fuel rail nd blowing it out with compressed air.
Maybe there is something stuck in the rail in the fitting that the injector plugs into.

 

[woodworker2001]

Have you tried removing the fuel rail nd blowing it out with compressed air.
Maybe there is something stuck in the rail in the fitting that the injector plugs into.

I did not blow air but the hole is plenty pig to visually inspect and it was all good

 

[woodworker2001]

Ok still need to get a leak down tester but that motor is using a small amount of coolant. I think steam cleaning of the plug due to a head gasket or intake gasket leak might be the culperet. I will report back when I get some more testing done