One cylinder on my 2.5 leaned out.

[streetjeep2.5]

87 MJ 2.5. Ended up with a broken compression ring in cyl 3, and the two broken pieces adhered themselves to the top of the piston. I was told by the looks of the cylinder compared to the others that cyl leaned out on fuel, got too hot, and this happened.

Ever heard of that on a Renix fuel system? If so, what could cause it?

[Geonovast]

Don't know how that could have happened on a TBI motor...

[Eagle]

Don't know how that could have happened on a TBI motor...

^^^ What he said.

 

The '87 2.5L has ONE injector, in the throttle body. The fuel is injected into the airstream as it enters the intake maniforld. Unless you had something very strange affecting the intake valve, there is no way that one cylinder on a TBI engine can get leaned out.

[streetjeep2.5]

So let me ask: what could cause, according to the appearance of what's now "attached" to the top of the piston, the compression ring to break and cause a "divit" in the top of the cylinder wall?

[streetjeep2.5]

Don't know how that could have happened on a TBI motor...

^^^ What he said.

 

The '87 2.5L has ONE injector, in the throttle body. The fuel is injected into the airstream as it enters the intake maniforld. Unless you had something very strange affecting the intake valve, there is no way that one cylinder on a TBI engine can get leaned out.

 

If the intake valve stuck open it would get fuel. make a lot of noise too, but not break a ring. It would have to have remained closed, and that would be a collapsed lifter, but they make a lot of noise too. Maybe put a couple of lifters in that cyl, or a whole new set, just to be on the safe side? Don't want to do that on a 60,000 mile cam, do I?

[streetjeep2.5]

Could the injector itself have leaned out, and only one cyl got hot enough to have damage happen?

[dasbulliwagen]

There is a way for one cylinder to lean out.... there may be a vacuum leak at that intake port, maybe the intake gasket? Or a vac port right above #3 cylinder? I havent looked at mine lately to know if there is a port there or not, but its possible. Do you still have the gasket, maybe it can tell you something.

[Eagle]

There is a way for one cylinder to lean out.... there may be a vacuum leak at that intake port, maybe the intake gasket? Or a vac port right above #3 cylinder? I havent looked at mine lately to know if there is a port there or not, but its possible. Do you still have the gasket, maybe it can tell you something.

^^^

 

Very possible. Good thinking.

[streetjeep2.5]

Will look. Thanks. Is interesting that the bad spot on the cyl wall is on the intake/exhaust manifold side, so a possibility.

[shark]

a hairline in the head gasket will cause a lean condition in the closest cylinder to the crack. ask me how i know.

[streetjeep2.5]

IRT the vacuum leak possibility: The intake gasket looked fine. There is a vacuum port on the runners for cyl 3 and 4, but the lines seem ok. I did notice the head gasket was black on the manifold side while not black on the other side, and at cyl 3 the blackest. When I saw that I wondered if the header from Clifford, being a block hugger type, could have generated enough heat to harm - being black maybe burned - the head gasket and cause the leak. Thoughts?

 

BTW, shark, I'm a-askin, how do you know????