troym
Advanced Contributor
"Still, the same '97 5.7L,
"Still, the same '97 5.7L, 2bbl mercarb. Still hard to start when warm, and still rough idle.
Tore the carb apart, found no smoking gun. Put it back together. With the idle mixture screw completely shut, I can see what I think is a lot more fuel than it needs at idle, flowing from the venturi into the engine. If I keep the throttle open a little past idle, it'll get enough air to keep running... with a little bit of smoke. When I turn it off, I can see fuel continue to pour into the intake for a couple of seconds... which explains the hard starting. And the fact that it's still getting fuel at idle with the idle mixture screw completely shut explains the rough idle. Now for the tough question... what is causing this?
The float is adjusted properly. The needle and seat are new. All gaksets in the carb are new.
Power valve is new. Idle mixture needle is new.
After studying the diagram, I see there is a ball check at the bottom of the accelerator pump cylinder. I haven't messed with that at all... what would happen if that was leaking or missing?"
"Still, the same '97 5.7L, 2bbl mercarb. Still hard to start when warm, and still rough idle.
Tore the carb apart, found no smoking gun. Put it back together. With the idle mixture screw completely shut, I can see what I think is a lot more fuel than it needs at idle, flowing from the venturi into the engine. If I keep the throttle open a little past idle, it'll get enough air to keep running... with a little bit of smoke. When I turn it off, I can see fuel continue to pour into the intake for a couple of seconds... which explains the hard starting. And the fact that it's still getting fuel at idle with the idle mixture screw completely shut explains the rough idle. Now for the tough question... what is causing this?
The float is adjusted properly. The needle and seat are new. All gaksets in the carb are new.
Power valve is new. Idle mixture needle is new.
After studying the diagram, I see there is a ball check at the bottom of the accelerator pump cylinder. I haven't messed with that at all... what would happen if that was leaking or missing?"