rough running engine

[milveh]

Hi all,
newly rebuilt engine and carb...engine starts right up and runs smooth for about 10 seconds but then runs very rough at idle smooths out a little at high revs but still coughs

 

[jward1]

m37

Make sure you check the inner dist. cap. If its cracked it will run rough and i mean any small crack so check it out good. Take it out of the metal housing to check. also make sure your plugs are not fouled out and wires are good. check your fuel flow for any restrictions and that pump is pumping strong.

 

[WarrenD]

I've heard of rebuilt carbs with the floats set wrong. Does it run any better with a little choke applied? Mine has a slight hesitation when I start from a light but a little choke makes it go away.

 

[longshot2171]

Check your choke. It sounds like it is set too rich.

 

[milveh]

rough running

cap looks good and has new wires...checked plugs and they were black sooty..cleaned and still runs bad...choke is wide open

 

[longshot2171]

Did you adjust the idle mixture screw when the engine was cold or fully warmed up?

 

[Oldfart]

Sooty plugs are a sign of running rich or poor spark. Besides fuel flow and spark, you might check for vacuum leaks. Higher RPM will usually mask a vacuum leak.

 

[smoke]

Check the carb adjustments and float for improper adjustment. Just because it is rebuilt does not mean it good. I had a bronco II with 2.8 carb. Had running problem similar to yours. Rebuilt the carb still had issue. Pulled again check float etc.... left it sit over night full of gas. Came in next morning empty there must of had a hairline crack in the body that leak gas pass everything.I put a new carb on it ran great.

 

[milveh]

adjusted idle screw then warmed up

 

[milveh]

tks all that have responded to this post...I took the carb off today and found gas pooling in the intake manifold...gas was also draining down into the crankcase vent pipe..the one going into intake manifold....thinking it is bad carb...what do you think?

 

[Oldfart]

It sounds like the float needle and seat are bleeding over. Either the float is mal-adjusted or the float and/or the needle are sticking Or there is something in the seat keeping the needle from closing completely. Sometimes fuel pump pressure can be high enough to force the needle open, but this is unusual unless an auxillary pump is used.