Blowing fuel out of the carb

[DanS]

I have a 79 with 2F, 38 webber. The carb was installed about three years ago at the same time the head was replaced. The rig has run great since the work was complete. I only drive it in the summer - seasonal permit. I went to fire it up for the first time in March and it would rev up then die out, rev up and die out but never idle smoothly. Pulled the filter on the carb, found a few tiny specs, cleaned it out (filter). She fired right up. I let it idle for 10 minutes or so and shut it off. A few days later I tried to take it for a spin but the erratic idling started. Pulled the filter again, found one small spec. Same bad idle. So I drained all the fuel and replaced the filter since it has sat for a few months. No improvement. Pulled the valve cover, all valves seem to be moving, checked clearances , all ok. Took apart carb, was almost spotless, cleaned anyway. Now it wont idle at all. It pops right off, revs up once, then blows fuel out of the carb. Not sure where to look next. The cruiser has always fired right up and ran great the last time i drove it.

Dan

 

[FJforty]

Pull your crankcase vent vacuum line and plug it going to the carb. Give that a shot. Your PCV valve could be stuck.

 

[DanS]

Tried pulling the line. It goes to the intake manifold. No difference. I should add that when I pulled the carb, a plug on the vacuum port was cracked so i replaced it. There is another plugged port on the intake - desmogged - which was blowing off.

Dan

 

[FJforty]

It could be as simple as a bad fuel pump. When it dies can you tell if there is any fuel in the bowl? On my Weber I can see into the bowl from the top, you could also try pumping the throttle and check for squirting fuel. This might confirm that fuel supply is the problem.

 

[Pin_Head]

What do you mean "blows fuel out of the carb"?

If fuel is coming out of the bowl vent tubes and running down inside the carb, then the inlet check valve is stuck open.

If it backfires or pops back out of the carb, then it is too lean to support ignition.

 

[DanS]

Fuel pump is ok. Replaced anyway. No change.

The fuel is backfiring through the carb. If it it too lean, is it just a case of mixture screws? If so, what would cause the adjustment to get so out of whack. It ran great the last time I drove it - although it was four plus months ago.