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carb leaking gasoline


zanos

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Hello,im new to this forum,and Z's overall.I just got this 1972 z with L28 engine swap.I have dual SU carburators,and dont know anything at all about carbs.Well,i was driving the car for a week(and was really enjoying it :knockedou ),BUT then it happened to rain in los angeles,and something happened.The car would drive really rough first,then its stopped going over 3k rpms at all.I stopped to check whats up,opened the hood,and saw that one of the carbs is leaking gasoline pretty bad(one thats closer to a driver).When i stepped on the gas,the leaking would stop,but would start again when car is on idle.I tried checking all ignition stuff,plugs look ok,car got new wires,EL dizzy........What could it be,did the carb went bad?Well,thanx in advance.

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Each carb has a separate bowl that contains a float. The purpose of this is to regulate the amount of fuel available to the carb. When the bowl fills up the float raises and pushes on a needle valve that shuts off the fuel flow. As the carb consumes fuel the float goes back down which in turn lets in more fuel. What happens sometimes is that needle valve gets stuck open, usually due to debris in the fuel. Even though the float is trying to close the valve it stays open. There are actually hoses from the top of each float bowl that go straight to the air cleaner as a way of handling this accidental overflow but if float bowl lid gaskets are not good fuel will leak out there. When you step on the gas the carb consumes fuel which in turn lowers the level and stops the leak temporarily.

It's fairly simple to remove the lid from the float bowl to diagnose and fix the problem.

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Cracked hoses shouldn't cause fuel to overflow out of the carbs, maybe from under or around, but a stuck needle jet in the top of the fuel bowl cover can let too much fuel in to the bowl, and also a float inside the fuel bowl may be hung-up or out of whack and not closing the needle jet when the fuel is at it's proper level inside the bowl.

Another thing that can cause fuel to come out of the carb is a plug fuel bowl vent hose that vents out the top of the fuel bowl cover. The hose vents to the aircleaner or an outside overflow canister. It you restrict the free airflow within this hose, fuel will overflow out of the carbs.

Search SU carb fuel related problems, there are alot here, the reading will educate you with some ideas to look at. Then there is always the ZTherapy SU carb videos that will get you straight with these wonderful carbs.

Good Luck.

Sounds like debris or adjustments.

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thanx,that fixed the problem.What an easy fix :knockedou Thanx for all the replies,really appretiate it

Each carb has a separate bowl that contains a float. The purpose of this is to regulate the amount of fuel available to the carb. When the bowl fills up the float raises and pushes on a needle valve that shuts off the fuel flow. As the carb consumes fuel the float goes back down which in turn lets in more fuel. What happens sometimes is that needle valve gets stuck open, usually due to debris in the fuel. Even though the float is trying to close the valve it stays open. There are actually hoses from the top of each float bowl that go straight to the air cleaner as a way of handling this accidental overflow but if float bowl lid gaskets are not good fuel will leak out there. When you step on the gas the carb consumes fuel which in turn lowers the level and stops the leak temporarily.

It's fairly simple to remove the lid from the float bowl to diagnose and fix the problem.

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