Yep, another problem - Front SU is leaking

[ktm]

The front SU carb is leaking. At first it was blowing gas around the banjo fitting gaskets. When I say blowing, I mean there was a veritable river of gas pouring from around the fitting.

I pulled the float cover off, cleaned and checked the needle, and checked the banjo fitting and passages. No dice.

I bought a float maintenance kit to replace the gaskets. A new needle valve was included in the kit. Last night I replaced all the gaskets and needle valve and decided to check the float level. Boy was I surprised when the float would not even TOUCH the needle valve. Giddy, I reassembled everythign after setting the float (by the way, how do you measure the float setting? I did it, but there has to be a better way).

This time it was not POURING gas out of the banjo fitting, but you could see that it was leaking around the fitting (yes, its tight). I was getting NO fuel out of the vent hose. Nada. Zip. Zilch. Zero.

A new problem manifested itself - now I have fuel leaking from the front of the carb. The air piston moves freely and I have enough oil in the damper.

It's my understanding that the 1972 carb (yes, its a 3-screw) float is plastic, and as such will not sink over time.

Everything I have read points to a float/valve issue, but short of replacing the float, I have done everything that I can.

Help me Obi, er, Classic Zcar Club, you are my only hope.

Edit: Upon further transcedental thinking due to copious amounts of coffee, could my jet needle be clogged? This is the only other thing I can think of. I need to check my float cover vent as well. I should not be blowing gas out of the banjo fitting and not the vent if its a float problem.

[beandip]

I don't know what up with the banjo fitting , but the fuel running out of the intake of the carb is VARY LIKELY DUE TO THE FLOAT BEING SET TOO HIGH. This will cause the gas to pour out of the fuel nozzle and into the throat of the carb. Gary

[ktm]

Gary, correct, but I never had that problem until I replaced the valve and set the float. Before the float did not even TOUCH the needle valve. I should have been pouring gas out of my carb throat and vent hose earlier but was not.

Here is the really odd thing. The first time I saw gas pouring out of the banjo fitting, I removed the float bowl cover and noted that the bowl was 1/4 fuel of full, that's it. This is when the float was not even TOUCHING the needle valve. So I figured I had a stuck valve/debris in banjo fitting which was blocking the flow and causing it to come out around the banjo fitting.

I love this car. I love this car. I love this car. I love this car. I love this car. I love this car. I love this car. I love this car.

[ktm]

Solved the problem. I KNEW it was a float and/or needle valve problem, but nothing was making any sense in light of historical performance. An obscure statement by Bruce Palmer as well as a tip by another member helped.

[=Enigma=]

I had a problem getting the aluminum gasket on the banjo fitting to seal. I tried new ones and copper ones to no avail. I finally got the leak stopped by going with plastic washers. The leak was barely detectable but you could smell it.

[1 Bravo 6]

G'Day Bo,

Glad to hear you solved the problem. I've been wrestling with the same problem of fuel coming out of the front of the rear carby now for over three weeks.

I tried everything I could think of, finally gave up and dropped the problem into the lap of a carby expert, and it's got him stuffed as well.:disappoin So far he's used three needles and adjusted the float, to no avail. We know it HAS to be a needle/float issue but, to be absolutely certain, when I've got the time I'm going to swap the float/needle setup between the carbies. If the front carby floods it'll verify the cause.

Wish me luck.

Rick.

:devious: :devious:

[ktm]

1 Bravo 6, my problem really stumped me as I did not have any of the secondary signs of a float problem such as a full float bowl. I would get gas to come out of the banjo fitting and/or vent hose, but when I remove the float bowl lid, there was around 1/5-1/4 of gas in the bowl.

Last night I read a statement by Bruce Palmer that if you set the float seat to 9/16-in. by inverting the float cover, you'll set the float too low. Another member said that his mechanic would adjust the float level until the top of the float was almost parallel with the float cover. If you do the latter, you will measure 9/16-in. from the FRONT edge of the cover versus the middle part.

There is a lip surrounding the cover. I kept setting my float to 9/16-in. as measured from the front edge of the float to the bottom of the cover. I changed that to 9/16-in. as measured from the little lip surrounding the cover and it solved my problem.

A final trick (beandip told me this and I read it numerous times in the archives) is to measure 23 mm down from the top of the float bowl (with the cover removed). Attached a clear hose to the bottom of the float bowl and hold it next to the mark on the float bowl. The fuel level should match the mark. Keep adjusting your float seat until it matches.

I intend to do this as a check this weekend.

[beandip]

1 Bravo 6, my problem really stumped me as I did not have any of the secondary signs of a float problem such as a full float bowl. I would get gas to come out of the banjo fitting and/or vent hose, but when I remove the float bowl lid, there was around 1/5-1/4 of gas in the bowl.

Last night I read a statement by Bruce Palmer that if you set the float seat to 9/16-in. by inverting the float cover, you'll set the float too low. Another member said that his mechanic would adjust the float level until the top of the float was almost parallel with the float cover. If you do the latter, you will measure 9/16-in. from the FRONT edge of the cover versus the middle part.

There is a lip surrounding the cover. I kept setting my float to 9/16-in. as measured from the front edge of the float to the bottom of the cover. I changed that to 9/16-in. as measured from the little lip surrounding the cover and it solved my problem.

A final trick (beandip told me this and I read it numerous times in the archives) is to measure 23 mm down from the top of the float bowl (with the cover removed). Attached a clear hose to the bottom of the float bowl and hold it next to the mark on the float bowl. The fuel level should match the mark. Keep adjusting your float seat until it matches.

I intend to do this as a check this weekend.

Remember , I qualified the information with '' I havent done this myself but others have and had good results " Gary:cross-eye

[Arne]

I have done that check, and it works well -- but you must have the fuel pump running while you do it to get good results. Which makes it difficult (to say the least) if you don't have an electric fuel pump.

[1 Bravo 6]

Bo, Gazza, Arne,

Just thought I'd mention that I told the carby expert ( "X" is an unknown quantity and a "SPURT" is a drip under pressure) about setting the float 9/16 as per your posts and guess what???????? IT WORKED!!!!!!!!!! no more fuel pouring out of the front of the rear carby.

Thanks all.

Rick.

:devious: :devious:

[1 Bravo 6]

My apologies for regurgitating an old thread but I want to add some info that might be of interest.

Two days after my last post on this thread the damned rear carby began spitting fuel out the front again. Needless to say, that really P'd me off. The bloke from the carby shop was stumped for ideas at first but he came up with a suggestion that WORKED.

I have a pair of 240Z carbies fitted to my 260Z. What we did was to remove the top of the 240Z fuel bowls, needles and seats and replace them with 260Z tops, needles and seats.

Not only has it fixed the fuel leak, but I swear the engine is running smoother.

Rick.

:devious: :devious: