Help - Carb Leaks And Won't Start After Rebuild

[JR Ohio]

This forum has been very helpful to me in the past, and any advice with this situation would be appreciated.

Here’s what I have. ’72 240Z, stock L28, 3 screw round top carbs. I finished rebuilding the carbs yesterday. After getting everything reinstalled, I turned on the ignition to check for leaks and they were there. Leaks from the banjo fuel fitting supply to the bowl and also some leaks around the float bowl top gasket. I tightened the 4 bowl top screws and the banjo fitting bolt, but they seem to still ooze fuel.

Current plan – Take it back apart and put some Permatex non-hardening sealant & dressing (#85409) on the parts and reassemble.

I’m pretty sure I have the float levels set correctly. I used a gauge when I installed the needle/seat and float. I also put a clear line on the fuel output to use as a sight gauge and all seems well.

There may be another problem possibly related or possibly not. After tightening things up to only an ooze of leaking, I attempted to start it up. No luck. It did sputter a few times but never got it running. As it was getting late, I stopped for the night.

Things I am going to check on the non starting situation – Pull the domes & pistons to check the fuel level at the metering needles’ seats and re-check the mixture for the initial 2 ½ turns down from top. I’m also going to check the level of the oil in the dashpot. I may have them slightly overfull, but don’t think this could be the culprit as I unscrewed the top of the plungers and it did not help.

I got the car running pretty good prior to the rebuild. The reason for the rebuild was a fuel leak around the front carb’s bowl. Discovered the float level was way too high and the previous owned evidently lost or damaged the gasket and put it back together with only RTV. Finding that, I decided there may be other things he had done. Found a couple minor things in the process. (oil in one dashpot and hardly any in the other, different fuel feed lines that both looked like they were ready to fail)

Would like to have any additional diagnostic advice or tips beyond all of the above or about the above that you think may help.

Thank you for any and all help and advice!

John

[Captain Obvious]

I’m pretty sure I have the float levels set correctly. I used a gauge when I installed the needle/seat and float. I also put a clear line on the fuel output to use as a sight gauge and all seems well.

Did you do the clear line check on or off the car? If you did it off, I would recheck it on the car.

You used new bowl gaskets and banjo washers?

[JR Ohio]

Hi Captain!

And thanks for the quick post!

When I did the clear line check, the carbs were on the car. I did that to be certain that they were at the correct angle for an accurate reading.

The kits came with new gaskets and banjo washers which I used. The old banjo washers were metallic ones probably from the factory since the bolts were on pretty tight. The new ones are reddish fiber ones. Thinking of putting on a little removable sealant and cranking on it to be sure it seals up. Also thinking of the same on the float bowl but not crank quite as hard because of the size of the screws and material of the bowls.

1st step is to get it to stop leaking/oozing then 2nd step is to figure out why it wouldn't start.

Thanks for your assistance and letting me tap into your knowledge!

John

[Captain Obvious]

If you did the float level on the car I have confidence in the results.

I've never experienced the bowl gaskets leaking with new gaskets. They always seemed to do a good job of sealing. I guess it's possible that there is some flaw in the bowl lip or cap sealing surface that the old gasket was able to compensate for, that for some reason, the new gasket cannot?

I have seen the banjo washers leak though. I solved that problem by simply loosening them up a little and then cinching them up again (maybe a little tighter than they were last time?). Failing that, you could try reusing the old metal washers.

I wonder if maybe what you think is a leaking bowl gasket is actually fuel spreading from the banjo bolts and the bowl gaskets are not really leaking? Gas, being thin and volatile, spreads rapidly...

[JR Ohio]

Hey Captain!

Bingo! the fuel leak that I thought was the bowl gasket is actually the banjo leaking. I have not fixed the banjo leak yet, but I did dry things up and put a mirror in there to watch and that's where it's coming from. With the float level set correctly, there would be no reason for the gasket to leak.

So tomorrow, I fix the banjo leak. Might take the red composite ones off and put the metal/aluminum ones back on to see if that solves the problem. Really don't want to put goop on it if I can avoid it.

The next project will be to try to figure out why it won't start!

Thanks for the tips,

John

[Captain Obvious]

Excellent. Either a little tighter on the current banjo washers or going back to the old washers then.

Even though the bowl gasket has been cleared of issues, I do have one more thought about that part...

With the float level set correctly, there would be no reason for the gasket to leak.

I was originally thinking the same thing, and that's why I asked the question. But after I asked the question I started thinking that it probably wouldn't really matter. The fuel level may be below the level of the bowl gasket when sitting static in the garage, but as soon as you hit the road and the fuel in the bowl starts sloshing around, that gasket is going to be completely bathed with fuel pretty much all of the time even if the bowl level is correct.

So the bowl gasket has to be a positive seal even if the fuel level is correctly below the level of the gasket. In other words, you can't get away with a poor bowl gasket even if the fuel level is at spec.

[Stanley]

Had a leaky banjo until I polished both sides with 600 grit sandpaper. Also had to use the red composite washers, the old aluminum ones needed a crazy amount of torque to stop leaking.