My '73 xj6 has been a pain since I've owned it, however I am getting it very close to reliable. The problem I am having is when I just turn the key it leaks a lot of fuel. It also leaks a bit after I turn the engine off. I have replaced the fuel tank, cleaned the pump, replaced fuel filter, rebuilt carbs, set float height according to spec (16.5 + or - .5) and all that. I cannot figure this out. My only guess at this point is fuel pressure too high. The pump it's pulling from isn't stock, but it's similar to stock. I checked the pressure off the line feeding the carbs and am getting about 5.5psi. If I remember correctly these carbs don't like much more than 4psi. Is the extra 1.5 psi enough to overpower the needle and seat? Is my best course of action at this point to install a regulator or are there other options for needle and seat that might work too? I have the carbs off again and would like this to be the last time they're off for a while. ANY help would be great, this is driving me crazy.

 

When you rebuilt the carbs did you replace the needle and seat?
Maybe worth rechecking the float height setting, try setting it too low to see if the fuel still gets past, but don't leave it there as it will run lean.

 

The carbs need to be updated to use today's fuel and also install check valves to shut off the gas flow to the carbs. I did this to mine and it really made a big difference. Make sure that the throttle shafts are line bored and sealed well, too. Also use starting fluid spray in the can to check for vacuum leaks on the shafts and vacuum lines. The engine will speed up if there are vacuum leaks.
Not my project but a good read.

https://xkeresto.wordpress.com/page/2/



Ball Valve Grose jets, with Viton seals.

 

Strombergs?

This discussion =

TR250/TR6 Carbs Part I

is the best source I know of for a super thorough but highly practical blow-by-blow analysis of Strombergs.

I had the same trouble for awhile: I got so tired of pulling those carbies. You may have some fuel pump issue -- I don't know about that as my pumps are stock -- but I had to do all three classic things to stop the leaking: change valve in float chamber, change diaphragm, and put on new gaskets. Got the kits from Joe Curto in NY. If you did all that then, yes, maybe there is some pump issue

 

I had this exact problem with my HS8 SUs on my '73 XJ6. Replacing the Needle Valve sorted the problem. Just be careful with replacement carb parts. On the HS8 at least, the replacement Needle Valve didn't need a crush washer, where the original parts did. This meant that initial replacement didn't initially work. Once the crush washers were removed all was good.

 

I had exact same problem, but tried the local suppliers complete stock of needles and seats before I tried that.

 

First off, thank you all for your input. I ended up swapping out the needle and seats on both carbs and readjusted the float level (not sure I really changed anything). I got the carburetors back on, turned the key to "ON" and no leak! It then started right up which got me excited, but if there's one thing I've learned from this car, it's to never assume you DON'T still have a problem. With choke about half way out, it was idling smooth and relatively quiet, which was actually cause for concern...


My new problem: The rear carburetor is running too lean. So lean, in fact, that pulling the plug wires off the rear three plugs (one at a time) changes absolutely nothing. I can choke out that carb by hand and it fires up those cylinders. Alternatively, if I take the damper out and use the adjusting tool to put light downward pressure on the air valve, the cylinders start to fire. The diaphragms in both carbs are good and there is fluid in there as well. I have no idea what is going on at this point... I plan on reading through the link that series1fan posted to see if there's anything I missed that may be useful, but figured I'd post an update and see if anyone knows what may be going on.


I should also add: I took the float bowl off and had plenty of fuel in there, so I don't think my floats are set too low.