Too much fuel pressure or float issue?

[Hardway]

I just got my '72 240z running again, for about 5 seconds. I installed a Carter P60504 electric fuel pump with an advertised shut off of 4psi. From what I have read the SU's do not like anymore than 3.5psi. Upon turning the key and letting the system prime fuel started pouring out of the air cleaner/intake side of the carbs at the bottom of the large opening. I unplugged the fuel pump, waited a minute, turned the key, and the car would run until it emptied the fuel in the carbs. So my question is, if the floats and needles are working properly would the keep fuel from filling up the carbs and leaking out? If my floats and needles are fine then I am pushing too much pressure in to the carbs and bypassing the needle and seat shutoff int he float chamber? I have not opened the float chambers yet as I wanted to have some float gaskets on hand before doing so. I had also posted up in the Engine section about my return fuel line. It is crimped but I can still blow air through it. Below is a picture. Should I consider finding a new fuel rail?

[madkaw]

Yes , the fuel rail return side is a metered orifice, I would replace it.

Time to take a look at the floats , I would think the needle and seat would hold 4psi. It might be a combination of the two items.

[palosfv3]

Its not a bad idea to replace the fuel inlet valve assembly . They can wear out and hang up as described. We had one here that just drove us crazy with intermittent fuel problems until we replaced the assembly. Make sure your rebuild kit has the valve assembly.

[olzed]

Another fuel rail would be the way to go, but before you do that,

if you squeeze the return line the other way you might be able to open the orifice again. It may give an indication if that is your problem,

[Bruce Palmer]

The fact that both carbs do the gushy thing "together" strongly suggests it's fuel pressure holding the needles and seats open regardless of what the floats are trying to do to close them.

And you're right, floatbowl lid gaskets tend to turn into potato chips once the lid is removed making them a B-i-t-c-h to reseal. We sell em' for $2 each and everyone of you Hitachi'd guys should have spares.....

[Hardway]

Thanks for the info guys. I opened up the float bowls this evening and found a few small surprises. First the good news, the floats appeared to be in excellent and the bottom of each fuel camber was pretty clean with about 1/4 of fuel left in each bowl. Now on to the surprises, the float was way out of adjustment on the front carb but even worse I could blow any air through the fuel inlet and pass the needle and seat. I took it apart and there was not any debris in it and the needle itself looked good. However I put it back together and was able to blow a little air through it but once I closed it I could not get it to open again.

On the rear carb I could tell someone had been in it and recently since the gasket looked a lot newer. Upon getting the float lid off the entire needle assembly fell apart on the garage floor. I am not 100% sure I found everything but somehow the parts got past the retaining spring. One thing I found odd was the tip of the needle for the rear carb had a rubber tip on it. At first I thought it was a lot of dirt but then it flexed. It seemed to be in good shape so I put it back together but think a second small spring is missing as it does not feel like there is enough tension on it. I have a rebuild kit on the way from the local parts store but I will be calling Bruce tomorrow to order some more float bowl baskets as his description is spot on for the gaskets being like a potato chip. I also cleaned the hinge pins for the floats as they were mildly corroded. A little time and some fine steel wool and they were smooth once again. One disturbing surprise was the oil in the dome pots appears to be auto. trans. fluid since it is red. From what I have read online and in my manual 10W-30 oil should be used. Is there some reason behind using ATF? Do I need to drain it and refill it with 10W-30?

On a side note, with so many cars running SU type carbs why doesn't someone make a re-usable float bowl gasket and charge like $20 for the pair? I would gladly pay that and even a little more to not have to mess with replacing them all the time.

Edited August 7, 2012 by Hardway

[Bruce Palmer]

I have been using out of the same quart can of ATF for SOooooo long the can is made of cardboard. Ask any 12 guys what to use, you'll get 27 different answers.

[Hardway]

IT RUNS!!! I picked up a rebuild kit for each carb along with a Holley Adj. FPR. Had to make two trips to the parts store to get the right fittings for the regulator. Got the new float needle assemblies installed, adjusted the float to 23.6mm for each, and installed the AFPR. I lucked out as I used one of the threaded mounting holes that I guess would have held the charcoal canister bracket to hold the bracket for the regulator. I turned the key to let the system build pressure, no fuel gushing out of the carbs and no leaks to speak of. (YAH) Turned the key all the way and she roared to life on the second turn of the engine. I let it run for awhile so I could check leaks and everything looked good. I blipped the throttle a few times and she sounded great but I think it is running a hair rich based on the smell of the exhaust. It was already 10pm and didn't want to get carried away so I shut off and will hopefully get to drive it around the neighborhood tomorrow after work.

Thank you again to everyone for your help and Bruce, it was good talking to you earlier today and will be on the look out for the float bowl gaskets.