Spirit7 Posted October 20, 2013 Share Posted October 20, 2013 Hi all, I just picked up a 260z for $250. I'm trying to get the thing started, but I just don't really understand carbs all that well. I started out cleaning the fuel tank and replacing the pumps (electric and mechanical), I had an issue with my original carbs spewing gas from the front, so I found a set on ebay. I can get the car to run for a few seconds off of starting fluid, so I'm thinking fuel issue. I can see the gas window on the carb is about half way full, does that sound right, or should it be full? Maybe I'm not getting enough fuel pressure. Any ideas? Quote Link to comment Share on other sites More sharing options...
Slowpoke Posted October 20, 2013 Share Posted October 20, 2013 You should find the Factory service or Haynes manual 90% of your questions will be awsered in it. You can also do a google search for SU carb tunning. If its been sitting for awhile it could be a bunch of different stuff. I would replace the fuel filter then clean and reset the carbs. Be prepaired for fun times! Post some pics and good luck. Quote Link to comment Share on other sites More sharing options...
Spirit7 Posted October 22, 2013 Author Share Posted October 22, 2013 Ok, I have a FSM downloaded now. I'm a little confused as it does not give me a starting setting for the carb. It starts out saying to warm the engine first (can't do that with it not running, lol). I also looked in the trouble shooting. For "engine does not start" it says... Overflow...I don't have fuel overflowing from the carb. No Fuel Fed to Engine...the fuel pump is working, and there is fuel in the carb. (Possibly bad needle valve??? How would I check this?) Improper Idling Adjustment...It says to readjust, but again, I don't know where to start with the settings. Defective Suction Piston.... Is the suction piston the large metel piece inside the carb that can be raised form the front intake side of the carb? Quote Link to comment Share on other sites More sharing options...
Josh280z Posted October 23, 2013 Share Posted October 23, 2013 I don't know much about carbs as I've never worked with them. However are you running too much or not enough pressure? Quote Link to comment Share on other sites More sharing options...
Spirit7 Posted October 23, 2013 Author Share Posted October 23, 2013 I don't know much about carbs as I've never worked with them. However are you running too much or not enough pressure? It's possible, I don't know much about carbs either. I'll have to get a fuel pressure gauge and see what Im at. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted October 23, 2013 Share Posted October 23, 2013 If you really don't know how carbs work, it is a good idea to find someone who does, their pretty simple and I'm sure you can find someone local. As much as I am for learning on your own, the way the carbs are setup on a Z it can turn into a fire hazard pretty quickly if you don't know how things work. With that said, the FSM is decent for a lot of problems, but I've found British car forums a better help regarding the SU carbs. Is it the stock carb that came on the car? Does it have a flat top on the "bells" of the carb? If so you are dealing with a later set of carbs, which can be a little more difficult to diagnose. If you have checked that fuel is getting to the carb, then you are at a good start. If spraying starter fluid also keeps the car going that means the timing and spark is decent. When the first carbs overflowed, it was most likely a sticking valve. A tap with a blunt instrument should dislodge the valve. Other than that, you would have to disassemble the carb body and find the needle seat and reseat it after cleaning it out. Yes the large metal piece inside the carb that lifts up is the suction piston. It should sit in the housing fairly tightly, but not seized. You should be able to lift it with your pinky with very slight resistance. There is a cap on the top of the carb to add oil to seal the piston and add viscosity to it's movement. For idle adjustment adjust the screws maybe about 1/2 way in, this will get the car started, and looking at the tachometer, lower the screws until it settles at a nice rpm for idle. You will need to pickup a syncrometer or rig a vacuum measurement device via some tubing and balls to sync the carbs together. Fuel pressure should be at 2.5psi I believe, I had a low pressure 4 psi electrical pump and that seemed to work fine. Other than that is the mixture screws, I can't recall on the later carbs, but on the earlier cars I want to say turn them all the way counter clockwise until they seat against the main body and then back out 3 full turns and start from there, sorry please don't quote me on that. You will need a way to test far to determine if you are in the right area with that adjustment either via load testing, an AFR gauge, or the lift the piston while monitoring revs technique. Good luck! Quote Link to comment Share on other sites More sharing options...
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