240z running rough

[rosaaen89]

2 hours ago, Patcon said:

My first concern isn't crud in the tank if it's been coated. My first concern is you have a stopped up fuel or return line or the tank pick up is clogged with tank sealer

i’ll try to run the baby bottle of fuel right before the pump to see what happens and let you guys know what happens. if the line is stopped up is the only way to get around that just replacing the hard lines that run from the tank to the engine bay or is there some way to get them cleaned out 

[rosaaen89]

so late last night  i took the pistons off the carbs and the front one looked good but the rear was all black and inside looked like there were scratches or indents. thinking the needle might be causing issues ? 

 

 

first needle is the front carb others are of the rear

[Mark Maras]

 Clean everything carefully with lacquer thinner and raise the nozzles to the top (usually up 2 1/2 turns?). Install the domes and pistons without oil and without the shock absorber "jiggly bits". Verify both pistons bottomed out, then lift them slowly to their top positions and let them fall. The stroke of the pistons should be smooth (no resistance) from bottom to top and top to bottom and nearly identical in drop time. If you encounter resistance at the bottom of the stroke, lower the nozzles to their original height (2 1/2 turns down) and perform the drop test again to see if the resistance changes.

[rosaaen89]

11 minutes ago, Mark Maras said:

 Clean everything carefully with lacquer thinner and raise the nozzles to the top (usually up 2 1/2 turns?). Install the domes and pistons without oil and without the shock absorber "jiggly bits". Verify both pistons bottomed out, then lift them slowly to their top positions and let them fall. The stroke of the pistons should be smooth (no resistance) from bottom to top and top to bottom and nearly identical in drop time. If you encounter resistance at the bottom of the stroke, lower the nozzles to their original height (2 1/2 turns down) and perform the drop test again to see if the resistance changes.

if i use pb blaster to lube the exterior of the pistons is that bad ? i cleaned everything with gumout carb cleaner first hand. i cleaned the nozzles as well. i’ll try it all tonight when i get home from work.

[Mark Maras]

No need for lube. The outer diameter of the piston isn't supposed to touch the inside of the dome. The chrome tube in the center of the piston that holds oil should have a bit of oil on the outside.

[Captain Obvious]

That one needle looks like it's seen better days. I don't know if that's contributing to your issues, but it takes a really small change at idle to make a big difference in the idle mixture.

Those dents and other signs of mishandling of that one needle would concern me.

[rosaaen89]

39 minutes ago, Captain Obvious said:

That one needle looks like it's seen better days. I don't know if that's contributing to your issues, but it takes a really small change at idle to make a big difference in the idle mixture.

Those dents and other signs of mishandling of that one needle would concern me.

i also think that needle has been a partial cause to my issues. the front carb looked nice and clean as did the needle, the rear needle looks beat up and inside of the carb/exterior of the piston was black. Also inside the carb almost looks like the piston was coming down awkwardly and making harsher contact on its way down. when i did purchase the car and bring it home both of the carbs were low on damper oil and the rear carbs nozzle was sticking. At the time i had no idea what the part(nozzle) i pushed back up into the carb was. first time working on these, but i’m starting to learn a little bit. 

[rosaaen89]

9 hours ago, Mark Maras said:

 Clean everything carefully with lacquer thinner and raise the nozzles to the top (usually up 2 1/2 turns?). Install the domes and pistons without oil and without the shock absorber "jiggly bits". Verify both pistons bottomed out, then lift them slowly to their top positions and let them fall. The stroke of the pistons should be smooth (no resistance) from bottom to top and top to bottom and nearly identical in drop time. If you encounter resistance at the bottom of the stroke, lower the nozzles to their original height (2 1/2 turns down) and perform the drop test again to see if the resistance changes.

cleaned them out the best i could removed the springs and drained the damper oil. did the drop test both virtually have no resistance and come down at fairly similar times both at 2 1/2 turns up and at the original 2 1/2 down

[Mark Maras]

Great, it would seem the needles, pistons and domes are in good shape. Earlier you mentioned the choke not working on one carb.There are a couple of things that will cause the nozzle to bind up. The fuel hose to the nozzle needs to be ultra flexible. Ztherapy sells silicone hoses. The other problem can be the linkage that pulls the nozzle down and pushes it up. Over time, the flat-bar linkage can warp a bit causing the nozzle to bind up. The carb will have to be removed to check the linkage alignment. Check to see that both ends of the linkage are parallel to their mounting surfaces and lube the outer surface of the nozzles before assembly. Another thing to check is the float levels. The float level is the primary mixture adjustment. You'll definitely need a Uni Syn for balancing the carbs.

[rosaaen89]

49 minutes ago, Mark Maras said:

Great, it would seem the needles, pistons and domes are in good shape. Earlier you mentioned the choke not working on one carb.There are a couple of things that will cause the nozzle to bind up. The fuel hose to the nozzle needs to be ultra flexible. Ztherapy sells silicone hoses. The other problem can be the linkage that pulls the nozzle down and pushes it up. Over time, the flat-bar linkage can warp a bit causing the nozzle to bind up. The carb will have to be removed to check the linkage alignment. Check to see that both ends of the linkage are parallel to their mounting surfaces and lube the outer surface of the nozzles before assembly. Another thing to check is the float levels. The float level is the primary mixture adjustment. You'll definitely need a Uni Syn for balancing the carbs.

i did order some new float bowl to carb lines and throttle return springs from them yesterday. when i was taking the dome off the rear carb it did stick a little and was a little harder to pull off . the front one came off with ease. i’m not sure if that means anything but when it was all tightened up the piston seemed to move fine . i’ll have to attempt to check the linkage. this might be a really dumb question but is the linkage that connects to the nozzle controlled by the choke?

[siteunseen]

I bought these a few years ago from my local dealership. They will have to order them but it seems like they were there in a day or two.

Call the parts department and read off the numbers 16356-25610. They'll punch them in and tell you if they are still available. My guy told me the reason they still carry these was for Nissan forklifts. 

[siteunseen]

Well I missed you on that one!  Got a couple of windows open...

Here's what Mark is talking about I think.