My 73 240z (with round top carbs) started and ran fine about 3 months ago. I went to move it out of the garage and it ran real rough. I got it back in the garage and now I can get it started with starting fluid, but I dies as soon as that’s exhausted. After that I can get it to almost start.

I read thru some of the posts and it seems the problem might be fuel related so I took the top of the floats, there was gas in the bowl, cleaned the little filter and reassembled. I also bought a new inline fuel filter and added oil to the plunger in the carb. I am next going to try blowing air through the fuel lines. Any suggestions will be greatly appreciated.

How old is the fuel? Sitting 3 months shouldn't be a problem but if you last filled it up 6 months before that it might be.

That’s as good as place as any to start. I can hook up a bi-pass at the fuel pump.

Have someone sit in the car and pull the choke full on - then off - then on. You stand at the engine and see of the action at the carb's matches the action at the choke handle.. It sounds like your chokes may be hanging up... for one thing. Also check that the vacuum slides are freely moving...

Pull a couple of plugs - say #1 and #6 and see if you fouled them that last time you moved the car. Cold weather starts in the old Z's require very rich mixtures - starting a car and moving it - where it never reaches full operational temp's - can easily result in fouled plugs..

just some thoughts...

FWIW,

Carl B.

Ok, here is what I have so far.

I disconnected the fuel line at the pump and carbs and blew air from my compressor thru them.

I also bi-passed the tank, disconnected the fuel line and ran the fuel line from a quart jar. No difference, it ran for a bit off the starting fluid and died. Also interesting there was less gas in the quart jar so I believe that it’s getting into the engine.

Had my son pull the choke leaver, it appears to function correctly.

Because it starts with the starting fluid I assume the plugs are good, but I will still check them. I am also thinking about the coil not providing enough spark or perhaps the timing?

Might be the fuel pump. If you have not changed it, might be good to do anyway.

Could also be that the arm of the fuel pump which rides on the camshaft is stuck.

Don't assume the plugs are good. Take Carl's advice and check them out. It's easy enough to do, and will tell a lot about what is/is not going on. Please let us know what the plugs look like when you get in there. Just curious, when were they last changed, and what are they gaped at?

Here is an update. The plugs had a lot of carbon on them so I replaced them and checked for spark, they were good. bty the gap was .35 . I put the new onesi in and didn’t make any difference. So… by process of elimination I am going to tear the carbs apart and clean them. I got the DVD from Z-therapy so I have good instructions now.

IT RUNS!

Ok here is what I did. After cleaning the carb and it still not starting, I found out after an extensive search on the forums that I have a secondary fuel pump at the tank. Apparently it’s a dealer-installed item to prevent vapor lock. I bought a metal fuel filter and by-passed the pump entirely. I then disconnected each fuel line and took my air compressor and blew air through each line to ensure it was clean. I also drained the carburetor bowl and blew air through it. I believe I had a blockage in the line between the tank and the pump.

Thanks everyone for your help.

So I did some additional tweaking this weekend and it’s running really good now. I figured I would share incase someone else has a similar problem.

Re-watched the Z-Therapy video and caught a bit that I had missed before. I have always had a lot of trouble getting the carbs to run right, really hard cold starts. Above the throttle linkage there is (what Z-Therapy calls) a maintenance adjustment screw for the throttle position. I backed this all the way out (like the video says) and was able to finally adjust the carbs correctly. The PO had used it like an idle screw so the actual idle screw on the carbs was always off.