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Trouble Getting '73 Hybrid Starting and Running


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Hi, I'm fairly new to this forum and the world of Z's, but I'm hoping for some advice on what to attempt next.

 

I picked up a '73 240z with a large list of modifications, including the dual weber Hitachi SU carbs from a '72, and a "fresh built" l28 engine and head. I've done a small set of fixes and minor modifications to get it running, but as of yet have only had momentary success, and I have a suspicion that the electrical is to blame for the behavior. I've got a Pertronix electric points system installed, with the flamethrower coil that accomponies it, and have confirmed I'm getting a spark. I just replaced the old fuel pump and have it measured at about 3.5psi, checked for any obvious vacuum leaks, put new gaskets on the floater bowls on the carbs, and played with the timing to see if that was the issue, but no luck.

 

I've managed to get it started and idling, but only once, and after no changes, it refuses to run again for more than a few seconds. I've tried with and without the ballast resistor, and am going to try some new plugs today, but I just can't seem to pinpoint the issue.

 

Are there any obvious fixes I'm looking over that could be suggested, or common problems I might have looked over? I desperately want to get this beautiful old car back on the road, and would hugely appreciate any and all suggestions. Let me know what information/pics I can provide to help, and thank you in advance.

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It's ok just wanted to know if still stock carbs.

 

Fuel level in the SUs is critical to proper operation. Also are the choke cables connected and operating?

 

Here's a site for troubleshooting...  http://www.311s.org/su-setup/su-setup.html It's not for the L24 but gets you started.

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Thanks for the link, I'll read through that!

 

The choke cables are connected and operational, and if it makes any difference, the carbs are the stock 72 carbs, but the previous owner put in an l28 engine from a 280, and put the carbs on himself, so I'm not sure what to check as far as how well he did that.

 

Putting new spark plugs in definitely help thankfully, and it starts pretty consistently now, but putting the accelerator down at all still causes quite a lot of coughing. Fuel pressure gauge is reading about 3.2 psi right before the carbs, which I've read is about what's recommended. I'm going to adjust the timing the best I can now that it actually starts and idles most of the time, and see how big of a difference that makes as well.

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The small black plastic tops unscrew and lift out. Inside is oil filled. This oil acts like a shock absorber and prevents the slide from opening to fast and the engine from suddenly going lean. It's the carb equivalent of an accelerator pump. You'll have to research what weight and quantity of oil to use. I think around 20W, some use ATF. 

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