240z (barely) runs very unevenly!

[siteunseen]

Try pushing a WD-40 straw down the overflow bung to see if the float is stuck. You should be able to push down then see the straw rise back up slowly.

The fuel valve could be stuck open letting fuel continuously flow through. Good luck!

[Mark Maras]

 The WD-40 straw is a great idea. I'd also pull the float cover, inspect the needle valve for foreign matter holding it open, float and float pivot to find the reason for the excess fuel.

[Bettan_85]

Thanks siteunseen and Mark! I managed to stop it from pouring out by cleaning everything inside the float chamber. 
however, it still runs terribly bad... sort of Coughs itself forward :/.

any Other suggestions?

thanks!!!

 

[siteunseen]

What type stuff was inside the float chamber? I've cleaned two gas tanks so far, my 240 was the worst by far.

That's not rust either, just crud. I don't know your story but if you cranked it over when you first bought it like I did that stuff gets all in your fuel system.

Edited August 26, 2020 by siteunseen

[Mark Maras]

 Coughing from the carbs or tail pipe? I'm thinking it may be running lean. Is it possible that you changed the float setting when it was pushed with the straw? Also, did you remove or inspect the needle valve for crud?At this point, I'd pull both float chamber tops and compare the fuel levels.

[Zed Head]

On 8/25/2020 at 12:43 PM, Bettan_85 said:

it sort of looses all power/fuel (?) pressure, the Roms drop and then milliseconds later picks up again. 

I suspect the issue arose after I left the car outside during a Rainy night, however that might just conincide with the issue...

Anyhow, first it just dropped power a couple of Times during a 30 min drive, but since then it has only been worse, and now I can barely drive it. And then it works fine for a couple of minutes, then back to worse. 

Anyone with a clue where to start? I quite recently (been driving 20h plus since) changed the spark plugs, condenser, distributor rotor, point set, fuel filter. 
 

Gave engine a tuneup.

Put at least 20 hours on it afterward, no problems.

Car was outside during rain.

Engine started running poorly, sporadically, now runs poorly, consistently.

 

Odds aren't bad that something came loose and slowly slipped out of adjustment.  I'd recheck the points gap.  The lock-down screw might have loosened.  There is pretty good force on the points as they open.  If they slip, the gap will close and you'll get poor spark.  Could also be that the distributor has turned if its lock-down screw was loose.  Check timing.

SteveJ suggested the same with his gap and dwell suggestion, to verify.  Then tried again with the dwell meter question.  But since you never answered he moved on.

Easier to check than fuel too.

[ConchZ]

The fuel pouring out of the overflow on the float bowl is a big clue that you've got a float valve problem, and it's stuck open now, but it could also stick shut.  This worked for me once.  Use the back end of the screw driver to whack the float bowl to see if you can jar it loose for at least long enough to get you home, then take off the float bowl covers and clean it up/out.

If you're having problems with the float valve, that's the place to start for your drivability issue.    I've had mine stick open and stick shut.  Either way will cause the car to buck and hiccup.  You gotta clean them up and reset the float levels once you are done.  You could spray carb cleaner down and around the valve and work it to see if you can loosen it up.  Blow through the inlet on the top of the bowl to verify the valve is opening and closing appropriately.  

Next place to check is the choke cables.  Are they still set right, or did one of them come loose,, leaving the nozzle too far down/up.  Sounds weird, but it's happened to me.  After the above, recheck your timing, then take if for a ride.  If you still have problems, go after the ignition components.