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Bettan_85

240z (barely) runs very unevenly!

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Hi, I almost didn’t make it all the way home today since my 240z -73, 5 spd, now runs terribly bad! ? 

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

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. 
 

Super thankful for all input, been planning a road trip with some friends this Friday ?..

Thanks! 

 

 

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Is this the first time the car has acted this way? Did you verify the gap and dwell on the points? Does it only happen under load?

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I would try replacing the condenser with one of you old ones if you still have it, I just went though three new ones that I bought from rockauto and all three failed. I am back to using one of my old ones with no problem.

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It’s the first time it acts like this! Just started a couple of days ago. 
It happens both under load and during idle., however was more noticable at higher rpms First.

yes, I checked the gap on the points at least. And! They’ve been working like a charm for 20 hours (at least).

any ideas? ? 

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You should put your videos on youtube.  They won't play for many people.

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Yes, they all seemed to work at first, I do not recall how long the first two lasted, a couple of weeks maybe? they would start causing the car to run very rough and backfire, the timing gets messed up. The last one went for about 150 km and then started doing the following, it would be running well and just shut off like the key was turn off, it restarted every time for a while and I thought I had a loose wire, and then completely died. Swapping out it with an old one worked. If you do not have the old one try using the one that is on the coil as I am sure it is just for noise suppression for the radio. 

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 I'm leaning (snort) to a fuel problem. I've experienced similar symptoms and found them to be water related. If you have any clear fuel filters, check those for water. I'd also pull a float chamber top to see if there is water in the bottom of the bowl(s).

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Thanks for all the suggestions!! I will check if I find any water in the float chambers and also the fuel filters.. Then move on to ignition... ? hopefully I can get it to work.. 

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Ok, this is bad. One carburator is actually leaking/spitting out gasoline the wrong way, though the air intake. Next step remove and clean the carb? The float misfunctioning? Other ideas??

 

thanks!

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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!

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 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.

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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!!!

 

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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.

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Edited by siteunseen

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 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.

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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.

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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.  

 

 

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