Duster quits on curb idle

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7

73 Plymouth Duster

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Hey guys so I'm having some fuel issues, at least that's what it seams like by the way it dies. Definitely not electrical.

So the car will run fine in park or neutral but in drive after driving a little while it would die if you weren't moving and in gear. It drives just fine if you were moving but at a light it would die if I didn't nurse it with the gas pedal or put it in neutral.

Initially we thought it was vapor locking in the lines but when it did it on a cold day we thought it could be carb ice (since I have a ram air hood scoop and big air filter) but I can't find any ice and it will still quit on a HOT day. Finally we suspected a sticking float and one day when it quit I pulled the side screw and fuel dumped out, so i bought a new valve and seat and I thought it fixed it for a while. However it'll stick so im at a loss to where to check next...
 
you are having the same issue?

oh and my last sentence doesn't make a lot of sense. I meant to say i changed the valve and seat and it seemed to fix it for a little bit but the car will still die just like always. When it does I hop out and check my side screw levels and they are perfect (just a tiny bit of fuel seems out)
 
Yeah, I'm hoping it may carb tuning, mine idles decent in park and neutral, but under load it wants to die if its not in motion. I haven't had time to get down and dirty with a new born baby. It's hard.
 
What do each of your plugs look like?
Not even after it quits, just right now.

You could literally have opposite problems and the same symptoms, and a plug would tell us a starting point.
 
Here is one of the plugs, mildly black around the ring but other than that I see no big issue with them, maybe you do?
 

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I would set the timing first. Then set carb mixture screws to highest rpm/vacuum . Then set idle.
 
Any fuel dripping in from the boosters? That shouldn't happen.

Make sure the float level is correct and there isn't any dirt in the carb.

The plugs look fat as heck.

Check oil dipstick for fuel smell. If it's fuel saturated, I'd change it.

Set timing first! Not know what you have for an engine, I'd start anywhere from 12-16 BTDC for idle timing. If it starts OK when hot, you're still ok in that range. Then adjust the carb settings.
 
Don't know what's in your motor but with bigger cams I've had good luck opening the mixture screws a quarter turn at a time from highest vacuum setting until it idles good in gear. Did you check for any small vacuum leaks? Bigger cams like a richer idle because the low vacuum cant pull a lot of fuel. I agree with crackedback, more initial timing will also help. Just watch your total advance. More motor info would be helpful. Good luck
 
thanks guys, got some advice from some friends to also advance the timing.
It's a 318 with a dual plane high rise intake, holley 650, headers, big 2.02 intake valves, and a lumpy cam so i know I already have low vacuum and i'm still checkin around for leaks. The timing is around 12 right now I think, gonna set it to 15 tomorrow.

float levels are perfect.

Oh another little update, today on the way home I discovered it will now die in neutral. (it was 90 degrees too)
 
So by the advice of a close hot rod friend I replaced the power valve. He said if it had ruptured then it would constantly suck in more fuel instead of holding vacuum and flood the engine, seemed like it would work but sadly it didn't.

Eventually I will mess with the timing but at this point it runs so well I don't want to re-time and reset the mixture settings. I am pretty much convinced it is a carburetor problem or a vacuum leak (I have tried driving around with my interior vent system and vacuum advanced plugged off and nothing changed.)

So I guess I am asking if there are any more ideas on possible carburetor problems or common vacuum leaks?
 
Lumpy cam, set it at 20* timing at idle. You're going to have to mess with the mechanical advance in the distributor so your total isn't out of bounds.

Put as much initial advance on it that it will take and not kick back on the starter when hot.

Put a power valve plug in it to set idle so the "it's the power valve opening" will get sorted out. If the mixture screws kill it at idle, on the idle circuit, the PV is not open/flooding the engine.
 
I found my mopars like the fuel below the sight hole. Worth a shot and it won't cost a dime to try it.
 
Doesn't hurt to try both at this point. Ill try as much advance as I get and reset my mixture. So you think I will have to mess with my distributer to make sure it doesn't over advance at high rpms? How will I know if I am out of those bounds? it wont run?
 
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