390 won’t stay running - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 35 (permalink) Old 09-12-2018, 03:37 PM Thread Starter
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390 won’t stay running

1963 Ford 390 won’t stay running. New rebuilt carburetor, starts right up but won’t stay running unless I’m pumping on the gas. Any ideas where to start? I’ve adjusted the fuel air mixture screws, took off the the after market fuel filter and changed fuel lines. Help please! Thanks
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post #2 of 35 (permalink) Old 09-12-2018, 05:04 PM
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Re: 390 won’t stay running

What intake, spacer, carb, distributor, where is the PCV tied in? When it does run, is it smooth? After it dies does it start right up? What is the wet float bowl level? When the engine is cold after a pump of gas how tightly closed is the choke? How did it run before?

Putts drives a 1965 customized Galaxie. Rebuilt 390, 4100 electric choke on a Performer, MX, AC, PS, PB w Scarebird front discs on Cragar 17" S/S.

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post #3 of 35 (permalink) Old 09-12-2018, 07:05 PM Thread Starter
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All original spacer, 4barrel carb, intake and dist. Manuel choke which is disconnected. PCv new. Cranks right up, doesn’t run smooth. Only runs if actively pumping throttle, dies at idle and if I just hold throttle steady. Had it running good and let it sit up for 2 months!!! Lesson learned....
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post #4 of 35 (permalink) Old 09-12-2018, 08:11 PM
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Re: 390 won’t stay running

Check for a vacuum leak.
Hose off somewhere or cracked/rotted, etc.
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post #5 of 35 (permalink) Old 09-13-2018, 09:04 AM
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If it doesn’t run smooth it almost sounds like the timing is off. When I first cranked up my Pontiac after rebuild it was like that. Would run rough and die if you didn’t pedal baby it. I added a proper amount of advance and it ran fine.

Was it ever in time or is this a fresh rebuild? If it was timed well before and this is a new problem make sure the hold down bolt wasn’t loose allowing the distributor to turn.
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post #6 of 35 (permalink) Old 09-13-2018, 02:01 PM Thread Starter
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I had it running well. It was timed good idle. I have tried to reset the timing but it’s so hard to keep it running. What y’all thing about the fuel pump? Maybe letting it sit up messed that up? I’m lost, all vacuum hoses r new.
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post #7 of 35 (permalink) Old 09-13-2018, 02:11 PM
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Re: 390 won’t stay running

If it needs pumping the throttle to keep it running it sounds like a dirty carb. Pumping the throttle gives you a shot of fuel from the accelerator pump, but steady throttle stalls. I think you need to disassemble the carbs and give it a good cleaning. Put the fuel filter back on, too. Will it run at at any steady throttle position? Get someone to run the ignition and look down the carb while you work the throttle with your hand. Watch and see where you have fuel emerging and entering the air stream.

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post #8 of 35 (permalink) Old 09-13-2018, 02:42 PM Thread Starter
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No it will not run at steady throttle
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post #9 of 35 (permalink) Old 09-13-2018, 04:29 PM
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Re: 390 won’t stay running

have a helper start it . push the choke plate towards closed an see if you can get it to run by choking. if you can, - you have a fuel delivery problem. could be float level, dirt in jets, vacuum leak.
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post #10 of 35 (permalink) Old 09-13-2018, 04:47 PM
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Re: 390 won’t stay running

I agree - sounds like a fuel issue. With the throttle open and the engine running, you should see fuel squirt when the throttle is opened and then dribbling out of the boosters once that's over. Can you see fuel vapour coming out of the annular boosters? (the round things on sticks in the middle of the venturi)
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post #11 of 35 (permalink) Old 09-13-2018, 05:41 PM Thread Starter
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So got it running w the choke closed. Once I open the choke it kills. When I pump the gas I see fuel coming out, think I will try to clean the carb.
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post #12 of 35 (permalink) Old 09-13-2018, 07:26 PM
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Re: 390 won’t stay running

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So got it running w the choke closed. Once I open the choke it kills. When I pump the gas I see fuel coming out, think I will try to clean the carb.
This still points to a vacuum leak.
Hoses may be new, but are all vac ports plugged in/hooked to something?
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post #13 of 35 (permalink) Old 09-14-2018, 04:54 AM Thread Starter
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I will run through the vacuum lines and ports one last time make sure I’m not missing any thing before I take down carb.
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post #14 of 35 (permalink) Old 09-14-2018, 04:56 AM Thread Starter
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I will run through the vacuum lines and ports one last time make sure I’m not missing any thing before I take down carb.
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post #15 of 35 (permalink) Old 09-14-2018, 07:30 AM
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1.) If you don't use an original Ford intake the vacuum leak is under the spacer, in the back.
2.) Otherwise, if it idles ok with the choke closed, fix the choke.

Putts drives a 1965 customized Galaxie. Rebuilt 390, 4100 electric choke on a Performer, MX, AC, PS, PB w Scarebird front discs on Cragar 17" S/S.
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