stumble and stalling at idle

So I made my trip down to fl, and now the truck is getting hard starting, and I have to pump the gas pedal to get it started. Once it starts its idling rough but as soon as I give it some gas it smooths out and runs fine. When I get off the gas and it idles it craps out again.

I figure since its only starting and idling proplems that its a fuel issue. The motor is a 352, mechanical fuel pump, 600 cfm edelbrock carb and the rest is all stock. Now would the temp change make that big of a difference in how it idles? I figure when I get back to nc ill clean the carb and re tune with a vac guage.

Any ideas? My one buddy says maybe a weak fuel pump, another says maybe vapor lock. As of right now I'm just guessing, but I just happened in the middle of the trip.

 

Oh yea and I sprayed carb cleaner to check for vac leaks and found none

 

Weak fuel pump would be my guess to. Maybe a small hole in the diaphragm and that's why it is idling rough. Be curious to know what you do find out. Good luck to you.......

 

Nah, when he steps on it, it clears out. Must be gas in the bowl. How about some more info? Engine? Carb? details... I had an edelbrock on a SBM that would do that every once in a while. Turned out to be some piece of trash/dirt floating around in the idle circuit.

EDIT: I'm an idiot...missed the engine/carb up there, haha.

 

Bingo!

 

In my first post I said I have a 352 and a 600 cfm edelbrock and besides that its all stock. I don't know what other details I could give.

I'm guessing its a dirty carb but I won't be back for two more days, then ill tear into it.

 

...I agree- check the idle and transfer ports for dirt. You never know what's at the bottom of fuel storage tanks, and after a fuel delivery it's not settled @ the bottom anymore and becomes a free bonus when you fuel up...

 

Where did you get gas at down here? Some of these places are iffy on quality and if tanks have been cleaned lately

 

Dude I've gotten gas all over from eastern nc, down in atlanta, and then all the way down to gainsville. Stopping every 150 miles for gas and checking oil.

Thanks for the ideas guys, ima order a rebuild kit and give the carb a good cleaning.

 

Try the old trick of placing your hand over the carb while it running, tip open the throttle a little and let it stall, this will draw fuel through the idle circuit and may clear it out.

 

probably

 

Do a compression test.
Had a customer with a '63 352 that wouldn't idle after a long cross-country trip. A compression check revealed low compression on one bank, Removed the rocker cover and loosened the rocker arm shaft hold down bolts 3 turns and re-tested the compression. The cylinders came up from 0-30 psi to 145-165.
Diagnosis, Valve seat recession. Valve job with hardened seats corrected problem.

 

I had this problem with the 750 Edelbrock on my '36. When I pulled the top off the carb and pulled the needle and seat out there was a piece of the needle valve gasket under it preventing the needle from seating. With the throttle cracked it ran anywhere above 2500 RPM but wouldn't idle at all because the fuel pump was pushing fuel right through the carb. Car ran fine when we left home in the morning and like crap when we got home that night.

 

I gotta quit lookin' at them young girls 'cause I just turned 51 on Friday..

 

A remote possibility, but something that happened to me once. The PCV stuck in the open position. and would not idle, high speed OK. take it out of it's holder and shake to see if it rattles. It should rattle.

 

If it was a Holly carb, I would say a stopped up air bleed. Don't know about the Edelbrocks.....do they have a similar air bleed?

 

check the vacuum advance. if it's bad it will give you a leak and wrong timing

 

It could be as simple as needing to adjust the idle air mixture and idle it up a bit, just a thought being as it is only at idle. I'm assuming it runs fine otherwise?

 

Compression before the trip was 120 across the board.

How can I test my vac advance? Before I left I timed it 12 at idle and 38 total I think.

Pvc, this ole girl have the down draft tube still.

I may turn the idle and air screws a bit.

 

I ran into the same problem with my edelbrock carb. I pulled out the needles in the front and blew break cleaner through them, that helped a little. I rebuilt the carb, that helped a little more. I replaced it with a Holley and the problem was fixed. I just bumped up the idle a bit so I wouldnt have to worry about stalling out at lights and such. Let me know if you get it running right. I have had this happen with a couple of edelbrocks and they never worked quite right again even after a reubuild.