Fuel system not staying primed

thejoe

Member
Jul 7, 2020
28
6
13
Moscow, ID
Last weekend I had to remove the slave cylinder since it was leaking really badly. When I jacked the car up, I lifted the front first and then the rear, front was higher than the rear. I tried to start it to let someone hear how it sounded while it was on jackstands and it would turn over fine, sounded strong, but didn't catch at all and didn't start. She had been sitting for 3 days since the last drive which went fine. I got the slave done, got her off the stands, and would turn over but wouldn't fire. I primed the carb (Edelbrock 4 barrel) through the bowl vent tubes and she started no problem and ran great - plenty of power, no hesitations - for about 15 minutes as I drove around. I tried parking in the driveway with the nose down to avoid letting the fuel line drain (I thought that's what happened). This morning, she turned over fine and caught once like she was going to start but then just cranked without ignition. It seems to me that the fuel system is not staying primed. I don't see or smell dribbles of gas. The mechanical pump on my 302 is new. I haven't been able to check the fuel line from the tank to the hard line yet. Any other ideas?
 
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Last weekend I had to remove the slave cylinder since it was leaking really badly. When I jacked the car up, I lifted the front first and then the rear, front was higher than the rear. I tried to start it to let someone hear how it sounded while it was on jackstands and it would turn over fine, sounded strong, but didn't catch at all and didn't start. She had been sitting for 3 days since the last drive which went fine. I got the slave done, got her off the stands, and would turn over but wouldn't fire. I primed the carb (Edelbrock 4 barrel) through the bowl vent tubes and she started no problem and ran great - plenty of power, no hesitations - for about 15 minutes as I drove around. I tried parking in the driveway with the nose down to avoid letting the fuel line drain (I thought that's what happened). This morning, she turned over fine and caught once like she was going to start but then just cranked without ignition. It seems to me that the fuel system is not staying primed. I don't see or smell dribbles of gas. The mechanical pump on my 302 is new. I haven't been able to check the fuel line from the tank to the hard line yet. Any other ideas?
Edelbrock's carburetors are prone to the fuel evaporating out of the carburetor if they sit for more than a day or so thanks to the wonders of modern gasoline. Switching to 100% ethanol-free fuel will help.
 
That would make it turn over and over and over without starting? I am wondering if my float bowls are filling up enough. Maybe I just need to get it out for a good long drive?
Yes, I used to have the same issue with my Edelbrock Thunder AVS carb. I replaced it with an EFI system (MSD Atomic), that I'm ultimately unhappy with for other reasons, and will be putting the Edelbrock back, using an electric pump setup that will allow it to self-prime every time.

Uncle Tony on Youtube has a good explanation of what's happening. I didn't realize this was the cause of my problems five years ago when I made the switch to EFI. Now that I understand the problem, I know how to fix it. You can do so by either using a bottle of fuel to fill the bowls, or you can use an electric fuel pump setup that'll prime it on key-on.




View: https://www.youtube.com/watch?v=1WNpdy9-zdE

I can't take full credit for the idea to run an electric pump, that came from @extra_stout :
You can run carburator with a return-less, low-pressure fuel pump. There is a solenoid witch keeps the pump only running when the engine runs AND it will prime the pump for some seconds, when you put the key to "ignition on". You can also jumper this solenoid by an additional switch that you can prime "by hand".
 
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I got home and on a whim decided to try and start her and she started right up. She started right up this morning and drove 10 miles to work without issues. So, maybe parking nose down has helped? I'm not entirely sure. I didn't have time to watch the video yesterday, but I'll get to it.

Any other thoughts from the collective wisdom of the forum?