denf221

Hey everyone have a 72 supreme stock 350. If the car sits for awhile it will crank for long time before starting,however if I put little gas in carb it starts right up, I can drive it park it for several minutes,starts right up but once it sits for day or so I have to put gas in carb again for quick start,what does this sound like?

Oldsmaniac

This sounds like a normal problem due to evaporation of the fuel in the carb bowl. It also could be the casting plugs leaking in the carb. I assume it is a 4bbl quadrajet carb? You could also try a paper fuel filter with check valve if the filter is stock. After sitting remove the air cleaner and look inside the carb while manually working the throttle. You should see the 2 jets of fuel squirting as you work the throttle. If not the carb is dry. Also make sure your choke is working properly.

Quadrajet Power

Several possibilities. This is common on carbureted engines.

What type of carburetor do you have?

Today's fuel with ethanol evaporates quicker that 70's fuel. Most float bowls are small, and if float level is low, fuel can evaporate quickly below the accelerator pump feed.
Some early carburetor have fuel wells that will leak and if not repaired, fuel can leak from bowl while sitting!

So, recap possibilities
1. Low float level
2. Fuel wells leaking
3. Accelerator pump failure
4. Normal fuel evaporation
5. Fuel flow back to fuel pump

Possible fixes
1. Set float level a little higher
2. Seal fuel wells
3. Replace accelerator pump
4. Use fuel check valve to prevent back flow
5. If Quadrajet, you could Chang to non windowed needle/seat
My favorite solution, drive it more often!

Hope this helps.

blakes7

What if it's as simple as the paper fuel filter with the rubber check valve, installed backwards? I have the same problem, and have yet to get my lazy self out there and try reversing it. The winter here has a lot to do with that.

MDchanic

They all do that.

- Eric

D. Yaros

Hmm, have never heard of this? Anybody used it and found that it solves the "long start due to fuel evaporation" problem? Does this filter go in the glass fuel bowl?

denf221

Thanks all recovering from surgery have to wait while to look at it. Yes it is original carb so I believe it is quadrajet