The Stovebolt Site Forums The Shop Area Engine Shop Hard starting question

Hey fellow bolters, what is the most logical reason why an engine won't start when it's been left over night or longer? My '72 GMC with 402 is very hard to start first thing. It will generally fire once and then not fire again until considerable cranking is done. Almost like gas starved, but don't know if that is the problem. Once it has been started, it will fire right off first try every time for the rest of the day or so. Also doesn't miss, die, choke or anything else once it has been started. I installed new plugs and wires, but no other tuneup stuff has been done since I brought her home a few weeks ago. No difference in the hard starting before or after the plug and wire change. Started just as hard in Wyoming as it does now here in Oregon, so don't think altitude has made any difference. I haven't changed points yet and the vacuum lines all seem to be in good shape and tight. Carb is a Rochester Quadrajet. I know it sat for quite a while at my dad's, so maybe jets are gummed in the carb, though I would think if that was the case, it would start hard all the time. Don't know much about carbs though. Sure would welcome some suggestions as to what might be causing the problem. Thanks.

Big V8s usually start easily even when cold. If it has an automatic choke I think your auto choke is not closing enough in some types
of weather. Are the no-start days during the same kind of weather? Some days are not quite cold enough to close the auto choke completely. Most chokes need to be completely closed on the first start even in warm weather.

Before your first start in the morning don't turn the key to start, push the accelerator pedal to the floor,release it, go out and remove the air cleaner, check to see if the choke plate is closed. If not closed, hold the throttle open at the carb, push the choke plate closed, release the throttle, go back inside and turn the key to start. If it starts you have found the problem. It is either hanging on something or needs adjusting. Auto chokes usually need to be adjusted for different conditions.

Another possibility is a bad condenser. This exact thing happened on my 225 slant six but it was hard to start every time if it was allowed to sit for more than an hour.

Overnight your quadrajet bowl is draining out. it takes a few cranks to get it to fill back up. Common with older quads. They sometimes, when rebuilt by a good carb man, will quit doing that.............

I think the bowl is draining out over night. Most of the old Q-jets leak some from the secondary ports. If you take the base off the carb and flip it over so you are looking at the bottom of the center section, you will see two plugs at a slight angle in the middle of the carb. That where they leak from. We have good luck cleaning the area real well the using JB Weld on them. Just coat the whole area, but note that the base plate must still clear. Some of the rebuild kits had a wedge shaped black sponge that was suppose to help the problem, it never really worked. Just try the JB and see if it don't help. You don't even have to get inside the carb. It just takes a few screws from top and bottom. Joe

Check and adjust your automatic choke. Like gusc said check to see if it is closing all the way when it is cold. The little spring under the little heat box on the manifold next to the right side of the carb may need a new spring.

I overhauled the Q-jet on my wifes Olds 403 and never had a leaking problem, but it is good info to store in the ole brain. I'm not the best carb guy around either, once reversed the main gasket on my 292 one ton, backfired like crazy.

Never had a bit of problem with the Q-jet, just o/h it because I was replacing the manifold valley and it was handy. Always liked the different size barrels for economy.