235 wont start second time

[Virginian]

Hello all, have a 55 chevy truck with a 235 rochester carb pretty much original except for alternator update, if I try to start it for the first time of the day it will fire up, If it runs for 10 mins or more and I shut it off it will NOT restart, I have to let it sit a couple hours then it will start with a little cranking, cool day out today, no restart, tried different timing, checked float level, accelerator pump etc. Any one have ideas ? By the way it cranks normal speed because I jump it off another car to have juice to crank it.

[dsraven]

pull a spark plug and check the colour and also for spark.maybe the carb float is allowing the carb to overflow after shut down so it floods the engine.

[OrrieG]

Originally Posted by Virginian

By the way it cranks normal speed because I jump it off another car to have juice to crank it.

Get a good battery to start with, if you are jumping it to start every time the battery may not be providing enough power to fire the coil and points. Also, all the jumping may have damaged the alternator (assuming that is what it has and not a generator) so it will not charge or provide power to run the engine.

Not starting when hot can be vapor lock or possible bad coil, or as mentioned carb boiling over and flooding. Accelerator pump in the rochester may be bad too, not giving you a shot at start. The pump piston is notorious for having to be replaced if it sits for too long or every 4-5 years even under daily use (when I ran one I always carried a spare kit).

[dsraven]

when it won't start, pull a plug and check to see if the plug is dry or wet, and if there is a good blue spark. if wet it is possibly the carb float overflilling the carb and flooding the engine, if dry then maybe the fuel is draining from the carb after shut down. a poor or no spark could be due to the no battery thing where the coil is not seeing a good voltage.
-if the plugs get wet all the time from a flooding carb they will cause erratic running as well, compounded by a possible poor spark. the plug porcelain absorbs the fuel and causes a ground track.
-one thing that I have done in the past is install a clear fuel filter up near the carb so I can see if the fuel is running back to the tank. if, after running and a shut down like when it won't start for you, the filter is empty then the fuel pump valves may be to blame for allowing the drain back. there is a siphon effect that can drain the float bowl. that would explain the time to crank before it starts. the spark plugs would be dry in this case. the pump has to bring fuel all the way from the lowest point, or the tank, back up the the carb so it takes a bit before the engine sees fuel and starts.
-if it is a float problem where the float inlet valve is allowing the residual system pressure to overfill the carb then the plugs will be wet after you attempt to start. a float that is set too high or an inlet valve that is leaky can be masked when the engine is running, as long as it isn't leaking too much, because the engine will just run rich but after shut down the overfull carb will drain the overage fuel down the throat of the carb into the engine. this will make the engine hard to start if attempted too soon after the last shut down because the engine is flooded. the fuel has not had enough time to drain out past the pistons or evaporate. if this is the trouble remember the fuel is also diluting the engine oil and the oil may even smell like gas. this effect can virtually blow the oil pan and valve covers off, or distort them, when the engine is cranked and the extra fuel ignites inside the engine.
-if you crank and the engine won't start so you pull a plug and it is dry, the problem could be the drain back issue mentioned earlier. you may have a fuel pump problem where the valving is allowing the fuel to go back to tank. the siphon effect can drain the float bowl so it takes a long time to fill the carb.
-if you don't have a good blue spark then you mayhave a points/condensor/coil issue etc.

hope it helps. at least a starting point.

[mr48chev]

Won't fire up while cranking when warmed up or won't spin fast enough to start without jumper cables?

I you would clarify exactly what is happening and we can probably come up with suggestions that will actually help fix = the better description of what is happening or not happening gives us a lot better idea of what the problem actually could be.

[Virginian]

Battery is good,spins engine fast enough when warm it's just getting depleted after several minutes of cranking I only jump it then, if I am trying to trouble shoot, I will check plug condition if wet or dry today, new complete distributor was installed, but it had this issue before that.

[1project2many]

Since we never know on a forum, are you used to driving carburetor vehicles? You're not pumping the gas before starting when warm, right? Can also try holding foot to floor while cranking. Helps if carb bowl leaks slightly or if fuel is vaporizing while engine is off. If the engine begins to start you'd better let off dang quick...

[Virginian]

I have had at least 8 carbureted vehicles in the past. Plugs were black and sooty but not wet, would not start tonight at all, ran out of daylight will check spark tomorrow when I have an assistant, carb was rebuilt not long ago , but had real bad leak running down inside carb throat, but I pretty much got that stopped, I Will check out everything ignition wise and post back.

[dsraven]

grab he carb off and make sure the float doesn't have a pin hole or something and that the level is correct. aso check the inlet valve with a few pounds of pressure against it to see if it leaks past and could overflow the carb when you shut the engine off.
for spark, you can make a quick spark checker out of extra stuff in the garage. just google home made spark tester for ideas. it is even easier if you have a couple of old plug wires kicking around for parts.

[dsraven]

if the plugs are black and sooty you can clean them and try again until you get things sorted out. I recommend replacing them when you get it figured out and no more issues. sooty plugs will cause misfire or no start because the carbon (soot) is a good ground track instead of going across the plug gap.

[mr48chev]

Is it hard to start after you run down to the store or place that ten minutes away and then come out and try to start it or does it quit after about ten minutes and won't start?

If it's the first I'd think that maybe it is flooding after you shut it off. If it is the second scenario I'd take a look at my gas cap and make sure it's vented. I had a heck of a time with what were supposed to be vented gas caps a number of years ago and after three different caps got one that was actually vented. If it quits after about 10 minutes of running get out and carefully open the gas cap and see if you hear air rush in and the sides of the tank pop back out after being sucked in. Note: the less gas in tank the more air you have to create the vacuum with and the more gas in the tank the time the vacuum in the tank overtakes the suction of the fuel pump will be a lot shorter.

The car I was fighting that on (51 Mercury) quit at the same spot on the way to work two mornings in a row until I got it straightened out. First morning I walked a mile to a gas station and got gas and walked back and put the gas in and it started. Second morning it quit and I was ready with a jug of gas in the trunk and the tank went foomp when I opened the cap. Third morning it quit with a second new cap.

[Virginian]

I figured out the problem, something wrong with the way the ignition switch is wired or bad Switch, don't think the ballast resistor bypass is working
I have to keep the key turned all the way over to the start position, I did not do that in the past I have a foot pedal Start.no voltage to the resistor when key is just in the on position it starts right up cold or hot if I hold key all the way over and push foot start, don't really know what happened or why heat was a factor, but I will trouble shoot some more, thanks to you all.

[Virginian]

Ok, someone installed a key start type switch and wired it for key start, I have a foot pedal start, the switch on the starter stopped working, thus no 12 volts to coil for starting also contact in key switch is intermittent that supplies 12 volts to the resistor so It was hit and miss on starting, but I still think it was trying to start on only 6 volts to the coil, and that was not working with warm engine. Working on getting it wired correctly now.

[OrrieG]

Years ago the trick with 6V VW's was to use a GM horn relay because they had the same issue with the starting circuit going all the way to the front of the van and back. Got to love old owner upgrades.