cranks but no start problem

[zachattack68]

hey guys i have a '68 c20 and today i was driving home and all of a sudden my truck died.when i pulled over i could get it to crank but not strt.it wasn't low on gas because i filled it up right before i left.i noticed it having some sounds like a weak battery when i first started it up but by the second time i tried it fired up just fine.anybody have any ideas?

[litew8]

Maybe your alternator.

[treveiger]

Could be alt an starter, test the battery
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[chevytruckluver]

If it "cranks" (engine spins with the key) you then need fuel and you need spark check for both, just because you put gas in the tank does not mean its getting to the carb.

Welcome to the board from Texas!

[72gmguy]

might be heat soak. Stopping for gas may have caused the high temp in the engine compartment to boil the fuel out of the lines causing vapor lock. Does it start after cooling down?

[69heavychevy]

if everything mentioned above checks out fine, then you might want to also check the ignition module if you have upgraded to HEI.

[zachattack68]

we just recently put in new battery and alt and they have correct voltage.we haven't checked for spark yet but about 30 minutes after sitting it started right back up.but right when it broke down we poured some gas right into the carb and it still wouldn't start.after awhile we could smell gas like it was flooding.wouldn't that men gas is getting to the carb?thanks for the help!

[treveiger]

Do you have a hei or points?
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[zachattack68]

it has hei

[CC69Rat]

Does it have headers on it? Are the tubes close to the solenoid on the starter? Sounds like heat soak (re-starting) / vapor lock (caused the stall) to me.

[this man]

Originally Posted by CC69Rat

Does it have headers on it? Are the tubes close to the solenoid on the starter? Sounds like heat soak (re-starting) / vapor lock (caused the stall) to me.

I'm workin on this truck with him.

No, it just has the standard manifolds. They don't really run very close to the starter/solenoid, and I just changed out the solenoid. I've thought that heat soak might be the reason, but the heat sheilds are still there, and the problem only recently started happening. How can you tell if it's getting vapor locked, and how do you go about fixing it?

[litew8]

Even new parts can be/go bad. But good you double checked.
Ok, you're pretty certain it's getting gas to the carb. If it isn't what CC69Rat says, that leaves electrical.

[CC69Rat]

This is all the opinion of a somewhat 'shade tree' mechanic .. I could be off too, I'm no pro.

Vapor lock from what I know about it, is usually caused when the heat from the engine bay boils the gas into vapor before it reaches the carb. This can happen in several ways but usually it will be an inline fuel filter or something similar. Fuel lines too close to a hot surface such as a header tube or exhaust or just the engine in general.

I understand this concept but personally have never had it happen, .. guys correct me if I am wrong here but if it vapor locks basically it runs out of fuel in that section of the line. The carb runs out of fuel and the engine will die. For the engine to start back up, the temp would need to cool down so the fuel will turn back to liquid form and fill that void in the fuel system.

These type of problems, I lean on the old man. I know what it means, I'm just not sure I'm the best person to talk to about how to fix it.

[don t. - 72gmc]

Originally Posted by CC69Rat

I understand this concept but personally have never had it happen, .. guys correct me if I am wrong here but if it vapor locks basically it runs out of fuel in that section of the line. The carb runs out of fuel and the engine will die. For the engine to start back up, the temp would need to cool down so the fuel will turn back to liquid form and fill that void in the fuel system.

That's the way I understand it as well. I've had it happen on my old ford tractor, but its gravity fed. You wait X minutes, the carb refills, off ya go.

Have fun....don t. ....

[chevytruckluver]

Have you guys had any luck finding the problem yet? What else can you tell us about the history on the truck? has it been sitting for a long time? does it run and drive strong when its cold? its it a quadrajet carb? do you have an external fuel filter?

[litew8]

What does this mean? "recently started happening". That it's been occurring frequently lately? And did you make any changes to the engine/components prior or since?

[this man]

Originally Posted by chevytruckluver

Have you guys had any luck finding the problem yet? What else can you tell us about the history on the truck? has it been sitting for a long time? does it run and drive strong when its cold? its it a quadrajet carb? do you have an external fuel filter?

Well found out one thing, took off my thermostat to see if it was stuck closed, and only the top half of it was there. Went to replace it with the 160* and when i tried to bolt it back in, found that the longer bolt on the dr. side was previously snapped, so waiting on a tap and die set to get it back in currently.

It doesn't sit too much, I usually try to get it out pretty often. It's pretty shady sometimes when its cold but after 3-4 minutes it runs like a champ again. I just upgraded to a quadrajet, it had a 2 bbl on it. This made me think that it was getting heat soaked, I've seen quite a bit about that on here. I have 2 spacers under the quad, and I believe its the material that is supposed to prevent heat soak. it's an internal fuely inside the carb, there isn't one in the lines.

Did a tuneup on it recently, just made it run better, took the plugs out/double checked the gap on it to make sure everything was correct and it was.

[57larry]

pull the dist cap and see if the rotor is turning while cranking. if it's not, you have a broken timimg gear