Why didn't it start?

[mud390]

Ok. Here's what happened. 1981 K10 with a 250 inline 6, speed manual. Cranked the truck up at the house, feed it just a little gas like always and it started right up. Let it warm up for about 10 minutes and off I went to the gas station to put some air in the tires. I need an air compressor, but thats another topic.
Anyhow. Get there, shut the truck off, put air in the tires. BS with the guys that work there for a few and back in the truck. It was off for no more than 10 minutes. Try to start it and it just keeps turning over. Feed it a little gas. Nothing. Pump the pedal a couple times. Nothing. Pulled the air cleaner to see if it was getting gas and there was steam coming from the carb. Granted it is about 35 to 40 degrees outside. Tried to start it a few more times, with no luck. Left the truck.
Came back about an hour later. Cranked on it for about 20 seconds, feeding it gas, and it very stubbornly started. Once it was running, it ran fine. Got it back to the house, about 2 miles, with no problems. Shut it off, and started it up 3 more times without a hitch. What gives???? Don't want the truck to leave me stranded again.

Kris

 

[hunterguy86]

Vapor lock?

 

[lak2004]

Thats happened to me a couple of times and I havent figured it out yet, what carb do you have? Choke working right? Flooding it? Mine has left me stranded on top of a mountain pass in a single digit temp snow storm

 

[mud390]

I was thinking vapor lock too. Not 100% sure.

The carb is the factory 2 barrel. I would guess no bigger than 500cfm. I'm pretty sure it wasn't flooded. I could smell gas, but it wasn't overwhelming. Choke works fine. I went outside today and started the truck, and it started just fine. Weather was about the same. Let it run for 5 minutes, shut it off. It sat for 10 minutes, cranked right back up, no problems. I'm baffled. A fluke maybe??

Kris

 

[Burbdood 74]

This is just a shot in the dark, but it could be your carb icing up on you. I've had the same thing happen to me, and if you don't have the heat riser tube hooked up, condensation may be forming on and inside the carb and icing it all up. Like I said, just a thought.

 

[mud390]

Icing? Never heard of that. Is that the gas icing, or just ambient moisture icing? The air cleaner has the line from the valve cover running to it. Is that what you are talking about?

Kris

 

[lak2004]

This is just a shot in the dark, but it could be your carb icing up on you. I've had the same thing happen to me, and if you don't have the heat riser tube hooked up, condensation may be forming on and inside the carb and icing it all up. Like I said, just a thought.

Interesting thought, next time it happens to me Ill have to check that out. Could explain why it runs crappy after as well, the water getting into the fuel. Time to keep some starting fluid in the console.

 

[Dabba]

what is this vapor lock?

i r nub

 

[lak2004]

vapor lock only happens when it is hot AFAIK, it is when fuel vaporizes

 

[Dabba]

oh yeah okay i heard of that before

 

[noJeepshere]

my 81 now has a 350, but i swapped out the 250 (kinda wish i kept it) before i did, the rig would do that alot in the cold winter weather of eastern washington. i found out that it was water in the tank that came down the line and would freeze. several bottles of gas line antifreeze cured the prob.

 

[Burbdood 74]

Icing? Never heard of that. Is that the gas icing, or just ambient moisture icing? The air cleaner has the line from the valve cover running to it. Is that what you are talking about?

Kris

When the carb is cold and then heats up, condensation can build up inside and combine that with water in the gas and lower air temps, and ice can form in your fuel lines and in your carburetor. then gas won't flow through the jets. The Edelbrock on my 72 Ventura II does this all the time. It always runs like poo in the winter.

The heat riser tube is the tube that runs from the exhaust manifold to your air cleaner and feeds warm air to your carb when the engine is running. If you have an open air filter with no heat riser tube, (like I do on my Ventura II), then the problem is worse than if you had the heat tube.