Hey guys new to the forum,
I just bought an 85 k5, I got it home and noticed it had a small gas leak, so I replaced the tank, the problem is it will run but stalls out after hitting the gas for about 20 seconds, the tank is full, one thing i did that i heard might be bad is i started it up to run all the gas out of the lines and I heard that could damage the fuel pump, the pump looks original. I replaced the tank and the sending unit. it also sounds like the carb is sucking air in. this is my first carburated vehicle, and I know nothing aout them, thanks in advance guys for you help.
-Gary

 

As far as the old mechanical pumps go... they either work or they don't. Have you replaced the fuel filter? How bout the brass fuel filter in the carb? The air cleaner is clean and free of debris right? Is this a Quadrajet carb that we are talking about? Did this truck sit for a long time without being started? Also... check the entire length of the fuel line to be sure that there isn't a section of line collapsing as the fuel is sucked through towards the pump.

 

That year model has a return line on the fuel pump. Are you sure you didnt cross over the lines on the sending unit? One only goes down so far into the tank. I had that problem on my camaro when I was messing with it.

 

well to answer your questions honestly, I am not sure what carb it has. The truck ran great before I replaced the tank, and the PO is a good friend of mine and it ran great for him for the past year, no problems. The three gas lines that run up the frame are three different sizes and I marked them and replaced the lines in the same order I removed them, I am really not sure what went wrong. because I let it run for 30 mins to possible let the air out of the new lines, and it didnt stall once, but I drove it around the block and it stalled out again. I will get under and check to see if a line is collapsing like you reccomended, i will also check the fuel filter in the carb. any other ideas would be greatly appreciated.
Thanks
-Gary

 

You can determine your carb, if its a quadrajet, by looking on the driver's side of the carb. It will either say "rochester quadrajet" or "quadrajet by carter". There will also be some numbers stanmped in. You can find the exact carb, mold and rebuild kits for that specific carb HERE. Might try some of the troubleshooting techniques HERE as well. That being said....it is a common mistake to point to the carb adjustments right of the bat as a culprit for unusual engine problems...I'd check the other stuf first.

If you think the carb is "sucking air" I'd check for a vacuum leak. With the engine running spray some carb cleaner around the base of the carb. If it bogs you are sucking air past the gasket between the carb and the intake. If you were working around the carb at all check your hoses, some of them come apart pretty easily. The sticker under the hood on will show the routing for your specific truck.

Ditto on the fuel filters. Be careful with the brass fitting on the carb it scars pretty easily. Running all the fuel out of the lines may have brought some extra gunk to the filters.

When it does run how does it sound? Boggy or smooth?
When you say "get on the throttle" are you just normal accelerating or hard?

 

Can you get it to run by dribbling fuel down into the carb?

 

just normal acceleration, and it was running very smooth before the tank replacement, and when i let it just idle after the tank replacement it runs smooth, when I get it to about 20 mph thats when it stalls out, and I can def hear a air sucking sound, i did not do anything around the carb except remove the air cleaner and filter, but i will check all of your suggestions and let you all know what i find,
thanks again,
-Gary

 

Oh ok, I thought you were having problems with it not wanting to run...

Sure sounds like a fuel supply problem. As stated earlier, replace the filter in the front of the carb and then work from there.

 

thanks for all the help guys, it ended up being a kinked rubber gas line, all fixed and running great, now I am replacing the brake lines, today i replaced the rear wheel cylinders and all the brake lines in the rear, no issues on the brake line job. thanks again.