bad gas in fuel lines?

[chuksk20]

Hey guys, first time posting. My 86 k20 has dual tanks, the guy I bought it from told me they never used drivers side tank, and my passenger side started leaking. Me, being extremely foolish, started the truck to try and see if the truck would switch to the other tank. Long story short, before I could switch it over to the passenger side tank again, I think I sucked up some bad gas into the fuel lines. Truck died within a couple minutes. If I pour gas directly into carb, it starts right up. So, is bad gas a possibility? And if so, what's the easiest way to flush lines? I thought perhaps pouring gas into carb with the line removed from carb, so the mechanical fuel pump can do the work for me. The fuel filter is good, and I see this as the easiest solution, but do I risk damaging anything from the old and possibly dirty gas?

 

[chengny]

Get a can of ether (starting fluid) and use that to keep it running until the bad gas is purged.

Remove the air cleaner and shoot a good blast of ether down the throat. Crank it over. Once it fires, keep it running by giving it light shots of ether - always trying to make it run on the gas. There is probably about a cup of gas in the line from the tank transfer valve to the carb inlet (and another few ounces in the carb bowl) , so it shouldn't take to long to burn off the contaminated gas.

Another way is to disconnect the fuel line at the carburetor inlet, attach one end of a hose to the gas line (lead the other end away from the motor to eliminate the chance of a fire) and crank the engine. Just a few full revolutions (2-3) of the engine will be enough to pump out all the bad gas and pull in good gas. You will still have to deal with what is in the carb bowl.

If you decide to pull the inlet line, be sure to use two wrenches (as shown) - that will prevent you from twisting the tubing.

 

[chuksk20]

So, I have an inline fuel filter, I replaced it with a clear one. I put gas in the carb to start in, had it running for about 90 seconds on and off constantly pouring in gas. No fuel ever made it to the filter. I'm thinking the tank switch is stuck, or I gunked up the fuel pump? Can I bypass the tank selector?

 

[1987 GMC Jimmy]

You could take the rubber line off the fuel pump and blow into it. If you feel like you're moving air and you can hear bubbles in the tank you want selected, that's not the problem, and I'd replace the fuel pump. If there's complete resistance or you hear bubbles in the wrong tank, there's likely something wrong with the selector, and while you can bypass it, they're available at parts stores for not very expensive at all. I know blowing into a gas line is a primitive form of diagnostic, but it shouldn't be just pouring fuel out, and you can wrap something clean around the end of the line.

 

[chuksk20]

Thank you, off to work I go, but I will try that in the morning. I appreciate all the feedback, so glad I stumbled upon this site.

 

[smoothandlow84]

Probably the old gunk in the bad fuel tank clogged your in tank sock filter...or the filter itself fell apart and is lodged in the pump . I did the same thing with my truck. Decided to try out the passenger side tank, it ended up sucking not only bad fuel but also the filter into the pump. I ended up dropping both tanks, replacing both filters and both pumps. I also cleaned out the tanks. Its no suprise how much garbage builds up in the bottom of the tank in 30 years.

 

[chuksk20]

I did a temporary bypass of the tank selector valve and the truck fired right up, now I know the part I have to get. Thank you everyone for the guidance, it is very much appreciated.