Yesterday I decided to try to do a couple of things on the '77 Bobcat (2.3L auto) sitting in the garage. When I bought the car, the folks started it by pouring gas directly into the carb. They said this was because they thought the fuel pump was out; it worked and she ran. The last couple of days I had purchased goodies to start bringing her back (fuel pump, air/oil filters, plugs/wires, distributor cap/rotor; new battery; radiator hoses and belts) and yesterday was the first go round. I put in the battery and applied a dose of starting fluid into the carb and she fired right up. She is a loud one (not much of an exhaust system) but she ran. Once the starting fluid burned up she would shut down. I decided to try putting gas in the tank to see if the fuel pump actually worked. I only put in about a gallon and initially I had to use starting fluid again, but she kept running beyond when the starting fluid would have burned off. I saw gas bubbling up through the top of the carb (at least I'm assuming it was gas) in a surprising quantity. It was almost like dirty water. My concerns are this: In this type of engine, is it normal to see this much fuel bubbling to the top of the carb? Considering the color of what was coming out of the carb, how much risk am I taking by letting the engine run to burn through whatever it is? I don't desperately want to drop the fuel tank as I've never done that and I'm afraid I couldn't get the straps to function well enough to hold it on again. I have not changed the oil in the engine, but will be this weekend, half expecting that when I do it will get pretty grungy and I may opt or need to do it again after letting the car run for a while to get some of the crud out of the engine. Also, in light of this, I'm getting a new fire extinguisher for the garage...Any help would be appreciated.
Couple of different ways you can approach this. Sounds like quite old fuel in the tank is what you are seeing. You could pull the fuel lines off at the fuel pump and then route them into a can. If you have an air compressor, take a rag to plug the filler hole and put a small amount of air pressure into the tank. It will force almost all the fuel out the lines. Second option is to rig up a small fuel can of sorts and hang it from the hood. Go directly to the carb fuel inlet connection with the fresh fuel and start the car. Using this method the fuel pump will pump the old gas out of the tank. I usually go with number one as there is less danger of lighting things up if there is a back fire. Change the fuel filter after doing the above. Depending on how long it has sit you may have to clean the carb if the float is sticking. Good luck.
A thought for the carb, based on my experiences with other types of carbs (Holley 4bbl, Carters) is that it sounds as if either A) needle and seat has dirt in it causing introduction of excessive fuel in carb. B) Float level not properly set. A trick that has been useful on the performance carbs with issue A), particularly the susceptible Holley, has been to pinch the fuel line and run the engine until it stalls.This technique has helped with the problem of a contaminated needle and seat assembly. If it doesn't work some disassembly may be required.
Thanks folks, I appreciate the ideas. I don't know what I'm going to do just yet. I need to change the oil also, and need to warm it up a bit to get it out. I'll run it for a while and see what happens. If it's just old fuel, and I can't imagine it would be anything else, it shouldn't cause any damage, should it?
The presence of old gas, in and of its self, will not cause "gas to bubble up in a large amount" in the carb. This is the reason I say there is an issue causing excessive fuel dumping. The A) and B) issues I spoke of in my previous email could potentially be caused by old fuel varnish- particularly the needle and seat issue. Of course getting rid of the old fuel is very important, but once you have be aware that your problem might (likely) still exist. If it does check the A and B issues I mentioned. Good Luck!