Trying to get fuel to the carburetor -- nothing from fuel pump when engine is cranked so disconnected both lines to/from tank. Larger line, I'm supposing supply, is open as evidenced by bubbles in tank when low pressure air is applied. No gas flows naturally (haven't tried mouth to hose suction, yet). But, the smaller line, I'm supposing return, seems to be plugged because low pressure air does not create bubbles in tank AND pressure in line is evident when blow gun is removed. I can't figure why there might be a check valve or something in return, so why is return line not allowing air to flow? Would I ruin anything by replacing the fuel pump, knowing that I may have to do something with the return line later? (Car is in garage and lift is 200 feet up the hill in workshop; would be a lot easier to crank car with new pump and move up to workshop with lift to investigate return line further)

Thanks for thoughts!!

 

Shouldn't hurt anything, especially for a short jaunt up the hill.
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Thanks.,

 

If you have a small gas tank around like from a mower, other small machine, or boat you could rig it to sit above the carb and gravity feed fuel into the carb. You could bungee cord the small tank to a spot higher then the engine and run a rubber hose to the fuel inlet on the carb. Double check your connections to this temporary tank, and use small clamps. You are working with fuel being close to the engine, so safety is key. I have used this method many times to move old cars with bad tanks and pumps short distances like you need to. You could also modify a small red plastic gas can to do the job as well. You may need to buy a cheap barbed fuel fitting to screw into the filter housing on the carb.

 

Good thought -- don't know why I didn't think of it. I actually have an engine stand equipped with a small gas tank that I could use. I suppose I could even use it with the fuel pump just to see if the pump is actually a problem or not.

Thanks.

 

True, though the pump being gravity fed by the small tank may give you a false positive. If the pump doesn't have to do any lifting it may appear good because it didn't have to do any work. You could do this test with the small tank below the level of the pump and hooked to the inlet line on the pump. And see if it gets fuel that way. If not these pumps are available and pretty cheap.

 

Absolutely. Turns out, I just happen to have a new pump -- there's another 400 ci engine sitting on the test stand without a fuel pump installed, yet. That's pretty much what got me started on this problem-solving project in the first place. Since I had the new pump and had questions about the older pump, I figured I'd take a few steps to check things out before using the new pump. That's when I found that the return line was apparently plugged or something. My "To-Do" list is slowing the problem-solving down a bit!

 

Well as they say slow progress is better then no progress! Sounds like you've got everything you need for a few tests, and a quick trip up that hill. Next would be a ride on the lift to see what's up with that return line. I would start with the rubber hoses on both the intake and return lines as they could be collapsed internally.