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Clearing blocked fuel hard line

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i thought you said you had fixed this? if you can hear air coming back into the tank at a good rate then it's not plugged. just undo the fuel hose at the filter and blow with your mouth. if you can hear air passage with such low blowing pressure then it cant be that clogged. compressed air would really let you know how much air is passing by the sound.


1. unhook the fuel hose at the carb.

2. pour gas down the carb and start it.

3. if fuel squirts out of the hose you know the line,pump,filter are fine.


pay close attention to the fuel filter it will give signs. if the fuel in the filter is really low or fluctuates you have a air leak from the hose clamps. not all air leaks into the line will drip fuel out. change the old style wire clamps to new style.


also if you have a hitachi carb with the front window plate that has the little circle for a window change it out and find the full 2''x3'' glass plate from the older carbs to put in. then you can watch the fuel level in the float bowl much better. i find that alot of the hitachi inlet valves at the hose get stuck open or closed. if you dont have the big glass plate to look into tap on top of the inlet with a hammer as it starts to die. that will seat it temporarely for a moment. atleast you'll know your onto something good luck bro.

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this may have already been said but for process of elimination get 4 feet of hose and run it between the tank side of the filter or tank side of the pump and a fuel can. if it runs fine your line is clogged. if it does the same thing it is probably one of the other issues i mentioned.

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Is this a car that sat without running for years? Maybe old gas dried out in the tank? I had a plugged hard line on my "sat for 5 years in a field 510". I sprayed carb cleaner in both ends of the line and let it soak for awhile, then hit it with compressed air. I just kept doing this over and over (maybe a dozen times) until no more brown gunk came out. You may use most of a can of carb cleaner, but that stuff is pretty cheap. If you do have brown gunk in your line, I'm not sure you will be able to get any sort of wire or rod through it. Dried up gas is similar to hardened glue. You need to dissolve it. I think acetone would work too, but spray carb cleaner is way more convenient. You should stick a couple of feet of rubber line on each end of your hard line if you do this, so you don't blow brown gunk onto your car.



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  • 3 months later...

Just to update this, old gas had gelled ijn the fuel line. I took out the line and tried cleaning out both ends w/ carb cleaner.

it ended up getting left out, where it sat in the sun for about a week. the gelled gas melted and ran out out end, so after two more soakings of carb cleaner, the line is now clear and ready to go back in the car.

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  • 1 month later...

On a 1979 620, which is the fuel line? The line on the SIDE of the tank, or from the top? The side is working supplying gas to the engine. The top line is plugged. A 1977 manuel indicates the top line for vapors going to the seperator. If it ISN"T the side line and I drive with it that way, when the fuel level drops below, I will starve for fuel. Not a good thought!! Thanks.

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