Fuel system question

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I got my old tank out and it was crusty beyond belief. Blew out the lines and removed the carburetor. My question is should I use compressed air to blow back the fuel from the mechanical fuel pump? Don't want to hurt anything.
 

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73 Grande will undergo three phase build process. Phase 1 is to make roadworthy. Phase 2 is interior/exterior restoration. Phase 3 is ++ performance.
I think we need more info. Maybe you’ve provided info in other posts, but taking your question at face valve, if your asking if blowing the main fuel line from the fuel pump back to the outlet on the tank will help, sure. Of course, make sure to have the line free from the tank and have a bucket 😁. But as far as my experience goes, and this is where you might have already told us, many times, if the car sat for a long time, that stock steel line is internally rusted and cleaning it will not solve the problem.

I had this exact problem on my 73 Grande and ended up replacing the line after three rounds of attempting to clean it with various cleaners. Since you’ve pulled the sending unit, I would at least replace the fuel sock and I’m assuming you’re going to clean the tank or if that is too far gone, replace the tank. Fuel issues can be a bit of chasing your tail if you don’t follow the fuel path in cleaning/replacing that path. You’ve got to ensure the tank is clean, then a new sock to make sure nothing gets into the fuel line, then the line is clean, then the fuel pump does not have any junk in it, then the carb. This is likely not new to you, but I haven’t always taken my own advice to my detriment.

My 2 cents.
 
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I think they have a check valve in them, but not positive. I would be hesitant to use the fuel lines and pump if they have rust in them. I would think about replacing the entire fuel system if everything is rusty and crusty. The rust won’t go away, it will only get worse.
 

Doug's 73 Mach1

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There is typically a mix of 3 rubber fuel lines and steel tubing between the fuel pump and gas tank sender. The rubber lines may not hold up to much compressed air pressure if they old originals. Same is true of the fuel vapor vent line running from the top of the tank over to the blue vapor canister behind the right shock tower. It would be a good idea to change the rubber line pieces out if they are still original. While rubber lines are all removed, blow out the steel fuel lines with compressed air. There is typically a sort of hidden rubber fuel line below the master cylinder down low on the fuel line from the tank to the fuel pump.
 
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Here's my 2 cents worth from my own experience with crusty fuel lines.
"If in doubt, replace it all".
A new tank is not that expensive. Buy the Spectra Premium F32A, Dorman 692232 sending unit, (I used) Delphi MF0007 fuel pump, all from Rock Auto. The 3/8 SS line I bought from NPD. Rubber tubing needs to be Fuel Injector grade hose as it is ethanol resistant (inside). PLEASE make sure to use the correct fuel line clamps,
NEVER worm gear clamps.
Here's a pic of my old rusty line which actually broke in two when it was removed.
There has been many post on this subject if you care to search.
 

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Hemikiller

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I'd replace the line going forward, but for temporary use, you should be fine. Blow compressed air into the line below the washer reservoir and like others have said, be sure to replace all the rubber sections. The V8 cars had a rubber "jumper" line below the master cylinder, that connected the main fuel line to a steel transfer line that came out below the washer tank. I would also install a clear disposable filter before the pump to catch any junk that makes it's way forward.

 
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