Clearing Fuel Line(s)

[Rick B.]

I am very close to starting up my newly restored/rebuilt 72 but want to be sure everything is fine with the fuel supply before turning it over and breaking in my big block.
Because the restoration dragged on for years longer than I planned, I am concerned there could be residual fuel dried/gummed up in the lines.
I assume blowing out the lines with compressed air ( from the engine compartment back) would be okay as long as the pressure is kept to a minimum.
Can anyone offer any advice or tips as to what to do or what to avoid ?
Can both lines be pressured up?

Thanks in advance !

[John D.]

Re: Clearing Fuel Line(s)

Rick, Blowing air thru lines that are have varnish/gum in them won't solve the problem. You need to clean out the lines with whatever it takes to get them spotless.
Problem is more rampant that ever with our gas going to pot so quickly. JD

[Edward J.]

Re: Clearing Fuel Line(s)

Rick, I think the only way you can clean out the liine is with compressed air, short of replacement, I think the main concern will be debree in the lines ,most of what fuel that was in the line will have evaporated over the years.Maybe put a cheap fuel filter on for now and change out in a few hundred miles.

[Jack H.]

Re: Clearing Fuel Line(s)

I agree with John. Compressed air alone won't unload ALL of the internal varnish that might have built up, but there are pro/con issues here.

(1) Preceeding the compressed air flush with a HEALTHY squirt of carb cleaner will lift MAJOR deposits.

(2) Repeated application(s) of carb cleaner and compressed air with some time for the carb cleaner to soak in and 'lift' contaminate build up helps increase the effectiveness of the fuel line clean out.

(3) For the most part, the fuel line remains submerged in liquid gasoline since, unlike a carb with vent stacks on the fuel bowls, its not open to the air to foster varnish build up due to fuel evaporation.

(4) Given #3, the best time to flush fuel lines is at the BEGINNING of the restoration process when you've just disconnected the engine + tank ends of the pipeline vs. YEARS later when you're getting ready to reconnect the system...

[Jim T.]

Re: Clearing Fuel Line(s)

To ensure you will be starting with a clean tank you could buy an new tank filler neck gasket and remove the rubber surrounding the filler neck and then remove the filler neck. This will give you access to hand clean the inside of the tank with a wipe down not using any water product. Generally you can view inside the tank with only removing the gas cap and using a strong flashlight to see any debris.
You could also replace the rubber gas line going from the tank to the frame rail gas line. With the old hose removed inspect the end of the line and use a can or two of GUMONT spray carbruetor and spray it into the gas line and have a clean container at the end of the line to catch the cleaner and see what it brings with it. Just an idea, have not had to do it.
Have cleaned inside my 70's tank ro remove a small amount of water about 30 years ago.

[Rick B.]

Re: Clearing Fuel Line(s)

Thanks for the feedback.
I appreciate now what I "should've done" but unfortunately I did take steps in the first years to prevent varnishing from occurring- it's the unavoidable delays and long term of the project that is coming back to bite me now.
When I started the restoration the lines were clear and free-flowing. At the beginning I had initially closed off the fuel pump end of the lines with a pinched off hose and made sure the tank was kept full with fresh gas. However, while in the beginning some fuel would seep out on its own whenever I opened up the engine compartment end of the line, now nothing trickles out. I have to assume therefore that something may be impeding the flow of gas. Having said that I am not totally sure that the design of the system would allow for normal flow of gas on its own without the drawing action of the fuel pump. I thought some fuel would siphon out on its own but as I said nothing seems to come out at present.
I will spray carb cleaner in and blow through towards the gas tank in an effort to loosen whatever "may" be lurking within.
Can both lines be safely pressurized or just the return?
What should I be looking for in the way of tell-tale signs things are good or bad?

Thanks in advance !

Rick

[Rick B.]

Re: Clearing Fuel Line(s)

Jim, the tank is clean and free of debris. I would always use a LED flashlight and have a good look around in there each time I was replacing the batch of fuel in the tank.
Frankly I am now concerned that if I blow out whatever may ( or may not be) in the line (from the engine compartment back towards the tank) that the gummed up varnish will just end up getting trapped inside that filter sock only to be suck up back again and drawn down through the line.
Again, I want to be clear here....I don't know if I even truly have an obstruction problem, I'm just careful and don't want to deal with a fuel starvation problem while I'm trying to break that engine in.
You guys have been helpful with your thoughts/feedback and I truly appreciate it !
I wanted to avoid more work this close to being done but perhaps I better drop the spare tire tub and see what I can do from that end.


Rick

[Edward J.]

Re: Clearing Fuel Line(s)

Rick, if you go the carb. clenaer route make sure that you cover the other end of line, don't want any of this on the paint of car on the engine -it will in short order eat right in to the finish.

[Jim T.]

Re: Clearing Fuel Line(s)

Jim, the tank is clean and free of debris. I would always use a LED flashlight and have a good look around in there each time I was replacing the batch of fuel in the tank.
Frankly I am now concerned that if I blow out whatever may ( or may not be) in the line (from the engine compartment back towards the tank) that the gummed up varnish will just end up getting trapped inside that filter sock only to be suck up back again and drawn down through the line.
Again, I want to be clear here....I don't know if I even truly have an obstruction problem, I'm just careful and don't want to deal with a fuel starvation problem while I'm trying to break that engine in.
You guys have been helpful with your thoughts/feedback and I truly appreciate it !
I wanted to avoid more work this close to being done but perhaps I better drop the spare tire tub and see what I can do from that end.


Rick

If you do it, only put the cleaner in from the rear to exit the front. If your gas line from the tank to the steel fuel line on the frame, it might be to your advantage to use newer fuel line that is manufactured for the gas we have to buy at the pump now. If put enough gas in the tank, it will gravity flow for inspection into a clean container from the line disconnected from the fuel pump.

[Steven B.]

Re: Clearing Fuel Line(s)

I agree with blowing from the back to the front because you do not want anything entering the tank (or if the line is disconnected before the tank there is a good chance of splattering in the rear) and you can capture residue before the fuel pump. You can disconnect line from the tank and blow forward from that point. I have done it before and ready to do it again---

[Jean C.]

Re: Clearing Fuel Line(s)

Rick, you have probably already thought about this, but if you first attach a length of rubber hose to the fuel line at the pump end, you will be able to better control where the carb cleaner and debris goes when you inject air from the tank end.
Best regards,

[Chuck S.]

Re: Clearing Fuel Line(s)

I am very close to starting up my newly restored/rebuilt 72 but want to be sure everything is fine with the fuel supply before turning it over and breaking in my big block.
Because the restoration dragged on for years longer than I planned, I am concerned there could be residual fuel dried/gummed up in the lines.
I assume blowing out the lines with compressed air ( from the engine compartment back) would be okay as long as the pressure is kept to a minimum.
Can anyone offer any advice or tips as to what to do or what to avoid ?
Can both lines be pressured up?

Thanks in advance !

Actually, my opinion is that blowing the fuel lines with compressed air and carburetor cleaner will do little to remove gum and/or other dirt stuck to the inside diameter of the fuel lines.

To get the lines scrubbed completely clean, here's another off-the-wall idea for your consideration : Use compressed air to blow a strong nylon cord through the fuel line. Then attach a properly sized "patch" near one end of the cord, trying it repeatedly to insure that it does not fit too tightly in the bore of the tubing...remember that your fuel line is going to have some sharp bends.

Apply some solvent of choice to the patch and pull it slowly through the line, much like cleaning a gun barrel (gasoline is probably a good choice for the solvent...not Hoppe's No. 9. ).

My opinion is there is little risk to the cord breaking and the "patch" becoming stuck in the tubing...application of compressed air to one end of the fuel line should fire the patch out the other end like a bullet.

[Rick B.]

Re: Clearing Fuel Line(s)

Absolutely ! Thanks again to all for your suggestions !

[Mark H.]

[Perry M.]

Re: Clearing Fuel Line(s)

This is the method I use. I spray cleaning solvent into the line and then take one of those sponge rubber ear plugs and squeeze it into a shape that fits tight inside the tube. Then use compressed air to blow the ear plug through the line. Have a catch can at the other end so you can retrieve the plug and solvent. A rubber hose over the steel line will aid in the recovery. You will probably have to do this several times with a fresh plug each time.