Priming the fuel lines

[davepl]

Note well: I have no idea if this is smart or safe. I'm just reporting what I did because it was interesting. Do not attempt. Consult a qualified mechanic.

I have a new engine that's been sitting a year or so since the dyno. While I am priming the oiling system, I still don't want it to have to crank for 30 seconds to 'suck' fuel from the tank into new dry lines.

What I did was detach the line at the carb, stuck it in a gallon gas can and had someone monitor it. I then used a rag and tire inflator air hose to lightly pressurize the fuel tank. Since mine is unvented (and this would not work otherwise) the only way out is for fuel to go out the pickup. There was still some pressure when I released the rag which coughed up a light mist of fuel that I wasn't quite expecting.

Sure enough with just a few psi of pressure it took maybe 5-8 seconds for fuel to appear in the jug. Now my lines are primed, I can check for some leaks before starting, and it won't have to crank a long time.

I know I could pour gas in the carb and fire it up and hope it runs long enough to prime the fuel pump (which is what I've always seen done). I've twice now seen people set their cup/bottle/whatever of fuel on fire when it backfired. One guy panicked and threw the Big Gulp cup of burning fuel. Can't believe they saved the garage.

This was my attempt to avoid that whole scenario. There may be better ways.

[69chevytrucker]

Milton makes a tool the is like a blow gun with a hose on it stick the hose in the fuel line and do a few short blasts and it will pull the fuel but it will shoot out the blow gun if your not careful but there is like 4 ft of tube so if you watch you will see it come up the line then stop the whole pour the gas in the carb is not good my dad did it when he was young and it back fired and he caught fire and burnt most his upper body bad

[turp mcspray]

I've done the very same thing, many times!

[RichardJ]

Have done the same many times. It fills the carbs, lets you check the accelerator pumps and as you said, it just as importantly checks for leaks from the tank all the way to the carb.

[BluTrukker]

I work on military equipment for a living, and some of the older vehicles were notoriously hard to prime if you ran out of fuel(which happened a lot!) We drilled and tapped a hole in a fuel cap and threaded in an air chuck with a regulator on it. 3-5 PSI can prime a fuel system quick! I have used the rag and blow gun trick many times. It is also useful when draining a cooling system to remove that last bit of coolant that is always in the hoses,so you don't have a mess when you take of hoses.

[slikside]

Originally Posted by davepl

Note well: I have no idea if this is smart or safe. I'm just reporting what I did because it was interesting. Do not attempt. Consult a qualified mechanic.

I have a new engine that's been sitting a year or so since the dyno. While I am priming the oiling system, I still don't want it to have to crank for 30 seconds to 'suck' fuel from the tank into new dry lines.

What I did was detach the line at the carb, stuck it in a gallon gas can and had someone monitor it. I then used a rag and tire inflator air hose to lightly pressurize the fuel tank. Since mine is unvented (and this would not work otherwise) the only way out is for fuel to go out the pickup. There was still some pressure when I released the rag which coughed up a light mist of fuel that I wasn't quite expecting.

Sure enough with just a few psi of pressure it took maybe 5-8 seconds for fuel to appear in the jug. Now my lines are primed, I can check for some leaks before starting, and it won't have to crank a long time.

I know I could pour gas in the carb and fire it up and hope it runs long enough to prime the fuel pump (which is what I've always seen done). I've twice now seen people set their cup/bottle/whatever of fuel on fire when it backfired. One guy panicked and threw the Big Gulp cup of burning fuel. Can't believe they saved the garage.
This was my attempt to avoid that whole scenario. There may be better ways.

Originally Posted by 69chevytrucker

Milton makes a tool the is like a blow gun with a hose on it stick the hose in the fuel line and do a few short blasts and it will pull the fuel but it will shoot out the blow gun if your not careful but there is like 4 ft of tube so if you watch you will see it come up the line then stop the whole pour the gas in the carb is not good my dad did it when he was young and it back fired and he caught fire and burnt most his upper body bad

From High School Auto Shop safety over 30 yrs. ago:

When priming a carb, do it BEFORE attempting to start the engine, and place your priming container on the ground outside of the engine compartment. Never attempt to keep an engine running by pouring fuel directly into the carb....otherwise, the above can happen.

[davepl]

My Dad also knew a guy who was badly burned doing this; but my mom was a burn ward nurse for decades and she saw a -lot- of that. That, plus my first "oil gauge line on header" fire, has made me pretty cautious about gasoline. That and never let the grandparents deep fry with an electric deep fryer on the kitchen island while running the cord to the wall outlet. You can do the math on that one :-(

I do want to reiterate what someone said above: it takes very little pressure (like 3-5 psi) and then patience, though it sounds like sometimes it happens very quickly.

You do not want 100psi of pressure in your tank (which would explode or expand your cab) or your lines, plus you'll be venting fuel and/or air for a long time to get rid of it!