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How do I flush water contaminated fuel lines

T

Terry in Ottawa

Contributing Member
I've been told the fuel tank on my Johnson 25hp, J25TEEDA, has been contaminated with water.

Is there a procedure for getting the bad fuel out of the fuel lines, the fuel pump and the carburetor?
 
Terry,
After you empty your tank and clean it, hook up a temp tank with known good fuel to your engine, then disconnect the fuel line from fuel pump to carbs then crank it over (with the kill switch pulled) and let that run into an appropriate container until you feel like the lines are clear (shouldn't take long). Then reinstall lines. If you think there is an appreciable amount in the engine, pull your spark plugs and crank it over a few times to clear that old fuel through the cylinders.
 
Put the old fuel in your lawn mower and fill the tank with good fuel mix. Pull the plug on the float bowl and put a dish under it and pump the primer until good fuel comes out then go fishin!
 
Of course don't forget to figure out and correct the cause of the water in your old tank. I have almost a mountain of old plastic fuel tanks outside my shop. UV gets 'em and they "suck" in water When it rains on them. Depending on design, it could be the gauge area, the outlet line area, or on some occasions even the fill cap. Flip it upside down and check it once it has fuel in it.
 
Of course, follow the aforementioned procedures only if the water has been in a short time.......like 1 to 2 weeks. Otherwise you may be faced with more complex cleaning.
 
If you start messing with the fuel lines your likely to get crap in the carb. If yoy feel it necessary replace the fuel lines and rebuild the fuel pump. Then your all set to rebuild the carb if necessary.
 
Just got a mint 82 Johnson 7.5 yesterday. I see someone just changed the fuel line from the fuel pump to the carb. The carb had not been removed.....I can tell from the evidence. You know I will be removing the carb to clean and overhaul, if needed. Almost every fuel system problem will end up with deposits of some kind in the carb. I have a box of good quality 1/4" see through filters that are compact enough to hide somewhere under the cowling. Too much crap is introduced with the coupling and uncoupling of the supply line at the tank or the motor. I like to play safe.
 
Success.

Took a lot of cranking yesterday but the motor finally started. But by that time the battery was pretty weak and I didn't want to try any restarts. So, I recharged the battery overnight and retried today.

Started right away, idled well and accelerated to full throttle. Was able to come down to trolling speed no problem. Tried several restarts and all were successful.

I'm happy.

It's pretty easy to check for water in the fuel so it'll be part of a maintenance routine from now on.

Thanks for your help.
 
Terry in Ottawa said:
Success.

Took a lot of cranking yesterday but the motor finally started. But by that time the battery was pretty weak and I didn't want to try any restarts. So, I recharged the battery overnight and retried today.

Started right away, idled well and accelerated to full throttle. Was able to come down to trolling speed no problem. Tried several restarts and all were successful.

I'm happy.

It's pretty easy to check for water in the fuel so it'll be part of a maintenance routine from now on.

Thanks for your help.
Click to expand...

I think I would check the fuel filter and drain the carb bowl just to make sure there are no residual pockets of water that could cause problems later.
 
Just run it out of fuel when you get home in a barrel of water and store it in the running position. If you keep the fuel tank topped off it keeps moisture out.
 
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