Question: How to Clean Fuel Tank

ken_23434

Petty Officer 1st Class
Joined
Jul 28, 2008
Messages
313
I will put my question first, so you don't have to read through all the details of why I am asking it...

How well do you think it would work to clean out an old fuel tank (18 gallon plastic, under the floor of a 18' runabout) by placing an "universal" electric fuel pump (say from Autozone or Pepboys) hooked up to the boats fuel tank, then going through the inline water separating fuel filter and then directed back to the fuel inet on the back of the boat? ie by passing the motor completely, just using a temporary pump to circulate the tank through a filter and then back to the tank.

Of course, this would be done outdoors. I would make up a temp wiring harness to give the pump power and provide a switch to turn it on and off. Then, I would just let it run and monitor the discharge rate into the tank. When the flow seemed to get low (or maybe hook up my fuel pressure gauge into the discharge line) I would shut if off, replace the fuel filter and then run it again.

Do you think this would work to clean out the years of junk in the tank that are clogging up my filters while the boat is running?

I would rather clog up filters in the drive way but without running the motor. I even thought about towing the boat, while the pump is recircing my tank. And drive down a gravel road to bounce the boat a little and make sure the junk in the tank is all agitated.

My redneck in me might be showing. :eek:

Below is the history behind the question, in case you are interested.

Here is the latest issue I am trying to tackle with my project boat.

The fuel tank is under the floor and I do not want to cut up the floor to pull the tank out. (Hopefully, I won't have to.) Some of the posts I have read on here talk about a 6 or 8" opening and reaching into the tank with your arm and a rag to clean it all out. Well, that is not an option with the design of my tank. My fuel sending unit has about a 1.5" opening, so I cannot reach my hand into the opening. The place where the fuel line and vent go are molded in nipples into the plastic tank. Some of the posts I have read on here talk about a 6 or 8" opening and reaching into the tank with your arm and a rag to clean it all out. Well, that is not an option with the design of my tank.

I drained out all the old gas. I have no idea how long the boat had sat before I got it or how much gas was in the tank when it was last parked. I filled the tank completely, hoping that would dilute the crap in there more and lessen the impact on how the engine ran.

I had a slight ping at part throttle that seemed to get worse as I opened it up more. When I came off the gas, it went right away.

I checked the timing and changed out the fuel filters. The next time I took it out, the ping was all gone. My son and I were out for a little over an hour and had it wide open for a while too. The ping started to return. As before, the pinging only started when the throttle was opened a fair amount. When it started to ping, I could come off the gas a little and it would go away. It got progressively worse as we returned to the dock.

Changed out the filters again (I bought a bunch) and took out the boat again today. This time, I had 2 more people in the boat, so the engine was working harder that previously. The pinging seemed to start much sooner than before. Now, the tank is about half full now (I have only filled it once, that tank is now half used.)

I am pretty sure the ping is just a lean condition from the filters getting clogged. I was hoping they would not clog this quick, though.

Trying to figure out a way to clean or polish the fuel in the tank brought me to the above question.
 

ken_23434

Petty Officer 1st Class
Joined
Jul 28, 2008
Messages
313
Re: Cleaning Fuel Tank

Re: Cleaning Fuel Tank

Well, I was hoping to get some insight on if this had been tried before and if it was a good idea or not...

I picked up the pump on the way home from work today, and it has been recircing my tank now for about an hour. The fuel flow rate seems to be constant, although I do not have anything to measure its flow rate. I think the pump was rated at 42 gph. That should cycle the fuel in my tank about 2 per hour. I started with the bow raised all the way, to try and force all the gunk in the tank to settle to the back and hopefully get sucked up. I also have lowered the bow all the way, then just lifted the front rapidly and then lowered it. I was hoping that would slosh the fuel around to get everything suspended and then sucked through the filter.

I will try this off and on through out the week, then take the boat out this weekend to see if it fixes my problem.
 

ken_23434

Petty Officer 1st Class
Joined
Jul 28, 2008
Messages
313
Re: Question: How to Clean Fuel Tank

For some reason, it seems like I am talking to myself... :D

In case some one else stumbles across this tread from a search, I will report on my results.

I ran my "experiment" for about 8 hours total over 3 night. Swapped out 3 of the Sierra water separating fuel filters while doing so. I never saw a big reduction in the flow rate, so I probably could have kept the same filter in the whole time. I wasn't sure what happens to those filters though, when they reach their capacity for the water removal, so I changed the filter thinking it would get any water that might happen to be in the tank.

I took the boat out this weekend, ran it for about 2 hours and my pinging never returned. So, I would conclude that my universal fuel pump experiment to clean out the junk in the fuel tank was a success.

Now it's off to all the other "issues" with my project boat. Pretty soon, I can drop the phrase "project" when I refer to my boat.
 
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