Fuel pump issues

Longest running airboat discussion on the internet.
Post Reply
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Fuel pump issues

Post by bbrickham »

Currently having non stop issues with new boat and fuel pumps going bad. Fuel pump started with being mounted above tank with water separator and would keep running dry like it couldn’t keep up. After that we moved pump below tank on the floor to get it low as possible. Again after about an hour of running we ran out of pressure and pump started screaming. With coast guard regs our tank doesn’t have a port at the bottom of the tank. It’s an 80gal tank fed from the top. What’s everyone’s 2 cents on how to fix this problem? Add a port to the bottom of the tank and call it a day? Fuel line is -10 through pre filter to pump and then -6 to water separator and to the motor.
Polbear
Southern Airboat Member
Posts: 10
Joined: Tue Jan 29, 2019 11:14 am

Re: Fuel pump issues

Post by Polbear »

Check your tank vent and make sure there's no obstructions/occlusions in the line before the pump
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

Tank vent is good and filter was checked even have ran it with cap open in hopes that was the issue. It will prime itself fine and then after being on pad for a while it’s like the pump can’t keep up and it’s like it is sucking air and won’t stay primed
Gary S
Site Supporter - I
Site Supporter - I
Posts: 1771
Joined: Wed Mar 03, 2010 3:30 pm
Location: Redlands

Re: Fuel pump issues

Post by Gary S »

Sounds like a pickup problem, like it is too close to the bottom or sucking air. I would try sticking a hose in the fill and duct taping it shut and taking a short ride,hopefully without a full tank.
L&LLandServices
Southern Airboat Member
Posts: 17
Joined: Thu Nov 05, 2020 1:52 pm
Location: Seminole County FL

Re: Fuel pump issues

Post by L&LLandServices »

Have you pulled your pickup tube out of the tank and checked for cracks or leaks ?
2021 14x8 Alumitech, 548CI Mike Ford Big Block
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

Haven’t checked the pick up tube but I believe it’s a welded in pick up tube with a brass 90 at the top I’ll have to take it apart and see if it isn’t a tube connected to the 90 the tank is 2ft tall as well it’s a big 80 gal tank maybe the hight is a reason that it can’t pull from the bottom but with a full tank I wouldn’t think it should have a problem sucking
One Eyed Gator
Southern Airboat Member
Posts: 1375
Joined: Wed May 30, 2007 11:33 am
Location: Ocala,Fl

Re: Fuel pump issues

Post by One Eyed Gator »

I have always run 2 pumps supply and lift.

What fuel pump you running.

Is fuel line in good shape, not collapsing
Is prefilter letting air in or maybe another connector
LIke said above leak or crack in pickup tube
What micron water/fuel seperator you running?

Just some things to check
Good luck with the issue
hdsadey
Southern Airboat Member
Posts: 333
Joined: Sun Jul 01, 2012 7:42 pm
Location: venice fl.

Re: Fuel pump issues

Post by hdsadey »

I had a similar problem. The new 408 would run fine for awhile and then it would start to stumble. Sometimes even shutting off. FiTech Injection with the pump at the bottom of the tank. I thought the pump was going south. New pump and as I was swapping them out I decided to open the pre-filter. Low and behold it was full of aluminum shavings from installing the sump. Vacuumed the snot out of it after I welded it on but that sticky aluminum clung to the walls of the tank. Funny thing it didn't show up for almost 2 years of running!!! Won't forget that one!!!!
02 Predator 12' 0320 Lycoming
2019 Circle H 408 Windsor DD Sig Series 74"
99 Donzi 16 Classic 350 Vortec
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

Motor is from water thunder and everything is per his instructions 10 micron and a walbro pump he has been super helpful but it seems like he’s stumped as well. Boat builder has put the same style set ups in the last few boats he’s build with no issues. Like I said the boat has probably 10 hours on it so it just seems so strange that there would be any obstructions. Pre filter was spotless
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

One picture is how it was mounted before and then how we changed it to try a get it lower
Attachments
C09FFE44-737B-48E3-9CA7-96B3586E6D26.png
60A89877-8410-4F19-B5EF-063DBD264830.png
Swamp Thang
Southern Airboat Member
Posts: 62
Joined: Mon Jul 25, 2016 9:32 pm
Location: Hudson and Inverness Fl.

Re: Fuel pump issues

Post by Swamp Thang »

I had a very similar issue on a GPU boat, it ended up being a bad/corroded anti siphon ball & spring assembly at the top of the pick up tube... removed the ball & spring and no more fuel issues, never had any problem priming the fuel system without the anti siphon valve. I can't tell from the pics if yours is the same type but it is definitely worth checking
One Eyed Gator
Southern Airboat Member
Posts: 1375
Joined: Wed May 30, 2007 11:33 am
Location: Ocala,Fl

Re: Fuel pump issues

Post by One Eyed Gator »

Maybe try a straight fitting instead of the 90 on the inlet side of the pump

Just a thought
User avatar
OneBFC
Southern Airboat Member
Posts: 672
Joined: Tue Sep 11, 2012 1:04 am

Re: Fuel pump issues

Post by OneBFC »

Actually, that 90 near pump inlet could very well be your demon. Pumps typically need 5x pipe diameter of straight tubing prior to the pump inlet as an absolute minimum to avoid promoting cavitation of the pump impeller.

Ideal is considered 10x pipe diameter.

Worth a shot, easy enough to do.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
Life begins at 2 BAR, Just a good ole boy
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

OneBFC wrote:
Wed Jun 09, 2021 5:36 pm
Actually, that 90 near pump inlet could very well be your demon. Pumps typically need 5x pipe diameter of straight tubing prior to the pump inlet as an absolute minimum to avoid promoting cavitation of the pump impeller.

Ideal is considered 10x pipe diameter.

Worth a shot, easy enough to do.
Holy shit I didn’t even think about that! I’m a plumber too so that makes complete sense! As soon as it hits that 90 it probably gets air after time. Thanks!!
bbrickham
Southern Airboat Member
Posts: 8
Joined: Fri Jun 26, 2020 9:54 pm

Re: Fuel pump issues

Post by bbrickham »

Well turns out I have a plastic dip tube and at the bottom of it there was a little mesh screen that was cluttered full of shit. Ripped that out and she was good as gold. Really wish I had checked that before we spend money on 3 fuel pumps.
JLP3314
Southern Airboat Member
Posts: 38
Joined: Tue Nov 17, 2009 12:31 pm
Location: Hawthorne, Florida

Re: Fuel pump issues

Post by JLP3314 »

Easy fix is always good!
I had pickup tube in a Ford truck that the pickup tube was 1/8" of an inch from the bottom of the tank, (from the factory) giving issues for years.

Lord...how everybody's loving the gas prices nowadays right!
Don't waste your time-its the only thing you can't get back, (Cntry141IQ/John had another thousand of these before he went sliding into the sky). :-(
Post Reply

Return to “Airboat Talk”