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Fuel pump issues

B

bbrickham

Member
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.
 
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
 
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.
 
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
 
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
 
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!!!!
 
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
 
One picture is how it was mounted before and then how we changed it to try a get it lower
 

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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
 
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.
 
OneBFC said:
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.
Click to expand...

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!!
 
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.
 
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!
 
I have been baffled on where to mount the fuel pump,manufacturers recommend pump as low as possible because the pumps 'push' better than pull most boat builders have their pumps mounted way above the tank (upper engine front bracing), seems that a pump will fail early if it has to pull...who is right..b.t.w. I use carter pumps,love them
 
It is also a “best practice” to have an inline filter before the pump to trap any larger particles that could bind or damage the vanes.

We run an inline disposable stainless canister before the pump and a water separator filter after the pump. It works extremely well.
 
Coast Guard regulations require any pump, fuel lines, filters etc. mounted outside the tank to be located higher than the top of the tank. Any line that runs below the top of the tank is subject to siphoning from the tank (if cut) and filling the bilge with fuel. If anything runs below the top of the tank, the system needs an anti-siphon valve, which basically makes the suction pressure the same or worse vs. above the tank so only do it if CG regs don't apply (and you are good with a bilge full of fuel in the am).

The best place for an EFI fuel pump is inside and at the bottom of the fuel tank, sock on the inlet, Racor on the outlet. If that doesn't work, install a lift pump with suction screen at the top of the tank, feeding a Racor, feeding a HP EFI pump above.
 
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