Perplexing fuel distribution issue

I've had my boat a year now and am just starting to use it after several maintenance issues. When I purchased the boat I knew we had a fuel quality problem so before purchase I had the aux tank fuel professionally cleaned. To get the boat home I added 50 gal of fuel to the aux tank bringing it up to about 60 gal and left the tank selector valves in the aux position. I used about 10 gal to get home leaving about 50 or so gal left.

The boat has 3 tanks, the aforementioned aux tank and the L and R tank. I had those tanks cleaned and filled them up with new fuel and left what was remaining in the aux tank. I repositioned the tank selector valves so the engines would burn out of their respective tanks and they have remained in that position until today.

After about 20 hours use, I refilled the main tanks and noticed the L tank took about 30% more fuel. I did not add fuel to the aux tank. Again after 20 hrs of use I refilled with the same results. I did not check the aux tank capacity.

I took the boat out today to test a newly installed impeller and also to run some fuel from the aux tank to make sure the fuel quality was OK. I ran fuel from the aux tank only to the starboard engine, not wanting to press my luck. Everything ran fine. When I got back I checked the fuel gauges and to my surprise the aux tank gauge showed full and the L and R tank gauges showed just slightly above 3/4 full. I thought that perhaps the aux tank fuel sending unit had failed since I had not added fuel to the aux tank in over a year and it had about 50 gal last time I checked.

I pulled the sending unit and indeed the aux tank was full, in fact too full. I pumped about 15 gal out of the aux and into the L tank.

So, whats going on. Obviously the L engine is not burning 30% more fuel, it's somehow putting the return fuel into the aux tank.

The fuel transfer valves are of the ganged variety in which both the return and feed are on one handle. The handle has a square groove that fits a square stem on the valve. If it was positioned incorrectly it would be obvious because the markings would not line up with the handle. It is a 3 position valve, Off - Aux - L or R as appropiate. This allows the aux tank to feed either engine or the L or R tank to feed it's respective engine only.

There are 6 ports on the transfer valve. 3 for the feed and 3 for the return. The 3 ports closest to the handle are slightly larger than the other 3 behind them. One of the larger ports has a hose attached that goes to the Racor filter. I cannot tell where the other 5 hoses go.

Where do I start figuring this out??

Use different colored masking tape and find a helper.

Pull on or move each hose , marking as you go till the hoses are marked from end to end.

Then inspect as much as you can for a jumper or other connection that could screw up the sustem.

Draw a map of what you have .

Be esp careful of extra "balance " or other lines from one tank to another.

Be careful of "vent" lines that connect tanks , they might siphon.

I don't suspect a hardware issue or mis-placed fuel line. The boat is 13 yo, and the PO did very little work upgrading or modifying the boat and I don't think he ever had a fuel issue. I looked very closely at the fuel tank selection valves and it doesn't appear they have been tampered with since installation. Of course I can't verify this.

This is what I've done to the fuel system.

* Repositioned the dc electric fuel transfer pump switch on the helm and added LED lights to indicate fuel pump operation. This pump transfers fuel between the L and R tanks to rebalance in the event of prolonged genset usage or single eng operation. I have never used the pump except yesterday when I ran a hose between the aux tank in thru the removed fuel sending unit then to the pump. I then used the pump to transfer fuel out of the very full aux tank to the L tank. The pump has a dc circuit breaker on the DC elect panel that always remains off.

* Added a second fuel filter after the Racors. I cut the fuel line after the racor and inserted the new filters.

* Added a squeeze bulb priming system to both engines. This entailed cutting the fuel line prior to the racors and inserting the squeeze bulb priming system.

Attached are pictures of the stbd fuel transfer valve. The handle has been removed. The line going down is the engine feed line because it goes to the racors or now to the squeeze bulb priming system then to the racors then to the second filter that I added then to the engine.

I've noticed that each line going into or coming out of the fuel tank has a shutoff valve, all open that I can see. I had the fuel cleaned by two different companies and It is possible one of the guys working on it inadvertently s/o one of the valves, but as far as I can see this has not happened. I'm trying to think of a situation that would allow return fuel to go to a different tank than from which it was pumped from and regardless of how you position these s/o valves I can't think of a way of this happening. If a return s/o valve were closed and the engine run, a problem would quickly develop. The fuel cooler lines will not take much fuel pressure and if return fuel has no where to go the lines in the fuel cooler will expand to the point of not allowing water to flow thru the cooler and the engine will overheat. Additionally I've run the boat 60 hrs since doing the filter and priming work and no engine problems developed.

I think I'm missing something much simpler here. I'm assuming it's fuel return that's filling the aux tank and depleting the port tank. But maybe it's something else.

Summary: Boat fuel system worked properly when I bought it (as far as I know).
**************** I worked on the fuel system as stated above.
**************** I immediately have fuel distribution problems.

Tim, is the Aux tank lower than the other tanks? It syphoning a possibility here?* You may have explained this, but with three tanks, when one is selected to provide fuel is there a return from the engine that as a result of the valving goes back into the tank from which fuel is being drawn?* Is the design of the system intend for the Aux tank to be your 'day tank', which would then be the only destination for the return from the engine?*

Do you live near the 'Car Guys' on PBS?* I heard them tell of a joke they played on a friend who was bragging about the mileage he got on his car.* Each afternoon while he was in his office, they would add some gas to his tank, slowly increasing the mileage to the point where it was over 100 mpg.* Then, they started removing the gas until it got down to 8 mpg before revealing the prank.* Maybe that's what's going.......

Delfin, the car guys are great, I love them always made me laugh,

The design is to be able to use any tank at any time. Fuel returns to the tank from which it was taken. At 1 mpg this is the only practical design.

However, I will call Carver on Monday to discuss this and find out if it's operator error.

I'd be suspect that the fuel polishing folks had the lines off and didn't plumb it back correctly.

Just looking at your pictures and what I see is the valve to the left is set to Aux. I assume this is the return line from the engine and is going where directed. In this case the Aux tank.

If you are setup like I am with three tanks with a PAIR of 3way valves (4 hoses connected) one is for the SUPPLY and the other (smaller sized hose on mine) is the RETURN. The safe (only way I run mine) is to have both valves set to the same tank at all times.

Just last year I had a situation similar to yours while polishing the fuel prior to spring splash. Fuel came out of the vent. I looked at the valves and both were set to the same tank. Just did not make sense. When I looked into it I found one of the valves had gone bad. They should have a definite click when moved from one position to the next. The bad one did not have this click and in fact only the handle and shaft moved, but not the ball.

The squeeze bulb in line before the Racors is probably the best for the money modification I have done to my boat. Sure makes life easy.

Valves, valves, valves, everywhere.* Just a sample.

Thanks guys for all you input.

Anode; I don't think that is the case. The fuel polishing guys took the fuel sending units out of each tank and pumped the fuel back into the filler port. I observed them so I'm not concerned about swaped lines.

SaltyDog, you just might be on to something there. The 2 valves I have, one for each engine are of the ganged type, IOW there are 3 ports in 2 rows all on the same stem. The front row manages fuel* supply and are attached to thicker lines while the aft row manages return fuel and those ports are connected to slightly thinner lines. With these ganged valves its not possible to return fuel to any tank other than the one it is drawn from.........unless the valve broke!

I do not get a click on either valve when it is moved. The handle and of course the valve stem that it is connected to moves 180 deg and can be left in any position. IMO this is a poor design due to the fact very horrible conditions will quickly develop if the handle is not in one of the proper positions. I always shutdown the engine prior to moving a fuel selection valve. Prior owner didn't and it cost him a fuel cooler.

I'm going to find out who the manufacturer of the valve is Monday and have a talk with him.

But, I'll be surprised if that is the problem. I'm still thinking that there is something I did that is causing this issue.

I installed squeeze bulb priming after a spat with bad fuel. Trying to pore fuel into a racor while the boat is rocking back and forth is just loads of fun.

Mark; now admit it, you just installed some of those valves to look cool. BTW, they make valves with much shorter handles.

*


-- Edited by timjet on Saturday 30th of April 2011 08:58:34 PM

timjet wrote:
Mark; now admit it, you just installed some of those valves to look cool. BTW, they make valves with much shorter handles.

*

Click to expand...

*But I like the leverage!

Tim IIRC the opening will be where the pointer on the handle points (short end). It is not where the handle points. Your photo looks to be pointing to the Aux tank.

Yes that's true, you have to look at it closely.

Well I figured out the problem, 5 days before we left for our Key West cruise. The ganged valve failed and was porting return fuel to the wrong tank. I took the 3 hoses from the return side of the valve and plumbed in a new 2 way valve and it works. It's a bastardized effort, but it got us to Key West and back with no issues. I'll replace the ganged valve with another 2 way valve.*