Fuel tank crossover line question

Mike_M · Sep 29, 2020

DennisB1 said:
To me you should have a separate lines for each engine from each tank. In your current installation you could have a single failure issue (i.e, air leaking into the manifold feeding both engines) that would shut down both engines. Loosing both engines at the same time could be dangerous. As mentioned earlier vacuum gages would help determine if you have issues with flow/pressure drop. The pressure drop in the line engine side of the filters should be less than several psi below ambient pressure at maximum engine flows. If you have a tank shutoff valve you could rig a hand operated vacuum pump at the engine side and see if you have leakage into the line. Something to do at the dock with out engines running.

Have you changed the o'ring seals on the Racors along with the filters the cap and screw handle can leak air if the seals are bad and you have a fair amount of suction pressure.

A comment it appears in you picture of the cross over line that its PVC plastic (gray color tube about 1.5 to 2 inch diameter).
The cross over should be closed and used at the dock for balancing the tanks if the sight gages show a difference in fuel height. Other wise they should be closed during operation and as note be others should have no impact of operation closed.

Hi Dennis,
Thanks for the input. I agree, having a separate manifold(s) for each side only makes sense. I originally closed the crossover valve and suddenly lost both Mains and my Jenny. My original suspicion was that the crossover had caused the problem with possibly a venting problem with tanks balancing and everything running at load. I now believe that my manifold filled with crud and have not had a problem since cleaning/blowing manifold and lines. Ordered gauges and waiting to confirm.

btw - the crossover is stand pipe with ancient gate valves, that's project #2, thanks again

Mike_M · Sep 29, 2020

Another reason to add a transfer pump, I love that idea versus them dragging another hose across the deck, thanks for the input.

dhays said:
FWIW, I only have a single engine and the fuel system is as it was when I bought the boat. I have a fuel manifold that controls which tank fuel is drawn from and to which tank fuel is returned. The Genset and diesel furnace are not included in that.

I also have a cross line with a transfer pump. It is not necessary, but I find I really like it. It is easy to balance the fuel using it. It can also be very convenient. I usually will transfer most fuel to the Port tank before refueling and then fill up the starboard tank. I normally don't need to have all 400 gallons of fuel, so doing this I end up with about 250-300 gallons of fuel which lasts me a long time.

Mike_M · Sep 29, 2020

Agree, you are absolutely correct. I now believe that the manifold was the culprit causing total loss of power. I've cleaned / blew out all the lines and removed the crud from the manifold. And yes, it was very dangerous and scarry as I was in 40 mph winds scrambling down in the engine room. After using the manual primers on my engines, she started back up and we were out of harm's Way. It has not happened since but I am very excited to implement my new fuel system. Thanks for the input

DennisB1 said:
To me you should have a separate lines for each engine from each tank. In your current installation you could have a single failure issue (i.e, air leaking into the manifold feeding both engines) that would shut down both engines. Loosing both engines at the same time could be dangerous. As mentioned earlier vacuum gages would help determine if you have issues with flow/pressure drop. The pressure drop in the line engine side of the filters should be less than several psi below ambient pressure at maximum engine flows. If you have a tank shutoff valve you could rig a hand operated vacuum pump at the engine side and see if you have leakage into the line. Something to do at the dock with out engines running.

Have you changed the o'ring seals on the Racors along with the filters the cap and screw handle can leak air if the seals are bad and you have a fair amount of suction pressure.

A comment it appears in you picture of the cross over line that its PVC plastic (gray color tube about 1.5 to 2 inch diameter).
The cross over should be closed and used at the dock for balancing the tanks if the sight gages show a difference in fuel height. Other wise they should be closed during operation and as note be others should have no impact of operation closed.

slymeso44 · Sep 30, 2020

i HAVE A 42 JEFFERSON SUNDECK WITH THE EXACT SAME*FUEL SYSTEM AND MY CROSS OVER ARE ALWAY OPEN , ALL THEY DO IS LEVEL THE FUEL BETWEEN THE TWO TANK, YOUÈR HAING OTHER ISSUE , YOUR MANIFOLD MAYBE CONTAMINATED AND PARTIALY BLOCK OR YOUR FUEL LINE, BREAK THE FITTING AT ONE OF YOUR MANIFOLD SUPPLY AND CHECK THE CONDITION OF YOUR LINE

Mike_M · Oct 1, 2020

Thanks for the input. Yes, after all the troubleshooting it appears that my manifold had gotten some crud and since I've cleaned it and blown out all my lines, I've not had any other issues. She is now back up and running, thanks for your help.

slymeso44 said:
i HAVE A 42 JEFFERSON SUNDECK WITH THE EXACT SAME*FUEL SYSTEM AND MY CROSS OVER ARE ALWAY OPEN , ALL THEY DO IS LEVEL THE FUEL BETWEEN THE TWO TANK, YOUÈR HAING OTHER ISSUE , YOUR MANIFOLD MAYBE CONTAMINATED AND PARTIALY BLOCK OR YOUR FUEL LINE, BREAK THE FITTING AT ONE OF YOUR MANIFOLD SUPPLY AND CHECK THE CONDITION OF YOUR LINE

SteveK · Oct 1, 2020

Mike_M said:
Thanks for the input. Yes, after all the troubleshooting it appears that my manifold had gotten some crud and since I've cleaned it and blown out all my lines, I've not had any other issues. She is now back up and running, thanks for your help.

Mike, glad you found your problem.
How did the crud get into the manifold?
Is the manifold direct from the tanks and not first through the racor pictured at the tank?

Mike_M · Oct 1, 2020

The lines go straight from the tanks to the manifold and then to the racors. I think the tank stirred up the crud in the bottom of the tanks as I'd been out in some rough weather a couple days before then. I'd like to put a mud filter in between the tank and manifold, do you think just another racor would work?

Soo-Valley said:
Mike, glad you found your problem.
How did the crud get into the manifold?
Is the manifold direct from the tanks and not first through the racor pictured at the tank?

SteveK · Oct 1, 2020

I recall seeing two beside tank. Why not plumber tank into those and then to manifold

Mike_M · Oct 2, 2020

Soo-Valley said:
I recall seeing two beside tank. Why not plumber tank into those and then to manifold

The racors are forward in the engine room and my manifold is at the AFT bulkhead. I think it would be easier just to plug in a set of filters

Fuel tank crossover line question

Mike_M

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