Fuel tank crossover line question

Mike_M · Sep 19, 2020

Hi all, I have a Jefferson 45 and have attached the photo of my fuel set up. When underway with both crossover valves port and starboard open, I lose fuel to both Mains and the generator due to starvation. After I close the starboard crossover valve and prime the engines, she fires up and everything runs great. I've read many post of folks indicating that you should run with the crossover lines open but when I seem too, I find myself down in the engine room using the manual primers to reprime. Any input would be greatly appreciated.

Redhook98 · Sep 19, 2020

Are your fuel tank vents working correctly? Next time try it with your fuel caps off your tanks.

sunchaser · Sep 19, 2020

Mike
How difficult would it be to set up a return manifold? This way the engines and genset would return to the single tank you're drawing from. I've never liked crossovers as part or the normal operation. Mine have been shut since the boat was new.

Do the tanks have sight tubes?

SteveK · Sep 19, 2020

Your drawing shows how flows should be. I would like to see a picture of the manifold? or the valve setup which shows direction of flows too.

after I close starboard valve, prime it starts
Do you then leave it closed?

Mike_M · Sep 19, 2020

I'll try it but I'm going to need to find another crew member as my wife does not like it when the boat dies out on the water... there's no statement like telling her that I swear I can get it started again, LOL

Mike_M · Sep 19, 2020

I'll try it but I'm going to need to find another crew member as my wife does not like it when the boat dies out on the water... there's no statement like telling her that I swear I can get it started again, LOL

Redhook98 said:
Are your fuel tank vents working correctly? Next time try it with your fuel caps off your tanks.

Mike_M · Sep 19, 2020

sunchaser said:
Mike
How difficult would it be to set up a return manifold? This way the engines and genset would return to the single tank you're drawing from. I've never liked crossovers as part or the normal operation. Mine have been shut since the boat was new.

Do the tanks have sight tubes?

Yes. The valve to the left in the picture is for the bottom vent for Sight glass and the valve to the right is the crossover valve

Mike_M · Sep 19, 2020

Soo-Valley said:
Your drawing shows how flows should be. I would like to see a picture of the manifold? or the valve setup which shows direction of flows too.

after I close starboard valve, prime it starts
Do you then leave it closed?

I can visibly Trace all the lines.

Mike_M · Sep 19, 2020

Mike_M said:
I can visibly Trace all the lines.View attachment 108000 View attachment 108001

sunchaser said:
Mike
How difficult would it be to set up a return manifold? This way the engines and genset would return to the single tank you're drawing from. I've never liked crossovers as part or the normal operation. Mine have been shut since the boat was new.

Do the tanks have sight tubes?

I don't really care for the crossover option when running dual props. The fuel manifold allows me to switch tanks to keep balanced but it's never been a concern.

Mike_M · Sep 19, 2020

And yes, I leave it closed.

Soo-Valley said:
Your drawing shows how flows should be. I would like to see a picture of the manifold? or the valve setup which shows direction of flows too.

after I close starboard valve, prime it starts
Do you then leave it closed?

Comodave · Sep 19, 2020

I have never opened the crossover valve on my boat. Port engine and genset run on port tank and starboard engine runs on starboard tank only. Returns go to tank supplying the engine.

SteveK · Sep 19, 2020

Mike_M said:
And yes, I leave it closed.

Then I suggest that the starboard tank feed line is drawing air.

BTW is the crossover direct from tank bottom to tank bottom or is run through the top two inlets of manifold.

Mike_M · Sep 19, 2020

Soo-Valley said:
Then I suggest that the starboard tank feed line is drawing air.

BTW is the crossover direct from tank bottom to tank bottom or is run through the top two inlets of manifold.

Thanks so much for all of the responses .

What's interesting is, I can have the boat idle for 30 minutes plus with the Genny running and then put a load and she starves out. Would you suspect that my vents may be clogged? at idle, it's not drawing as much fuel but if the vents are clogged maybe it's too much for my system when under load.

Also, would there be any harm in closing both crossover valves as I have the port open and the starboard shut and she runs fine. I left it this way as I loss both engines in 12 foot seas. At that time, I just closed the starboard cross-over valve and re-primed the mains as it was quite the Panic moment. My initial thought was, I could not have all three systems pulling from the tanks and also transferring fuel as it was too much for the system. Then, I started thinking maybe my vents would be clogged.

The crossover is direct from tank to tank.

Mike_M · Sep 19, 2020

Comodave said:
I have never opened the crossover valve on my boat. Port engine and genset run on port tank and starboard engine runs on starboard tank only. Returns go to tank supplying the engine.

I'm not a fan either but I'm thinking that I may be able to fill both tanks from one side if the fuel dock doesn't have dual pumps available. I guess these were plumbed when the boat was built in the event somebody were to be on the hook and using a lot of fuel for the Jenny and the stability issue

Giggitoni · Sep 19, 2020

Redhook98 said:
Are your fuel tank vents working correctly? Next time try it with your fuel caps off your tanks.

I think this ^ should be the next thing to investigate. Look for mud wasps within an inch or two from your tank vent openings on the side of your hull. Next time you’re out, as Redhook suggests, leave your fuel caps off (maximum tank venting) and run the rpm up to cruise setting.

SteveK · Sep 19, 2020

Mike_M said:
Thanks so much for all of the responses .

What's interesting is, I can have the boat idle for 30 minutes plus with the Genny running and then put a load and she starves out. Would you suspect that my vents may be clogged? at idle, it's not drawing as much fuel but if the vents are clogged maybe it's too much for my system when under load.

Also, would there be any harm in closing both crossover valves as I have the port open and the starboard shut and she runs fine. I left it this way as I loss both engines in 12 foot seas. At that time, I just closed the starboard cross-over valve and re-primed the mains as it was quite the Panic moment. My initial thought was, I could not have all three systems pulling from the tanks and also transferring fuel as it was too much for the system. Then, I started thinking maybe my vents would be clogged.

The crossover is direct from tank to tank.

Then the cross over is not causing your problems, IMO. Edit: You have the starboard cross over shut and port open should only affect the the crossover, not fuel to engines! I thought you closed the fuel in to manifold from starboard.

Original problem was you had to close the starboard feed and prime to restart and then both engines ran with only port feed.

You now say both engines and genny idle for 30 minutes and then starve when put under load. Is this with only the port open?

Or is from the original post with both starboard and port open?

Mike_M · Sep 19, 2020

Giggitoni said:
I think this ^ should be the next thing to investigate. Look for mud wasps within an inch or two from your tank vent openings on the side of your hull. Next time you’re out, as Redhook suggests, leave your fuel caps off (maximum tank venting) and run the rpm up to cruise setting.

Agree, that is at the top of the checklist. What's weird is when I close the starboard cross-over valve, the boat runs great. I guess the additional transfer of fuel is the hinging point for the lack of ventilation

Mike_M · Sep 19, 2020

Soo-Valley said:
Then the cross over is not causing your problems, IMO.

Original problem was you had to close the starboard feed and prime to restart and then both engines ran with only port feed.

You now say both engines and genny idle for 30 minutes and then starve when put under load. Is this with only the port open?

Or is from the original post with both starboard and port open?

Sorry for the confusion... the port crossover is open and with the starboard crossover closed, the boat runs fine. If I open both crossover valves so that the tanks balance out, it starves under load.

SteveK · Sep 19, 2020

Mike_M said:
Sorry for the confusion... the port crossover is open and with the starboard crossover closed, the boat runs fine. If I open both crossover valves so that the tanks balance out, it starves under load.

No worries. More confused now. A direct line crossover from tank to tank should not be causing the problems you have described whether one or both taps are open or closed. All the crossover does is level the fuel.

SoWhat · Sep 19, 2020

Crossovers are not essential. Mine is closed.
In addition to a vent check, I would inspect all of the copper fuel tubing. If one line has a kink, it could restrict fuel flow. (Although that doesn't explain all engine scenario)

sunchaser · Sep 19, 2020

Mike
Do you have a primary filter for each engine? Where are they located?

Mike_M · Sep 19, 2020

Yes, I've inspected all lines and everything seems to be without fault. The coincidence with closing the valve and being able to re Prime and continue on my way is boggling. I plan on getting underway tomorrow for a vent test as there is no problem at idle, thanks for the respone

SoWhat said:
Crossovers are not essential. Mine is closed.
In addition to a vent check, I would inspect all of the copper fuel tubing. If one line has a kink, it could restrict fuel flow. (Although that doesn't explain all engine scenario)

Comodave · Sep 19, 2020

If one is open and one is closed isn’t it essentially closed? I would think that they would both have to be open in order for fuel to flow. Mine only has 1 valve in the middle of the boat. But I have never opened it because my tanks stay pretty much even, though if I ran the genset a lot they would get out of balance.

Mike_M · Sep 19, 2020

Each one is located by each engine along with sight glass and just above the valves in question

sunchaser said:
Mike
Do you have a primary filter for each engine? Where are they located?

Comodave · Sep 19, 2020

sunchaser said:
Mike
Do you have a primary filter for each engine? Where are they located?

Maybe I missed it but have you changed the filters? That is something I would check just in case. Simple to do.

ABfish · Sep 19, 2020

I've had several issues with vents and insect nests. You don't need to run the boat to test the vents.

I use a cordless shop vac and attach the hose to the outlet of the vacuum, so the vacuum is blowing rather than sucking. Remove your fuel cap and insert the hose in the fuel fill. Turn on the vac. You should feel air exiting the vent.

I would only use this method with tanks the hold diesel fuel. Never with gasoline.

If you have vent problems you should also have issues fueling that tank.

TWille · Sep 19, 2020

Are there any screens in the manifold that are clogged. Perhaps junk on and off the draw tube in the tank?

Mike_M · Sep 20, 2020

Yes, I plan on ensuring that the vents are clear. However, I have insect screens on the vent inlets. At idle, there are no issues. Under way with a load with the crossover valves open, both mains and the Jenny Starve. All indicators are pointing to not being able to transfer while underway.scratching head....

ABfish said:
I've had several issues with vents and insect nests. You don't need to run the boat to test the vents.

I use a cordless shop vac and attach the hose to the outlet of the vacuum, so the vacuum is blowing rather than sucking. Remove your fuel cap and insert the hose in the fuel fill. Turn on the vac. You should feel air exiting the vent.

I would only use this method with tanks the hold diesel fuel. Never with gasoline.

If you have vent problems you should also have issues fueling that tank.

Mike_M · Sep 20, 2020

Since this happened, I have replaced both Rocor`s and secondary filters. Plan on repeating problem scenario and opening fuel fills to see if it's a venting issue. Hoping it's just a matter of not being able to transfer under load which still makes no sense

Comodave said:
Maybe I missed it but have you changed the filters? That is something I would check just in case. Simple to do.

sunchaser · Sep 20, 2020

Mike
Describe the piping run from the tanks to the manifold. Also, the Racor feed line seems to disappear under the tank. You're sure the fuel flow is coming from the manifold?

Is this problem at all related to fuel tank level? Might I suggest ball valves to replace those gates?

I'd suggest a test with a five gallon jerry feeding the Racors. Then you can start working your way back to the tanks to find the obstruction or air leak.

Fuel tank crossover line question

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