Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 22-05-2018, 14:19   #16
Registered User

Join Date: Sep 2007
Location: Queensland, Australia
Boat: None at present--between vessels. Ex Piver Loadstar 12.5 metres
Posts: 1,475
Re: Does diesel fuel return line have to be above fuel tank?

I simply fed mine back to the fuel filter double inlet. Works for me.
Mike Banks is offline   Reply With Quote
Old 22-05-2018, 14:45   #17
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,823
Re: Does diesel fuel return line have to be above fuel tank?

The top of my fuel tanks is at least 42"/1.06m above the top of the engine. Never a problem.
DotDun is offline   Reply With Quote
Old 22-05-2018, 15:41   #18
Registered User

Join Date: Oct 2015
Location: Summerstown Ontario Canada
Posts: 457
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by er9 View Post
want to relocate fuel tank at some point in the future and have been wondering about this recently.

currently fuel tank is uder starboard quarter berth and fuel return line (universal 5432) is mostly above the level of the fuel tank but its only 24" distance from engine to tank. If i were to relocate the tank 10' away under the cabin settee would i have to keep the return line above the level of the fuel tank? is 10' too far a distance for an engine to return un-used fuel back to the tank?

also while im at it...if i decided to add a second fule tank...do i have to have a return line to both tanks or just one? does it really matter?
There is no problem installing a fuel return line below tank level. If you install a second fuel tank, make sure that the tank you draw from has the return line to that tank and not "T" in both tanks. If you draw from one tank, the fuel can and will take the path of least resistance and will draw from one tank and will return to the other and will overfill and will come out the vent. I know! We had a real mess as the vents were on the rear deck on our tugboat and we were pumping over the side when we noticed. If you go double tanks, go double fuel filters double the valves and double you returns and isolate one tank from the other. Since we set up ours that way, allll is very good!!
seabreez is offline   Reply With Quote
Old 22-05-2018, 16:38   #19
Registered User
 
Jacko's Avatar

Join Date: Mar 2011
Location: Far North Queensland Australia
Boat: John Pugh / Currawong 48/OAL
Posts: 205
Re: Does diesel fuel return line have to be above fuel tank?

Just a side note here the fuel going back through the return line has been through your filters so in fact has been " polished " I have often thought that I should look up how much ( litres) fuel passes through this return on my motor so I would know if it is enough to make a difference.
I know that here on the GBR sometimes to get back from up north with the Southern Trades blowing I will have to motor for a couple of days to return to base so large amounts of fuel must go back into the tank.
Any body know how to workout the ratio of fuel used to fuel returned ?

Sorry hope this isn't seen as "HiJacking" the post Cheers Jacko
Jacko is offline   Reply With Quote
Old 22-05-2018, 17:04   #20
er9
cruiser

Join Date: Sep 2014
Boat: 1980 (Canning) Mariner36
Posts: 834
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by seabreez View Post
There is no problem installing a fuel return line below tank level. If you install a second fuel tank, make sure that the tank you draw from has the return line to that tank and not "T" in both tanks. If you draw from one tank, the fuel can and will take the path of least resistance and will draw from one tank and will return to the other and will overfill and will come out the vent. I know! We had a real mess as the vents were on the rear deck on our tugboat and we were pumping over the side when we noticed. If you go double tanks, go double fuel filters double the valves and double you returns and isolate one tank from the other. Since we set up ours that way, allll is very good!!
thanks you pretty much just solidified my decision to go to a single tank instead of two.
er9 is offline   Reply With Quote
Old 22-05-2018, 17:05   #21
er9
cruiser

Join Date: Sep 2014
Boat: 1980 (Canning) Mariner36
Posts: 834
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by Jacko View Post
Just a side note here the fuel going back through the return line has been through your filters so in fact has been " polished " I have often thought that I should look up how much ( litres) fuel passes through this return on my motor so I would know if it is enough to make a difference.
I know that here on the GBR sometimes to get back from up north with the Southern Trades blowing I will have to motor for a couple of days to return to base so large amounts of fuel must go back into the tank.
Any body know how to workout the ratio of fuel used to fuel returned ?

Sorry hope this isn't seen as "HiJacking" the post Cheers Jacko
no worries mate. my question has been answered. i'd like to know as well.
er9 is offline   Reply With Quote
Old 22-05-2018, 19:12   #22
Marine Service Provider

Join Date: Dec 2011
Posts: 1,538
Re: Does diesel fuel return line have to be above fuel tank?

My fuel return line goes from the injector pump to one of the inlet ports on the fuel filter and back to the injector pump. It doesn't go back in the tank. I'm sure someone on this forum will take exception to that but it's worked for twenty years.
jmschmidt is offline   Reply With Quote
Old 23-05-2018, 21:05   #23
Registered User

Join Date: May 2018
Posts: 19
Re: Does diesel fuel return line have to be above fuel tank?

I installed a pair of 4cyl turbo volvos in a 45ft cat a while back. The owner insisted saving by short circuiting the return lines to the suction lines via the
filters on both engines. On ferry run sydney to cairns the tanks down to 30%
and extremly rough weather between newcastle and coffs. Diesel sloshing
and became slightly aerated.Air collected in the filters and one pump siezed.
Other engine missing badly for the same reason. Cat made it to the heavy buoy off SW Rocks. Hung there for rwo days. New pump cost $4500+.Other recovered OK. Needless to say return lines were done correctly.
CORALSEA TRAMP is offline   Reply With Quote
Old 24-05-2018, 00:46   #24
Registered User

Join Date: Jan 2016
Location: San Diego, CA
Boat: Beneteau 40.7
Posts: 343
Re: Does diesel fuel return line have to be above fuel tank?

How about not worrying and just put a tee in the return line from the engine with a line to each tank. The returning fuel would mostly go to the tank selected to supply fuel and in no event would either tank be overfilled. I think the only constraint would be that the tank outside vents should be above any point of the tanks themselves.
thunderhoof is offline   Reply With Quote
Old 24-05-2018, 08:34   #25
er9
cruiser

Join Date: Sep 2014
Boat: 1980 (Canning) Mariner36
Posts: 834
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by thunderhoof View Post
How about not worrying and just put a tee in the return line from the engine with a line to each tank. The returning fuel would mostly go to the tank selected to supply fuel and in no event would either tank be overfilled. I think the only constraint would be that the tank outside vents should be above any point of the tanks themselves.
but what if you were motor sailing for a day or two on a single tack? it seems tank on low side would overfill via gravity. think previous poster said that happened to him and he ended up with fuel coming out his vent lines. of course i could put in a selector valve but now its getting complicated.

decided to keep it simple and just relocate the tank but only use a single tank. i have the space and can actually upgrade from 40 gal tank to 52 gals.
er9 is offline   Reply With Quote
Old 24-05-2018, 10:27   #26
Marine Service Provider

Join Date: Dec 2011
Posts: 1,538
Re: Does diesel fuel return line have to be above fuel tank?

Your problem was they were Volvos, the most complaint ridded power plants in the marine world, as are their cars in the auto world. The car division is owned by the Chinese, don't know if their engine builder is too.
jmschmidt is offline   Reply With Quote
Old 25-05-2018, 15:06   #27
Moderator Emeritus
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by jmschmidt View Post
My fuel return line goes from the injector pump to one of the inlet ports on the fuel filter and back to the injector pump. It doesn't go back in the tank. I'm sure someone on this forum will take exception to that but it's worked for twenty years.


Your biggest issue is heat, often the excess fuel is used as a coolant, by routing it around in a circle it gets hotter each pass through being pressurized to high pressure.
a64pilot is offline   Reply With Quote
Old 25-05-2018, 15:09   #28
Moderator Emeritus
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by Jacko View Post
Just a side note here the fuel going back through the return line has been through your filters so in fact has been " polished " I have often thought that I should look up how much ( litres) fuel passes through this return on my motor so I would know if it is enough to make a difference.
I know that here on the GBR sometimes to get back from up north with the Southern Trades blowing I will have to motor for a couple of days to return to base so large amounts of fuel must go back into the tank.
Any body know how to workout the ratio of fuel used to fuel returned ?

Sorry hope this isn't seen as "HiJacking" the post Cheers Jacko


It is very dependent on engine, and throttle setting.
You can drive yourself nuts trying to figure it out, or you can just disconnect the thing and see how long it takes to fill up a 1 gl container or similar.
Some engines like my baby single cylinder Kubota on my generator returns far more than it burns, I have been told up to ten times as much.
In that case though it only returns 4 gl an hour. So I guess it’s relative also.
a64pilot is offline   Reply With Quote
Old 25-05-2018, 15:35   #29
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,703
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by Jacko View Post
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Any body know how to workout the ratio of fuel used to fuel returned ?

Sorry hope this isn't seen as "HiJacking" the post Cheers Jacko

Honest question: why? All one seems to need to know is fuel consumption for range planning, i.e., how many hours per gallon or litre your engine uses. How much goes into engine use and how much is returned is immaterial. Interesting to know, but useless for real world operation and boat range.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 25-05-2018, 15:42   #30
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,703
Re: Does diesel fuel return line have to be above fuel tank?

Quote:
Originally Posted by thunderhoof View Post
How about not worrying and just put a tee in the return line from the engine with a line to each tank. The returning fuel would mostly go to the tank selected to supply fuel and in no event would either tank be overfilled. I think the only constraint would be that the tank outside vents should be above any point of the tanks themselves.

This is incorrect. It goes against all fuel tank engineering design guidelines. Some earlier respondents have mentioned why, and they are correct, plus a64 noted the heat of returned fuel.


Ask yourself this: How would "...returning fuel would mostly go to the tank selected to supply fuel?" How could this be true? Mostly? Really? If it is an engineered system, one NEEDS to KNOW, not guess.



Also "...and in no event would either tank be overfilled." Simply not true. Let's say tank #1 and tank #2 are BOTH FULL. Tank #1 is being used for the engine, but the return goes back to tank #2. Could you explain what will happen?
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Reply

Tags
diesel, fuel, fuel tank

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Diesel Return Fuel Line Question LA-Sailor Engines and Propulsion Systems 13 23-06-2017 21:45
Diesel Fuel Tank vs Portable Diesel Fuel Cell GaryMayo Engines and Propulsion Systems 11 13-11-2012 15:47
Electric Pump in Fuel Return Line banjoship Construction, Maintenance & Refit 10 12-08-2012 15:56
fuel return line Han Engines and Propulsion Systems 17 17-06-2008 02:58

Advertise Here


All times are GMT -7. The time now is 22:44.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.