Fuel Return Switch Question
Thread Starter
|
New User
Joined: Mar 2011
Posts: 2
Likes: 0
Fuel Return Switch Question
Hi there, This is my first post, likely not my last.
I don't have a whole hell of a lot of experience with engines of any sort, so you may have to bear with me if my questions are too low-brow or anything.
Anyway, I've got a 1990 7.3 E350 Diesel Van with two tanks and a built-in tank selector.
My question is this: Say I've been running the engine on fuel from tank A. When I switch to Tank B, is any fuel from Tank A being sent via the return lines to Tank B now? Or does the fuel return to the tank it came from?
I'm trying to figure out if I can keep the two fuel supplies from finding their way into the other tank.
Thanks for the help.
I don't have a whole hell of a lot of experience with engines of any sort, so you may have to bear with me if my questions are too low-brow or anything.
Anyway, I've got a 1990 7.3 E350 Diesel Van with two tanks and a built-in tank selector.
My question is this: Say I've been running the engine on fuel from tank A. When I switch to Tank B, is any fuel from Tank A being sent via the return lines to Tank B now? Or does the fuel return to the tank it came from?
I'm trying to figure out if I can keep the two fuel supplies from finding their way into the other tank.
Thanks for the help.
Thread Starter
|
New User
Joined: Mar 2011
Posts: 2
Likes: 0
Thanks for the replies.
I guess my followup question is, how is that regulated? Are the supply and return lines on separate circuits? Is it possible that unburned fuel that is in the engine when I switch is going to end up in the other tank?
Pardon me if these are stupid questions. I don't want to waste anybody's time if they are.
I guess my followup question is, how is that regulated? Are the supply and return lines on separate circuits? Is it possible that unburned fuel that is in the engine when I switch is going to end up in the other tank?
Pardon me if these are stupid questions. I don't want to waste anybody's time if they are.
Tuned
Joined: Feb 2006
Posts: 487
Likes: 3
From: Lampasas,TX
The valve on my frame has 4 lines coming in (a supply line and a return line to each tank) and 2 lines going out ( a supply line and a return line to the engine). I'm sure that whenever I switch tanks whatever fuel is in the return line between the engine and the valve will be returned to the tank I just selected regardless of which tank it came out of. However the return line is only 5/16" diameter so even if there is 6' of return line between the engine and the valve how much fuel does it hold- 1 pint maybe?
Fleet Owner
Joined: Jul 2006
Posts: 20,377
Likes: 845
From: Mi'kma'ki
there is a fuel selector valve down on the frame rail.
it has 6 ports.
2 ports for each tank.
tank one= line out into FSV.line in from FSV.
tank two= line out into FSV.line in from FSV.
FSV to engine=one line out and one return.
its electronically controlled via the switch on the dash.
once you switch tanks,the fuel in the line from FSV to engine,and the return back to the FSV is still full of fuel,so this fuel in the line/full fuel filter will now return the selected tank instantly.
diesel fuel tank one.
alternative fuel tank two.
start the truck on tank one,switch to tank two,the diesel in the lines and filter will return into tank two.
run tank two,and switch back over to tank one to empty the line/filter for easier cold start next time,and tanks two fuel line/filter is returned into tank one.
the more you switch back and forth,naturally the more diluted your mixes will be in the tanks.
it takes a few minutes to empty the filter and line.so give yourself plenty of time to switch back to diesel before shut down.
approx 2 miles from home is when id switch back over.
it has 6 ports.
2 ports for each tank.
tank one= line out into FSV.line in from FSV.
tank two= line out into FSV.line in from FSV.
FSV to engine=one line out and one return.
its electronically controlled via the switch on the dash.
once you switch tanks,the fuel in the line from FSV to engine,and the return back to the FSV is still full of fuel,so this fuel in the line/full fuel filter will now return the selected tank instantly.
diesel fuel tank one.
alternative fuel tank two.
start the truck on tank one,switch to tank two,the diesel in the lines and filter will return into tank two.
run tank two,and switch back over to tank one to empty the line/filter for easier cold start next time,and tanks two fuel line/filter is returned into tank one.
the more you switch back and forth,naturally the more diluted your mixes will be in the tanks.
it takes a few minutes to empty the filter and line.so give yourself plenty of time to switch back to diesel before shut down.
approx 2 miles from home is when id switch back over.
i ain't rite
Joined: Mar 2005
Posts: 65,564
Likes: 5,601
From: Marlboro Mental Hospital.
the answer to what i think is going to be your next question is, yes the fuel selector switch can go bad and draw fuel from one tank , but always return fuel to the other tank. it happens quite often.
Thread
Thread Starter
Forum
Replies
Last Post
FMC_Convert
General Diesel Discussion
8
Jul 13, 2013 09:14 AM
1FastGambler
1973 - 1979 F-100 & Larger F-Series Trucks
5
Oct 20, 2011 06:11 PM
eatont9999
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
9
Sep 18, 2011 06:42 PM
predaina
1987 - 1996 F150 & Larger F-Series Trucks
29
Mar 29, 2011 07:07 PM
whimsy
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
1
Jan 12, 2008 09:40 AM
