From: James Shanks (n1vbn@bit-net.com)
Date: Mon Feb 16 2004 - 02:20:08 PST
Ok Caleb,
Why are you making things more complex? Do it the way Diesel truck
with two or more tanks have done it for over 50 years with very little
problem. You can use the old system aka: a gravity feed system from the
auxiliary tank to the primary tank which feeds the engine. Both tanks must
be mounted on the frame at the same level. The gravity transfer line is
mounted at the lowest point of the fuel tanks and runs in a straight line
to the other tank be sure to use shutoff valves in each fuel tank in case
the transfer line is broken. There are generally plugged fittings where the
transfer line attach at either the end of the tank or in the middle of the
bottom of the tank. Replace the plugs with shutoff valves.
Its only in the last 5 years or so that the civilian trucking
world went to a split fuel system aka it feeds off both tanks
simultaneously and the fuel return is split between both tanks. The
advantage of the split return system is even though you don't fill both
tanks full it evens each tank out with out the possibility of something
catching the transfer gravity line and ripping it and causing a spill.
If you have a good fuel level gauge and it sounds like you do go
back to single feed from the right tank to the fuel injection pump and use
a single line to feed from the left hand tank to the right hand tank with a
manually operated switch inside the truck controlled by the driver. As long
as the fuel fill cap is on and correctly mounted with a good gasket you
route the right vent line to the left tank return fitting which will the
vent the right tank when not transferring fuel. Run the transfer pump when
you see 1/4 tank on the right side and shut it off when it reads 3/4.
James Shanks
n1vbn@arrl.net
1998 IMZ 8.103
1984 HD FLHT-C
At 03:07 PM 2/15/2004, Bill & Bonnie Prestin wrote:
> I hope Caleb's SVO fuel system is successful. It is good to think the
>system through before making the conversion. The plumbing is very important
>for it to all work right.
>
>I'll tell about what I have been experiencing with my dual diesel tanks.
>
> I have a dual tank setup on my deuce. I have been having some very!
>annoying difficulties with the plumbing of the system. My system is
>controlled by a switch on the dash that operates a relay which controls
>switching of the in tank fuel pumps and in tank level sensors for the fuel
>gage. When I switch to the left tank it runs the left fuel pump and uses the
>left level sensor, etc. I have had some difficulty locating any 24 volt fuel
>solenoids that don't need a significant differential pressure to operate. So
>the way I set up the system is, the fuel coming from the fuel pumps goes
>through check valves then connect together into a single line and goes to
>the engine. That way whichever tank is selected is the one that supplies the
>engine, but it cannot back-feed into the other tank because of the check
>valves. The returns go through a manual selector valve to select the tank to
>return the overflow fuel (from the engine) to.
> The problem I have is, the check valves operate on such low pressure
>that they keep getting stuck and send fuel from one tank into the other.
>This tank then overflows. I had to reroute the tank ventilation system
>because the first time it happened fuel filled the other tank, then pushed
>up into the trucks entire vent system putting diesel into the engine
>crankcase, air cleaner, all gear boxes, break system, etc. I then lost a rod
>bearing and when trying to back it down a slope into the shop, excess fuel
>dumped out of the air cleaner into the engine and it ran away (the engine
>ran away) and I thought it would explode. I pulled the engine stop lever and
>ran for it. Luckily, the truck coasted onto level ground, and the engine
>stalled when it ran out of fuel.
> I have since drained all fluids and replaced them. I had to pull the
>engine and replace it also. I routed the vent system with the fuel tanks
>separate from all the others. I cleaned out the stuck check valve, and
>thought I had solved the problem. (not!) It happened again and I lost some
>diesel out the separate vent line and could only use one tank for the
>remainder of the trip.
>
> What I would like to do is eliminate the check valves and manual return
>valve altogether. I would like to install two 24 volt fuel selector valves
>to route the supply and return fuel lines automatically when I switch the
>selector switch on the dash. Does anyone know of any fuel selector
>valve/solenoids that operate on 24 volts DC and that don't need a high
>differential (pilot)pressure (I think the in tank pumps provide less than 15
>lbs, probably 5 to 7 lbs pressure) Anyone know? I would prefer very high
>quality ones with metal fittings if I can find them. Everything I have seen
>is the cheap plastic 12 volt ones for modern trucks.
>
>Any ideas anyone!!
>
>Caleb?
>
>Bjorn??
>(you seem to be able to find or make just about anything!)
>
>Thanks,
>Bill
>Michigan
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