Dual tanks

[AllanD]

Isnt the fuel return controlled by fuel pressure? Couldn't you run a pressure driven line that t's off into both tanks, once one tank is full it would feed the other line. Gravity and path of least resistance and all? I know Im thinkin relatively simple but didnt all great complicated thing(atom bomb) start with sumthin relatively simple? (firecrackers- gun poweder and duct tape)

That would work great, until:
a) one or the other of your fuel pumps "Died" on a long trip
b)You get a "bad" batch of gas
c)One tank springs a leak

and in any of those case you'd basically be pumping half your
fuel into a problem...

And what's worse when it did work "correctly"
(presuming 20gallon tanks and 20mpg) you'd get 400 miles
out of whichever tank you used first, then however many miles it took to pump half the return fuel into the otherwise empty tank, so you'd find yourself switching back and forth to "find" where the fuel was
in ever decreasing time intervals...

And eventually fuel or not one of the pumps would lose prime
even with fuel in the tank....

are you seeing this as a bad idea yet?

Or do I need to continue?

I'm personally "annoyed" with my current system because
it's still prone to a "single point failure", the selector valve itself.

and it has split an internal O-ring once that resulted
in me blowing 12gallons of $4/gallon fuel overboard.

MY rear tank being out of a 1993 F450 has that internal
cannister assembly, my front tank has an essentially stock
1994 Ranger Supercab sender unit. I really need to make up
an F-series type cannister pump assembly for the front tank
because then I could eliminate the selector valve entirely.

But that has it's own issue, the pressure driven return valve
built into the cannister is prone to failure as is the non return
valve built into the pump itself.

witness that there was a "Recall valve", an inline check valve,
that needed to be added to all 1992-1997 F-series trucks
with dual tanks to prevent the in-use tank's pump from blowing fuel (backwards) through the standby fuel tank's pump.

So there were basically three different schemes that
ford used for switching between tanks on EFI trucks
and each has it's advantages and disadvantages, yet
there is still not a "perfect" system that can be created
from the exsisting pieces.

I will observe that when my front tank is nearing empty I get
momentary fuel starvation issues as the fuel sloshes away
from the pickup, yet when it's really empty I can literally mop out the remaining fuel with a couple of paper towels.

when the engine stutters from fuel starvation on the rear tank
on anything other than a steep upgrade it's really empty.

I'm using the motorized six-port selector valve common to
all EFI Rangers and Econlines.
It's very compact, reasonably reliable and all the internal seals
are simple O-rings (No failure prone diaphrams!)

unlike the other valves it DOES positively select tank and return feed.
Power switching to the in-tank pumps is accomplished by the dash mounted switch while the guages are switched by the selector valve.

the thing that makes me most nervous about my combination
is that in the event the selector valve fails and the pump gets
switched to the other tank anyway the fact that I am running
high pressure in-tank pumps means that I can potentially blow
the valve apart.

I believe my recent O-ring failure was due to the extra strain
placed on the O-ring by a high pressure pump on one side
and a clogged fuel filter on the other.

I could eliminate that hazard by simply bypassing the valve
on the high pressure side and feed from the pumps to engine
via a simple "Y" with "recall" check valves on each in-tank
pump assembly. thus the selector valve would only control
return fuel and the guage senders

that's probably what I'll do, as it'll positively control against
cross-feeding the returns while not subjecting the selector
valve's high side to pressure to which it was not designed to handle.

AD

 

[koda6966]

Hey AllanD... you wouldn't happen to know what that option for the bigger tank on rangers was called, and how big the larger one was.. do you?

 

[feellnfroggy]

That would work great, until:
a) one or the other of your fuel pumps "Died" on a long trip
b)You get a "bad" batch of gas
c)One tank springs a leak

and in any of those case you'd basically be pumping half your
fuel into a problem...

And what's worse when it did work "correctly"
(presuming 20gallon tanks and 20mpg) you'd get 400 miles
out of whichever tank you used first, then however many miles it took to pump half the return fuel into the otherwise empty tank, so you'd find yourself switching back and forth to "find" where the fuel was
in ever decreasing time intervals...

And eventually fuel or not one of the pumps would lose prime
even with fuel in the tank....

are you seeing this as a bad idea yet?

Or do I need to continue?

I'm personally "annoyed" with my current system because
it's still prone to a "single point failure", the selector valve itself.

and it has split an internal O-ring once that resulted
in me blowing 12gallons of $4/gallon fuel overboard.

MY rear tank being out of a 1993 F450 has that internal
cannister assembly, my front tank has an essentially stock
1994 Ranger Supercab sender unit. I really need to make up
an F-series type cannister pump assembly for the front tank
because then I could eliminate the selector valve entirely.

But that has it's own issue, the pressure driven return valve
built into the cannister is prone to failure as is the non return
valve built into the pump itself.

witness that there was a "Recall valve", an inline check valve,
that needed to be added to all 1992-1997 F-series trucks
with dual tanks to prevent the in-use tank's pump from blowing fuel (backwards) through the standby fuel tank's pump.

So there were basically three different schemes that
ford used for switching between tanks on EFI trucks
and each has it's advantages and disadvantages, yet
there is still not a "perfect" system that can be created
from the exsisting pieces.

I will observe that when my front tank is nearing empty I get
momentary fuel starvation issues as the fuel sloshes away
from the pickup, yet when it's really empty I can literally mop out the remaining fuel with a couple of paper towels.

when the engine stutters from fuel starvation on the rear tank
on anything other than a steep upgrade it's really empty.

I'm using the motorized six-port selector valve common to
all EFI Rangers and Econlines.
It's very compact, reasonably reliable and all the internal seals
are simple O-rings (No failure prone diaphrams!)

unlike the other valves it DOES positively select tank and return feed.
Power switching to the in-tank pumps is accomplished by the dash mounted switch while the guages are switched by the selector valve.

the thing that makes me most nervous about my combination
is that in the event the selector valve fails and the pump gets
switched to the other tank anyway the fact that I am running
high pressure in-tank pumps means that I can potentially blow
the valve apart.

I believe my recent O-ring failure was due to the extra strain
placed on the O-ring by a high pressure pump on one side
and a clogged fuel filter on the other.

I could eliminate that hazard by simply bypassing the valve
on the high pressure side and feed from the pumps to engine
via a simple "Y" with "recall" check valves on each in-tank
pump assembly. thus the selector valve would only control
return fuel and the guage senders

that's probably what I'll do, as it'll positively control against
cross-feeding the returns while not subjecting the selector
valve's high side to pressure to which it was not designed to handle.

AD

OK so at first I was irritated because some of your answer came across as sounding a little rude, but moving past that you have alot of good information and brought up a buncha good points, which in turn made me realize sumthing else.....


Alot of my mustang buds, (10 different sites) tend to take the 3.8l return style fuel systems and make them returnless. Why is this not an option with our rangers? wouldn't a returnless system be a benefit and makethe second tank option alot more viable and workable?

 

[AllanD]

converting to returnless?
that can only work because later 3.8 (split port) mustangs were made as "Returnless" fuel systems and there is some rediculous notion in the mustang community that if you don't have all the factory "tweeks" (that usually aren't performance related) you are missing out on something.


10 years ago guys were stiill converting Speed density 5.0's to Mass air, because of a FALSE belief that mass air was superior.
If you leave our mustang stock there is noneed, and if you "Tweek" things the Speed Density is actually EASIER to mess around with. and the mass air meter you don't have can't fail.

In point of fact the change was irrelevant to performance and reliability. well... except for the basic engineering truth that the more complicated something is the more possibility of failure that exsists.

Basically the returnless system regulates fuel pressure by rapidly
switching power to the pump on and off, instead of "dumping"
unneeded fuel back to the tank.

the reason for returnless fuel systems?

Fuel that is first pumped with a rotary roller fuel pump is heated slightly by the pump.
Second the fuel then goes up to the engine and into the fuel rail
the fuel rail is mounted to a hot engine where the fuel is heated further.

Then some of the fuel is dumped back to the tank, gradually as the engine is run ALL the fuel in the tank is slowly circulated through the pump, filter and fuel rail before it is returned to the tank... this tends to warm the entire mass of fuel in the tank....

BTW, when driving or idling the entire 20gallons in the fuel tank will be pumped through the filter and rail about once ever 35-40min, more rapidly thereafter as the supply of fuel shrinks via consumption.

I can already hear you thinking the correct answer as to why the
changed things... increased evaporative emmissions from the heated fuel...

Not only does it require an EEC5 computer to control the fuel pump differently, but the sensor that actually looks at the fuel pressure, and the wide band oxygen sensors that monitor exhaust composition...

You are simply trading more complication in a new area for a little complication where you started off working.

IF my guessing above is wrong the mustang guys are doing it differently and then they are in uncharted territory.

Basically the returnless fuel systems require computer control that most Ranger engines before the 4.0SOHC don't have.

Returnless appeared on the first ford vehicles in '99 or '00
Kinda tough to adapt it into my '87 with a 93 engine even if I was interested in doing it. (you can take it I'm not interested)

I like things simple, but there is simplicity and false simplicity
(aka hidden complexity)

Hey AllanD... you wouldn't happen to know what that option for the bigger tank on rangers was called, and how big the larger one was.. do you?

Which option?

On the supercabs used three different fuel tanks between 1985 and 1997

'85-87 a metal 14.5gallon tank was used
'89-90 a 17gallon plastic tank was used.
'90-1/2 through 1997 a 21-ish gallon tank was used.

Though the official capacity was changed as often as some engineers change their underwear and thus you can claim any capacity between 20gal and 22gallons I have personally pumped 24.5gallons into one from a metered pump I trust. (absolutely topped off)

AD

 

[AllanD]

why cant a shortbed tank be mounted backwards on the other side opposite teh current tank,?

This is impossible due to the irregular shape of the tank

the tank isn't a simple retangular box

It's vaguely wedge shaped and actually extends under the cab.

AD

 

[koda6966]

Which option?
On the supercabs used three different fuel tanks between 1985 and 1997
'85-87 a metal 14.5gallon tank was used
'89-90 a 17gallon plastic tank was used.
'90-1/2 through 1997 a 21-ish gallon tank was used.
Though the official capacity was changed as often as some engineers change their underwear and thus you can claim any capacity between 20gal and 22gallons I have personally pumped 24.5gallons into one from a metered pump I trust. (absolutely topped off)
AD

I somehow managed to get 25 and some change into mine. I trust the pump as well, its a privately owned gas station by my cousins erm.. "guardian". Maybe its just a tank anomaly?

 

[AllanD]

Well... My tank has some small strategically drilled holes in certain parts of the veht system that allows me to fill most or all of the "Expansion space"

What SHOULD be vapor space in my main tank can be filled with fuel

AD

 

[koda6966]

Well... My tank has some small strategically drilled holes in certain parts of the veht system that allows me to fill most or all of the "Expansion space"

What SHOULD be vapor space in my main tank can be filled with fuel

AD

Maybe a P.O. did that to my tank as well? It's so confusing.. oh well, shouldn't complain about bigger tanks.