Fuel Transfer Pump....

[496 BB]

In process of starting my L18 swap and currently have dual tanks. I know I read somewhere in one of Larrys threads about how the factory transfer pumps wont work for size reasons so was thinking. I plow with this truck so having that extra tank would be nice although it doesnt work now. My idea was as follows:

Get a fuel transfer pump and have the passenger side as the aux tank as it is now. Cap off or just leave in the fuel sending unit and drill a hole to fit a tube down into tank leaving 1/4" from bottom. Weld that to top with it sticking out enough to weld or compression fit a fitting on for the transfer pump. Mount pump on frame or wherever and have it go to main tank. Main tank will have another inlet or I can tap into existing fuel filler hose. Run a switch in cab with some kind of time delay switch as to not leave it on and either overfill or burn up. Also would like to have a manual override for the off position in case it fill up faster than the delay.

Not sure if any of this would work thats why Im wanting some input.

[hatzie]

The stock 1986 should have a mechanical fuel pump with no electric lift pumps in the tanks.
If your new electric fuel pump will pull fuel from the tanks without issues... just plumb it downstream from the tank valve in the main fuel feed line. This leaves the dual tank system basically untouched.


Using a fuel pump to transfer fuel from one tank to the other is asking for trouble.

[DirtyLarry]

Originally Posted by 496 BB

In process of starting my L18 swap and currently have dual tanks. I know I read somewhere in one of Larrys threads about how the factory transfer pumps wont work for size reasons so was thinking. I plow with this truck so having that extra tank would be nice although it doesnt work now. My idea was as follows:

Get a fuel transfer pump and have the passenger side as the aux tank as it is now. Cap off or just leave in the fuel sending unit and drill a hole to fit a tube down into tank leaving 1/4" from bottom. Weld that to top with it sticking out enough to weld or compression fit a fitting on for the transfer pump. Mount pump on frame or wherever and have it go to main tank. Main tank will have another inlet or I can tap into existing fuel filler hose. Run a switch in cab with some kind of time delay switch as to not leave it on and either overfill or burn up. Also would like to have a manual override for the off position in case it fill up faster than the delay.

Not sure if any of this would work thats why Im wanting some input.

Yep, I’m using a transfer pump to run dual tanks in my ’78 K10 with the 8.1L. What I found is the little 5/16 return line through the fuel tank switch valve was too restrictive and drove head pressure up over 100 psi. (The dual tank switch valve is not a problem for little LS engines as they have a smaller return line). I even picked up a brand new GM switch valve only to have the same issue. Without finding any alternatives for a better switch valve I chose to go the transfer route. Eventually, I may do some wiring to have the ECM automatically transfer the fuel like the late model chassis cabs and Suburban’s had with dual tanks where the truck acts like it has one big tank. Corvettes work the same way. The way I have mine currently set up works so well I haven’t had much ambition to go the complicated route.

Here is how mine is set up:

Driver’s tank is the main tank that feeds the engine. It is a ’87 spec TBI tank, ’87 spec TBI sending unit and fitted with an EP381 fuel pump. The EP381 is the 1996/7 Vortec 5.0, 5.7 & 7.4L that supplies 62 psi, which is the same fuel pressure 8.1L and LS engines require.

Passenger’s tank is an ’87 spec TBI tank, ’87 spec TBI sending unit and fitted with an EP241 fuel pump. The fuel pump is wired to a relay powered by a switch in the cab. The original dual tank switch valve is still in place for the sole purpose of being able to flip the switch to see how much fuel is in each tank. The fuel moves from the passenger’s tank over to the driver’s tank and fills the driver’s tank through a T-fitting I added into the fuel filler neck vent. When I first did the 8.1L back in 2008 I was using a Mr. Gasket fuel transfer pump mounted on the frame to "pull" fuel out of the RH tank. That pump was painfully slow so that is why I added a second TBI tank, sending unit with an internal pump. Faster, quieter and more reliable. The only reason I used a EP241 pump is because I had an extra laying around otherwise I would have used a EP381 to match the driver's side plus it probably would push fuel that much faster. The only caveat to this recipe is you must pay attention or you can overfill the tank pretty easily (just like the diesel guys do with their transfer systems) but that could easily be fixed by using a switch with a timer. I drive this truck all over the Southwest and this fuel transfer method works great for me.

This is how the fuel enters the Driver’s side tank (main tank).

Originally Posted by hatzie

Using a fuel pump to transfer fuel from one tank to the other is asking for trouble.

Really, do tell?

[DirtyLarry]

Another thing to consider is if you run a 2004-2010 8.1L returnless type fuel rail the entire return line issues at the tank switch valve is a moot point. I personally don't care for returnless as they do not have adjustable fuel pressure regulators. I love having an adjustable fuel pressure regulator right on the fuel rail. I have both the K10 and '89 Burb with 8.1L's cranked up to around 67 psi.

[hatzie]

Originally Posted by DirtyLarry

Really, do tell?

Originally Posted by DirtyLarry

The only caveat to this recipe is you must pay attention or you can overfill the tank pretty easily

You answered your own question...


Considering the return line issue... If it's possible to use the ECM to safely control the fuel transfer that's probably the way to go.

[DirtyLarry]

Originally Posted by hatzie

You answered your own question...


Considering the return line issue... If it's possible to use the ECM to safely control the fuel transfer that's probably the way to go.

The solution is simple....pay attention

[95 S_Trucker]

The GMT400 and 440 Trucks with dual tanks used a transfer pump from the factory.

The front tank was the main tank and the rear was the aux. There was a little module under the cab of the truck that would automatically fill the front tank.

My 96 had that system. It didn't work though, and the rear tank was in the way of the hydraulics for the rollback bed.

I removed the rear tank completely from the 96, and have it mounted on my 99 where the spare tire was. I have all the lines plumbed. I am going to add a switch on the dash to control a relay for the transfer pump, and I will have a small aftermarket fuel gauge on a pillar pod or under the dash. As long as you pay attention to the front tanks fuel level, you'll be fine.

I love my ccsb, but I don't love 10 mpg with a 26 gallon tank.

Its a similar system on a different truck.

If you are using an EVAP system, I would add a vent line between the 2 tanks. That won't be necessary if you are using vented gas caps.

[hatzie]

Originally Posted by DirtyLarry

The solution is simple....pay attention

Design considerations should include all the possible failure points and what the ramifications of that failure are.

Controlling the transfer pump with the ECM isn't simple or you would've done it rather than just turning the auxiliary pump on and off manually. If you do this it still places the fuel level sender in the critical safety path so it's not foolproof...

As I stated originally. Humans are easily distracted. Depending on human intervention to prevent a trail of gasoline on the road is asking for trouble. Diesel fuel is less flammable but no less problematic.

The safest way to use the system, as you have it setup, is to run the main tank below 1/8 before kicking on the transfer pump.

The WVO guys have come up with some pretty nice valves with 3/8" and even 1/2" fittings. They are not cheap but they will do the job safely. http://www.greasecar.com/article/gre...lve-comparison

I was never a fan of not having 2 fuel gauges. Putting 2 VDO 90Ω fuel gauges in one of Chris's pillar pods would allow you to monitor both tanks JIC the return valve stopped switching. You could have a clock and tach in the main cluster and maybe a transmission temp or some other gauge to round out the three pods.

[DirtyLarry]

Okay, whatever Hatzie

I think you are way over analyzing all of this where this would be an issue for a production vehicle with idiot drivers but for a project vehicle with one single driver your point is moot to me.

My system works great for what I use the truck for. I’ve learned to not even bother transferring fuel until the tank is practically empty or just wait until I am setting up camp at the end of the day (remember my truck is a purpose built off-road camping rig that doesn’t leave the garage unless it’s going somewhere exciting.). I would be lying if I said I never said I spilt any fuel by over filling as I have on our Death Valley trip a couple years ago until I got used to the speed of the transfer but the last several trips I didn’t spill a teaspoon of fuel. Sounds like a transfer system would not be safe for you to use though .....just razzing you

[hatzie]

I'm a darned engineer and I tend to be very conservative about equipment someone else could use and screw up.
Like my much better half.

[Chevy_mud_truck]

I have to though hard on this as well but I will be running diesel fuel with a fass fuel pump and that was the only thing I could think of was a transfer pump where the fass has 1/2 lines

[hatzie]

You can plumb the system with 1/2" pipe but the stock 1/4" fuel fitting in the head of the DB2 or DS4 will stay the same.
This guy has 3/8" DB2/DS4 fuel fittings but that's pretty much the limit.
http://walkingjdesigns.myshopify.com...feed-the-beast

The Greasecar valves are all available in 3/8" and since that's the limit at the Injection pump there's no reason to go bigger. The 6.x Detroit AMG engines are not built for performance. If you're wanting more sock in a GM chassis without moving to a Dmax you need to crossbreed with one of the 7.3L IH Navistar or 5.x Cummins engines.

[Chevy_mud_truck]

Forgot to add I will be installing a cummins
78 crew cab long bed dually 4x4 with 2000 24v cummins nv4500 205 transfer case Dana 60 front Dana 80 rear 4:10 gears all custom dash with all the wiring from 24v with a tuner bigger injectors hot rod vp pump fass lift pump and haven't made up my mind on a turbo setup yet

[hatzie]

Originally Posted by Chevy_mud_truck

Forgot to add I will be installing a cummins

The Bosch VE Injection pump on the 4BT & the 6BT uses a Banjo fitting on the fuel intake that's at least as restrictive as the 1/4" fitting on the Stanadyne DB2/DS4. I don't have as much experience with the P7100 Injection pump on the later Cummins Dodge but it uses a similar Banjo fitting so 3/8" is way more fuel line than you'll ever need.

[Chevy_mud_truck]

I understand what your saying I was just going by what in the kit it comes with 1/2 fuel line and all the fitting I'm running vp44 pump this is the fitting they send to go into the pump

[Chevy_mud_truck]

This kit is close to what I have

[496 BB]

Yea thanks Larry I figured youd chime in. I like the fuel pump idea better. I will be doing some time tests with it to see how long it takes to fill at 1/4 left and then set my delay switch up from that. I like keeping the crossover idea as well but doubt I go that route. Its just an around town truck and my snow plow rig. Its pulls dual duty but is no means a daily driver. Once I fill once on route I will stop and fill both up so no biggie. Dont need to see where the aux is after it transfers.

Still a ways out but hopefully soon. Finishing up my wiring harness little by little this past week. Still need to get a few more things wrapped up and then test fit it and order all split loom and all that jazz so....

[hatzie]

Your actual crossection on the JIC fittings is probably right around 3/8". You can more than get away with a pair of the Greasecar 3/8" SV-200 valves.

[Chevy_mud_truck]

One other thing is fass has a return line as well as the injection pump so I would valve with ports for inlet/outlet/and 2retuns plus stepping all of 1/2 lines up and down looks like to many place for a leak or more cost to buy more line and fitting I will be checking this post to see how every one is setting there's up (hint hint) pic would help to thanks for the help