Getting fuel from both tanks with one pump.

I am going to use one low pressure pump pull fuel to feed the swirl pot then use one high pressure to get the fuel to the engine...with two filters between these parts (one 75 micron and one 10).

My question is, just how should I go about linking the two tanks? Now, I don't have access to the inside of the tanks since they are assembled. Do I need to dismount one, cut it open on an end, add a fitting, have it welded back up, mount it back again, repeat on the other one, then hook a line between the fittings.

OR would a Y adapter pulling fuel from both tanks work do you think?

This would have the same issue as two low pressure pumps...one sucking air when the fuel got very low compared to the other, but it would allow for 90% of the fuel to be pulled out of both tanks I would think (foam filled tanks).
 
You could plumb eacn tank over to a selector valve and control which tank you use by a selector switch from the cockpit. Aftermarket stuff provides quite a choices. This, from Summit is an example.
http://www.summitracing.com/parts/smp-fv5k/overview/
I think that unit is set up for a return flow arrangement which you might need with fuel injection but it's just a sample to illustrate the options.
 
Hello
Before to decide to go on one pmup only you have to check flow capacity of your hight pressure pump ( corresponding of course of what needed in your injection system !!!)
Normaly these hight pressure pumps have much more flow than any low pump ( considering specilly the drop down due to hoses and fitting restrictions)so with full throttle you will have qite quickly your swirl pot empty because one low pump will not sufice to fill !! Big risk of damaging HP pump with cavitation issues

it's more than advisable to use 2 pumps ; then these 2 pumps can suck to reservoir or thru and 3way valve ( you will select which tank you want)

They must be protected by check valves in beetween swirl pot and outing due to some pressure coming when return flow from injection overflow that swirl pot

Hope this helps
 

Dimi Terleckyj

Lifetime Supporter
Hi Michel

To avoid this problem you connect the excess return line back to the swirl pot and the overflow from the swirl pot back to the tank.

This way the low pressure pump fills the swirl pot and the return line from the injector rails also fills the swirl pot and the total excess is then returned to the tank from the swirl pot keeping it full always.

Dimi
 

Ian Anderson

Lifetime Supporter
Ok
I have such a system on my car

Each tank through filter to pollack valve to swirl pot
Swirl pot to pollack and back to tank from which fuel was drawn

From swirl through Bosch 044 hp pump to fuel rail return to swirl

I am running a 'Morgan rover tuned unit at 256hp
Lp pump is a Facit red top hp is a Bosch 044
I have managed to outrun the lp pump on track as the engine coughs with intermittent fuel
I have burnt out one Bosch044 doing this over a four year period
I have also had one pollack valve fail on me ended up drawing from one tank and returning to the other causing overflow on that tank again about four years use
Second pollack is starting to go the same way


So I have now purchased a few electrically operated solenoid valves that I will connect up so

Energise via toggle switch one side of car to energise
Fuel sender to read to gauge
Fuel pump low pressure and two solenoid valves one on feed and one on return

Toggle in middle position all four solenoid valves in closed position

Toggle to other side for other gauge sender, pump and solenoids

Hp pump will run constantly on the ignition and cut out in two seconds from ecu once engine stops

Ian
 
Thanks for the feedback guys.

I like the idea of the ease of installing the selector, but I'm not sure how to go about sending two signals to a single fuel level indicator. Maybe install another one?

I've heard there are, issues, with Pollack valves to say the least so want to avoid that solution if possible.

I did stumble over something that would allow me to more easily do the simplest solution...connect the tanks themselves. There is a company that sells self sealing fuel tank taps (Methanol Injection : Alcohol Injection : Water Injection : DevilsOwn).

Only problem is it only supports a 1/4" line. I guess I could put two of these in and then link them together using a Y adapter to go to one 6AN line then another Y on the other tank splitting into to more of the self sealing taps.

Sound viable?
 
Darrin,
You don't have to make this that complicated. Dimi's arrangement is similar to mine. I have just one low pump and one high. You have several problems with the tanks we have .
FLAPPER VALVE
The first is to get the fuel to stay around the pickup. You do that by adding a flapper valve or sump arrangement around the pickup.
P8190255.jpg


When you go down hill or stop, the fuel will slosh forward and the pump will suck air. The LP is forgiving and it won't damage it unless it is constant. To augment that the return to the tank should be to this area as well. Thus making fuel available when those events occur.
BAFFLES
Baffles in the tank would help as well. Hope your tanks has them cause to add them is when the tanks are built. The flapper valve can be added by making an access cover above the pickup area. This cover can hold the fittings for the pickup , vent lines and fuel level gauge(cenntroid works best). The fuel level sender has to be outside of this arrangement. Otherwise it will show full tank all the time until all the fuel is gone!!
FUEL PICKUP
There is an argument as to where to have the pickup area. Some say at the rear of the tank. Some say in the middle. It doesn't matter as long as you lay out your lines and flapper valve arrangement correctly. The only difference is that if you put your pickup in the middle, you need two flappers, one on either side of the pickup to catch the sloshing to and fro. The vent lines still have to be at both ends of the tank(more about that later), and the return in the pickup area. .
FUEL LINES
First off the pickup needs to be a sock covered line to keep trash from getting into the line. This flows through a regular fuel filter to the LP pump. This then flows to the swirl pot which gravity flows to the HP pump. This line continues to a 75-100 micron filter on its way to the carb or FI. If carb you may or may not want a return line to the swirl pot. If FI you do. From the swirl pot the overflow line from the top should go to only the tank where the pickup is located, and placed inside the flapper valve arrangement. This keeps fuel at the pickup during stopping or going down a short hill. Some will say to have a pickup in the front and rear, but I don't plan to be climbing mountains with mine. and one or the other will be sucking air almost all the time. If you park on an incline you may experience some trouble getting cranked, but there should be fuel in the swirl pot.
Tank.jpg


This was one of the early drawings. It has the return to the tank with no pump. This arrangement will over fill that tank and it will cause fuel leaks at the most inopportune moments. If it were an air tight arrangement then it probably wouldn't
Your next problem will be getting fuel from the other tank.. The tank that has no pickup will have a cross over line to the one with the pickup. It doesn't have to be big. A 3/8 or so line is fine. As the fuel in the primary tank drops the other tank acts as a giant reserve tank. These takeoffs are at the bottom of the tanks somewhere near the middle. Keep it low and level, not over any upper frame rails. I have a ribbed bottom so the line fits easily in the ribs and is protected.
P1010056-1.jpg


If you are building a track car you may want a larger line. There should be a check valve in line here to keep fuel from sloshing back to that tank.. Routing this line will require some thought.
VENT LINES
You will need to run lines from the front and the rear. Here's why. With a full or nearly full tank there will be an air bubble at one end or the other. As the fuel temp rises from any heat source(sun or returning fuel) it will expand and if there isn't a vent it will buildup pressure. Opening a fuel cap would not be fun. There has to be one on both ends and they should be linked
P9060285.jpg


with a rollover valve in place beyond the link. I have one that requires about 2cm of H2O pressure to exceed on back flow, so that air can get into the tank as its level falls.
P9060282.jpg


I believe Demon Tweeks carries them. Where you put your exit is your option. I have mine at the fuel fill.
Sorry this was so long winded. Just a lot of material to caver. Hopes this covers your questions. PM me if this isn't clear.

Bill
 
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Thanks for the detailed message Bill.

My tanks are foam filled with a pick up at the rear that is accessed through the top but has an aluminum tube that extends to the bottom.

In theory, this foam should keep some fuel around in most instances.

From that I have a 75 micron filter that will be attached, and the other side of that is a low pressure (but high volume) pump. That feeds a swirl pot, then onto a high pressure pump and a 10 micron filter. The system has a return (EFI engine).

The only issue I see is getting the fuel from one tank to the other. I'm confident that the setup will keep the engine fueled without issue. It's just linking the tanks I am worried about. Talking to the maker of those fittings now and I think they may be able to make them larger or at least use 4AN fittings.
 
Quick update...

They don't offer 6AN or larger but they will make these up using 4AN fittings.

So, my plan is to use two of these to feed into a Y adapter that outputs a 6AN size. I will link a line up to that to go to the other side where I will have another Y adapter take the 6AN input and output two 4AN lines that will feed into the other two self sealing tank taps.

In my mind, this should work fine, but as I've never done it before...
 
Darrin, before you do - DONT, you really are going down a very wrong route with your thinking, and whilst there are a great many alternate suggestions to " how to do it" please either get a very clear and proven system or get a very good insurance policy, you will need one or the other ! Frank
 
The fuel valve from the twin tanked jaguar xj12/6 is a robust large bore valve , its also quite cheap at around £60 but more important is they are very reliable. the return valves are also good. This is what we have used on the first car we built and will be using them again.

Three port valve

No11737_CBC4269.JPG








Return stop valve below. X2
moHi-L_dCGUB2Afi2hupTAg.jpg


Bob
 
Darrin, before you do - DONT, you really are going down a very wrong route with your thinking, and whilst there are a great many alternate suggestions to " how to do it" please either get a very clear and proven system or get a very good insurance policy, you will need one or the other ! Frank

What exactly would you suggest then?

Right now, I'm leaning toward installing a connection line between the two tanks. Probably end up cutting the tanks and putting in something other than the self sealing thing though.

To me, this is the simplest, most straight forward and foolproof thing that can be done. In my experience, the simplest thing that can work is almost always the most robust. If you see a flaw with doing this though I'd really appreciate it if you would point it out specifically.

In short, what is wrong with connecting the two tanks with a fuel line in between? Is there something inherently unstable with this? I'm just not seeing it except perhaps that a valve to prevent reverse flow might be a good thing.
 

Dimi Terleckyj

Lifetime Supporter
Bill and anyone else with a DRB.

As per the photos there is a chassis rail that runs right across the car from one side to the other that lends itself to having a hole drilled into it to allow a direct connection from one fuel tank to the other for either fuel lines or wiring.

If the hole is drilled at the lowest point of the rail it comes out below the fuel tank and ensures that the fuel line or wiring is fully protected within the chassis.

In both my 40's I drilled a 25mm hole and installed a conduit to provide further protection from any sharp edges.

The photos show the chassis rail in Bill's car just to the left of where Bill ran his fuel line and in one of my cars with the conduit fitted.(photo of my car is upside down)

Dimi
 

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How do you fill up both tanks at the petrol station ,fill one
Tank then try and fill other tank but then the other tank
Has put fuel in the tank your now filling or may be take a
Long time with a slow fill. What about breather hoses would
you need four .When filling left tank breather hose from right tank
To left filler neck to enable filling from one side ?
 

Peter Delaney

GT40s Supporter
This is the way I did it - standard DRB setup with a change-over valve in front of a single LP lift pump, then to swirl pot, then to HP pump & rails. The change-over valve takes care of LP return feeds.

The change-over valve is an Ashdown 6 port fuel valve 27-90106 (Harness = 27-90107)

The LP pump is Ashdown Universal 12 Volt 30-48 KPA 27-FPE136

The HP Pump is Bosch : Petro Ject 10090 Fuel Pump External

Kind Regards,

Peter D.
 

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Thanks Peter. This makes sense to me and seems simple enough.

This is the way I did it - standard DRB setup with a change-over valve in front of a single LP lift pump, then to swirl pot, then to HP pump & rails. The change-over valve takes care of LP return feeds.

The change-over valve is an Ashdown 6 port fuel valve 27-90106 (Harness = 27-90107)

The LP pump is Ashdown Universal 12 Volt 30-48 KPA 27-FPE136

The HP Pump is Bosch : Petro Ject 10090 Fuel Pump External

Kind Regards,

Peter D.
 
Geoff,
I failed to mention the use of a one way valve in the crossover line. It only lets fuel flow to the tank with the pump. Most speed shops carry this.

Bill
 
I know JEGS has one BUT it requires 5psi to open up and a crossover line isn't really going to have any pressure behind it.


Geoff,
I failed to mention the use of a one way valve in the crossover line. It only lets fuel flow to the tank with the pump. Most speed shops carry this.

Bill
 
I know JEGS has one BUT it requires 5psi to open up and a crossover line isn't really going to have any pressure behind it.

Looks like Summit sells one that requires only 2PSI to open. I would think the weight of the fuel would account for that but I might check into it to be sure.
 
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