Low fuel level starvation issues

Hasenwerk · Aug 16, 2018

My ALH Ranger has a +-55L fuel tank. It's quite long and narrow. When the fuel level gets to about 20L remaining, I start to get air bubbles in the fuel line especially in town, with stop and go traffic and you can feel the engine mildly cut out from this.

I know running a fuel pump in the tank helps with this issue, but after having three gasoline fuel pumps pack it in over the last two years, I have been going without. I am still using the "sock" at the bottom of the assembly and the spring is in there ensuring it is sucking from the bottom of the tank. I just replaced the fuel pump with hose.

I was thinking that I should tee the return fuel line back into the intake fuel line so that no fuel gets returned to the tank. Good idea or no?

Vince Waldon · Aug 16, 2018

QuickTD said:
Bad idea to recycle the return fuel. The only way air gets out then is through the injectors.

Also very important to return the (hot) return fuel back to the tank so it can get diluted and cool off.

My MK4 Wagen actually has a small heat exchanger on the return line under the passenger side... and it gets pretty warm.

1.9ZOOK · Aug 18, 2018

I'm also running an inline Facet brand,4-6 psi. It has held up for two years now with no problems.

AndyBees · Aug 20, 2018

I've experienced very similar issues with the aftermarket fuel tank in my Vanagon (ALH engine). The tank holds 16 gallons (60.5 liters). When the fuel level gets down to about 3 gallons (11 liters) as I go thru curves in the road at a fairly high speed, especially going up hill, air bubbles get picked up. The engine has actually quit running on two occasions and acted up several times due to low fuel with air bubbles. So, I try to never let it get down below 5 gallons.

Anyway, my experience with opening up the bottom of an OE Vanagon fuel tank is that the return fuel is dumped within very close proximity of the pick-up tube (bottom center of tank). I have no idea what the new aftermarket tank return fuel pipe and pick up pipe relationship might be.

So, to alleviate the problem I installed a Facet style pump in-line using a check valve parallel to the pump. Normally, fuel is "pulled" through the check valve and the pump simultaneously. But, when I flip on the pump, it pushes fuel against the check valve via a T in the line and at the same time it pushes fuel on to the filter at the engine. I set it up this way so that fuel pulled through the Facet style pump wouldn't add suction resistance to the IP. Also, I do not have to constantly run the pump.

I was not aware of a system to eliminate air bubbles as used in the big rigs. Sounds as if that would be something that could be very beneficial to my fueling set-up.

ToddA1 · Aug 20, 2018

Vince Waldon said:
My MK4 Wagen actually has a small heat exchanger on the return line under the passenger side... and it gets pretty warm.

Is that a factory part?

-Todd

AndyBees · Aug 20, 2018

ToddA1, I believe the heat exchanger is only on those cars with the Automatic transmission. I've never seen it on a car with the 5-speed manual tranny.

It is located under the car just about under the passenger front seat.

catbed · Aug 20, 2018

Hasenwerk said:
My ALH Ranger has a +-55L fuel tank. It's quite long and narrow. When the fuel level gets to about 20L remaining, I start to get air bubbles in the fuel line especially in town, with stop and go traffic and you can feel the engine mildly cut out from this.
I know running a fuel pump in the tank helps with this issue, but after having three gasoline fuel pumps pack it in over the last two years, I have been going without. I am still using the "sock" at the bottom of the assembly and the spring is in there ensuring it is sucking from the bottom of the tank. I just replaced the fuel pump with hose.
I was thinking that I should tee the return fuel line back into the intake fuel line so that no fuel gets returned to the tank. Good idea or no?

Have you looked into a Holley Hydramat type product at all?

AndyBees said:
I've experienced very similar issues with the aftermarket fuel tank in my Vanagon (ALH engine). The tank holds 16 gallons (60.5 liters). When the fuel level gets down to about 3 gallons (11 liters) as I go thru curves in the road at a fairly high speed, especially going up hill, air bubbles get picked up. The engine has actually quit running on two occasions and acted up several times due to low fuel with air bubbles. So, I try to never let it get down below 5 gallons.

Anyway, my experience with opening up the bottom of an OE Vanagon fuel tank is that the return fuel is dumped within very close proximity of the pick-up tube (bottom center of tank). I have no idea what the new aftermarket tank return fuel pipe and pick up pipe relationship might be.

So, to alleviate the problem I installed a Facet style pump in-line using a check valve parallel to the pump. Normally, fuel is "pulled" through the check valve and the pump simultaneously. But, when I flip on the pump, it pushes fuel against the check valve via a T in the line and at the same time it pushes fuel on to the filter at the engine. I set it up this way so that fuel pulled through the Facet style pump wouldn't add suction resistance to the IP. Also, I do not have to constantly run the pump.

I was not aware of a system to eliminate air bubbles as used in the big rigs. Sounds as if that would be something that could be very beneficial to my fueling set-up.

Very similar to a "surge tank" set up on a gasser, or a "swirl pot" in a coolant system. helps to have the fuel inlet from the main tank enter on a tangent to swirl the fuel and force the air bubbles to the outside. (round container of course)

AndyBees said:
ToddA1, I believe the heat exchanger is only on those cars with the Automatic transmission. I've never seen it on a car with the 5-speed manual tranny.

It is located under the car just about under the passenger front seat.

Yes, autos got them only. I would assume due to the 11mm injection pump.

Alchemist · Aug 20, 2018

PDs also got a return fuel cooler.

Millennium Falcon · Aug 20, 2018

My jeep shut off going down the road the other day.... I have a feeling it was the same problem you are describing.. Fuel was down to about 1/4 tank. I had to let it sit.... I cracked the injector lines and air bubbles came out without even cranking the engine over. I cranked until pure fuel was coming out... tightened them up, topped off the tank and boom started right up and has been running fine since. Its frustrating because im not 100% sure that air from low fuel level was the problem. I haven't been able to recreate the problem. I believe I will be installing an inline pump to help prevent this. If nothing else it will help me cross that off the list of possible causes.

Hasenwerk said:
My ALH Ranger has a +-55L fuel tank. It's quite long and narrow. When the fuel level gets to about 20L remaining, I start to get air bubbles in the fuel line especially in town, with stop and go traffic and you can feel the engine mildly cut out from this.
I know running a fuel pump in the tank helps with this issue, but after having three gasoline fuel pumps pack it in over the last two years, I have been going without. I am still using the "sock" at the bottom of the assembly and the spring is in there ensuring it is sucking from the bottom of the tank. I just replaced the fuel pump with hose.
I was thinking that I should tee the return fuel line back into the intake fuel line so that no fuel gets returned to the tank. Good idea or no?

Hasenwerk · Aug 20, 2018

I do have one of those inline fuel pumps and will be installing it here soon.

I think inside of the tank I am going to make a modification to the fuel pickup. As CATBED said, the hydramat idea is already in place with the factory pump housing (less pump) - there's a big sock at the bottom of the pickup that soaks up fuel, however, it's not a really good design. This is what I am thinking: Get a can and have it so it sits at the very bottom of the fuel tank in that depression. Inside the can is the fuel suction line and the return line and a sponge of sorts. The bottom of the can would have a couple of small holes that will allow the fuel to enter. The returning line empties into the can, this and the sponge will keeping it "full" and the suction line should have more periods where fuel will be available as it can't slide away during <25% full situations.

1.9ZOOK · Aug 20, 2018

I know it is not an easy solution but I also did this for super off camber wheeling
not knowing that I was eliminating all air bubbles at the same time.

That's the bottom of the tank.5/8 " hole feeds the after tank.

catbed · Aug 21, 2018

Hasenwerk said:
I do have one of those inline fuel pumps and will be installing it here soon.

I think inside of the tank I am going to make a modification to the fuel pickup. As CATBED said, the hydramat idea is already in place with the factory pump housing (less pump) - there's a big sock at the bottom of the pickup that soaks up fuel, however, it's not a really good design. This is what I am thinking: Get a can and have it so it sits at the very bottom of the fuel tank in that depression. Inside the can is the fuel suction line and the return line and a sponge of sorts. The bottom of the can would have a couple of small holes that will allow the fuel to enter. The returning line empties into the can, this and the sponge will keeping it "full" and the suction line should have more periods where fuel will be available as it can't slide away during <25% full situations.

I would think that the hydramat "holds on" to the fuel a little bit better than the factory sock, and it covers a larger area on the bottom of the tank.

The can set-up you describe is very similar to what is in my A8. The fuel pump sits in a little cup, maybe .5-1qt volume, with the return line feeding the can. There are a couple suction lines with a venturi on the return to pull fuel from the tank around the can. I think its a brilliant set up as the fuel pump is ALWAYS submerged in fuel down to the last drop(virtually), no matter the G-forces or inclination.

Low fuel level starvation issues

Hasenwerk

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Vince Waldon

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1.9ZOOK

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AndyBees

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ToddA1

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AndyBees

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catbed

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Alchemist

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Millennium Falcon

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Hasenwerk

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1.9ZOOK

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catbed

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