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Diesel fuel tap ideas ?

H

HarryN

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I am thinking about buying one of these portable diesel heaters - not necessarily this brand or model - but the concept is the same.

The main limitation of all of them is the 1 - 2 gallon fuel capacity. That is only 1 - 2 days worth.

My truck bed will be pretty full of stuff, so I prefer to not carry spare fuel tanks if possible.

What would be handy is if there is a way to pull some fuel from the main tank if needed.

My understanding is that on diesel engines, the lower pressure pump in the fuel tank pumps the fuel forward, through the filters, and returns any that is not going into the high pressure pump back to the fuel tank.

I am toying with the idea of tapping into this return line to pull fuel for the heater.

Anyone done something like this?

_____________

There are people that install a permanent model as well and pull from the main fuel tank - at least on vans, so I assume trucks as well. At the moment looking at the portable units.

Thanks

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wrvond said:
On the frame mounted filter there is a drain valve, why not just use that?
Click to expand...

Thanks - I am "hoping" to buy a 2025 +. They moved that fuel filter up behind the brake fluid reservoir if it is the same one we are thinking of. I will look for a tap there.

I might be confused though - will look some more.
 
The drain in the filter is where any water will accumulate, not sure I’d use that.

The return is post high pressure pump, the fuel from the lift pump goes thru the filter and then the CP3/CP8, into the rail and injectors, and then what isn’t used goes back to the tank. There is a return on the pump as well, for what it doesn’t use.

Your diesel heater would have to pull thru the lift pump to work with the engine off, which is how the pump is designed… in theory.

I’m not sure if there is a check valve in the tank on the return line or not, but if there is you won’t be able to pull fuel that way.

While it may not be the easiest install, a separate pickup in the tank would guarantee the best pump operation without messing with the engines fuel loop.
 
AH64ID said:
The drain in the filter is where any water will accumulate, not sure I’d use that.

The return is post high pressure pump, the fuel from the lift pump goes thru the filter and then the CP3/CP8, into the rail and injectors, and then what isn’t used goes back to the tank. There is a return on the pump as well, for what it doesn’t use.

Your diesel heater would have to pull thru the lift pump to work with the engine off, which is how the pump is designed… in theory.

I’m not sure if there is a check valve in the tank on the return line or not, but if there is you won’t be able to pull fuel that way.

While it may not be the easiest install, a separate pickup in the tank would guarantee the best pump operation without messing with the engines fuel loop.
Click to expand...

Thanks for the explanation.

Is there a back pressure regulator on the fuel rail that maintains pressure there, and then releases some / excess to the return line to the tank ?

__________________

Another possibility is to tap into the low pressure line after the lift pump closer to the bed area of the truck.
 
There is a HPRV for the rail return, the injectors have their own return, and a return off the CP3/CP8. All at low pressure.
 
AH64ID said:
While it may not be the easiest install, a separate pickup in the tank would guarantee the best pump operation without messing with the engines fuel loop.
Click to expand...

This is how the typical gasoline powered van is done. On the Ford version they drop the tank. On the RAM Promaster there is a second pick up line in the tank already so you just have to get to the top of of the fuel tank - which is not too difficult actually. I am not sure about on the MB sprinter.

The other methods are to use two different fuels - gasoline for the engine. ( propane or diesel for the heater )

The fuel heater has it's own small pump that pulls fuel "up" from the main tank and feeds the heater. The installations are fairly sensitive to installation details, need very specific loops, distances, location, etc. It also makes it so the heater can only be used just for the van and not in a trailer or garage, etc.

It is not a lot, but there is some annual maintenance involved to clean out soot, so access is required. I use a cane sometimes so that is less convenient.

If I can avoid the direct tank install - I will, but I get it that it is a risk.
 
Sprinters come with an aux fuel tap already installed in the tank, which is what I’ll be using for the DCH.
 
AH64ID said:
the fuel from the lift pump goes thru the filter and then the CP3/CP8, into the rail and injectors, and then what isn’t used goes back to the tank. There is a return on the pump as well, for what it doesn’t use.
Click to expand...

I also wondered about tapping into the line after the lift pump / before the filters. Was not sure how high this pressure is and hesitated to mess with the input side of the system.

The advantage of using it is that in theory the fuel priming arrangement could be used to pump fuel to the heater.
 
AH64ID said:
Sprinters come with an aux fuel tap already installed in the tank, which is what I’ll be using for the DCH.
Click to expand...

Do you think something like this exists in the RAM pickup trucks ?

@AH64ID Really appreciate the insights.
 
Not that I am aware of. You’ll have to add your own pickup tube.
 
Cut a sump into the bottom for your aux feed. Or put it in the side of the tank so you always have reserve.
 
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johnmyster said:
Cut a sump into the bottom for your aux feed. Or put it in the side of the tank so you always have reserve.
Click to expand...

Thank you for the suggestion and for all of the info in your signature. I am attempting to head down a similar starting point truck path.
 
I would not use a sump tap for multiple reasons, primarily the ability to run the tank dry with a heater and the low hanging snag point.

A simple draw straw that sits 5” off the bottom of the tank would be a much better solution.
 
Thanks for the ongoing suggestions.

This is nominally what the diesel heaters look like. A 1 - 2 gallon tank on the side of the mini suitcase with the heater in it.

The fresh cold air comes in the lower port on the yellow case and warm air is blown out through the top port. A hose connects this to the truck or trailer that is being heated.

This provides fairly decent fresh, dry, warm air to dry out wet clothes, etc.

The air inside the truck or trailer leaks out through either an accidental or on purpose air leak vent.

Harry
 

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