Install a diesel air heater

Motorradmark

Well-known member
I finally got a planar diesel air heater to warm up the drafty cab.

Any advice on where to tap for fuel. Was thinking about putting a T fitting in the return line, but wanted to check before cutting anything.

Thanks
300 tdi if it?s important.
 

Napalm00

Well-known member
I finally got a planar diesel air heater to warm up the drafty cab.

Any advice on where to tap for fuel. Was thinking about putting a T fitting in the return line, but wanted to check before cutting anything.

Thanks
300 tdi if it?s important.
T fitting in the return line will just pull air from the tank when the truck is not running, or possible when it is running. this is due to that the return line is not below the fuel level in the tank on some trucks.

You can "T" the feed line from the tank, BEFORE the lift pump as the planar heater has its own fuel pump. depending on how your system is plumbed you can also get fuel from after the filter but before the lift pump if you want to supply filtered fuel.
 

Motorradmark

Well-known member
Makes sense, thanks.

My fuel system goes. Tank, Richard?s sedimentor, electric fuel pump. Fuel filter lift pump.
Would think bwtn sedimentor and elect pump would be ok. Yes?
 

Red90

Well-known member
The only really reliable way is a dip tube in the tank. Tying into fuel lines always leads to reliability issues as any tiny air bubbles that come along cause the heaters to flame out.
 

RDavisinVA

Well-known member
You absolutely need a separate fuel pickup in the tank or a separate fuel tank with it's own pickup.
We are going to use a 3 gal vented reserve tank.
The reserve feed will T-off the main fuel line just after the 12V fuel pump which is just in front of the sedimenter.
The flow through the T is via a 12V solenoid.
When the key is on that activates the 12V fuel pump and you switch the 12V solenoid open, the 12V fuel pump will fill up the 3 gallon tank off the main diesel tank.
Then you'll close the 12V solenoid and run the auxiliary heater off the fuel in the reserve tank.
There will be a second 12V solenoid T-off the feed line at the sedimenter.
When this is switched on, the engine can run off the reserve tank.
If you run the engine off the reserve tank, you can't run the auxiliary heater.

This may sound like overkill, but after running out of fuel several times when the fuel gauge suddenly started reading high, will have the piece of mind of being able to use the auxiliary tank when the main tank is emptied.
 

Motorradmark

Well-known member
What did you use for the 3gal reserve tank and do you have the info for a 12v solenoid t fitting? Sounds very reliable and certainly provides some backup as well.

Thanks Richard
 

RDavisinVA

Well-known member
This would work:
https://www.summitracing.com/parts/tnk-sov?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-tanks-inc&gclid=EAIaIQobChMIxu2D0Oe72AIVDnh-Ch2AqgjLEAQYASABEgJG9PD_BwE

When the valve is closed (not energized), the fuel goes to the engine from the main tank.
Open the first valve and fill up the auxiliary reserve tank via the 12V fuel pump.
Close the first valve and start the engine and run off the main tank.
Open the second valve and you are running off the auxiliary reserve tank.
Close the second valve and you are running off the main tank.
If you get 20 MPG, you have plenty of fuel in the auxiliary reserve tank to drive somewhere and fill up the main tank if you ever run the main tank out of fuel.
Running out of fuel is a pain in the ass.
Naturally when you are not running off the reserve tank, you have lots of fuel for the diesel air heater.
You could actually run the diesel air heater and engine off the auxiliary reserve tank at the same time if you wanted.
The only thing I didn't mention was you could T lines to filter the fuel before it gets to the auxiliary reserve tank, but you can control this by where you install the 3 way valves.

This is the set-up for the 110 Diesel Dormobile.
 

Napalm00

Well-known member
You know I don't have one why exactly do you need this second tank? Just so you don't run yourself out of fuel in the main tank by accident?
 

RDavisinVA

Well-known member
You know I don't have one why exactly do you need this second tank? Just so you don't run yourself out of fuel in the main tank by accident?
All the manufactures recommend a separate tank or a separate fuel pickup.
Since there is no provision in the main tank for a separate fuel pickup for the diesel to air heater, so you need to modify the main tank or you need a completely separate tank.
T-ing the main fuel line will not always work well.
Most heaters come with a fairly thin small plastic tank that is a pain in the ass to fill up.
I don't like the idea of the small plastic tanks that can be messy to fill up.
So the above posts describe my solution.
 

Napalm00

Well-known member
I guess I understand that it just seems like a ton of work. I mean the diesel tanks on 200-300 in earlier trucks couldn't be simpler, and since there's no pressure whatsoever before the lift pump I don't see how it couldn't work unless the installer fat fingered something

I really like the idea of a separate tank it just seems really complicated
 

RDavisinVA

Well-known member
I really like the idea of a separate tank it just seems really complicated
Almost every foreign concept seems really complicated during an initial exposure.
It's really pretty simple.

I recall the first time being exposed to a 12V relay, it seemed very very complicated, although in reality very simple.
 

Z.G

Well-known member
The only really reliable way is a dip tube in the tank. Tying into fuel lines always leads to reliability issues as any tiny air bubbles that come along cause the heaters to flame out.
What would your suggestion be to a plastic tank vehicle?
 

Red90

Well-known member
It is pretty easy to add a second dip leg to the main tank. Pull the dip leg and add in a 1/4? steel tube. There is a lot of room.
 

Motorradmark

Well-known member
My metal tank has a dip tank on the that is not being used. Main fuel line goes via the output in the sender unit and the return goes back in on the other side. Going to try that out.
 

Napalm00

Well-known member
My metal tank has a dip tank on the that is not being used. Main fuel line goes via the output in the sender unit and the return goes back in on the other side. Going to try that out.
If you connect to the top of the tank on the side near the filler it will only pull air. That port doesn't go down into the fuel.

Pic attached is the inside of a 200/300 tank setup for diesel.
 

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