For Delica L300 with 4D56 & Automatic Trans
This installation will show how to add an auxiliary fuel tank in the former spare tire location. We used a universal 17 gallon fuel cell measuring 17″ X 30″ X 7″ (L X W X H). There are different sizes and shapes available off the shelf. There are also custom tank builders that will build a tank to your specs. But for $150 and an almost perfect fit it was a no-brainer. The entire cost of the installation was around $400.
There are a lot of small tweaks that need to be made to get it all to work. It is by no means turn-key installation, but it is functional and cost effective, with other solutions starting at more than double the cost. Everything is gravity fed and no cross-over fuel pumps are required.
This install will require a side-exit exhaust and re-located spare tire.
The fuel cell is fed through the stock filler, along with the stock tanks. The fuel cell feeds the stock tanks, therefor the fuel gauge will read full until the 17 gallons in the fuel cell is depleted. At that point the fuel gauge will read normally, as the stock tanks are no longer being fed from the fuel cell. Our fuel cell also came with a 0-90 Ohm fuel level sender installed. We bought a universal fuel gauge to monitor the level in our fuel cell.
Total fuel Capacity: 32 gallons
Total Highway Range: ~750 miles
Added Fuel Weight: ~120 lbs @ 7 lbs per gallon
Fuel System Diagram:
- The fuel cell is filled via a 1.75″ fuel filler hose tee’d off of the OEM 1.75″crossover hose. The fuel cell will start to fill once the OEM tanks are full.
- The fuel cell fill hose is run into the top of the fuel cell in order to provide suspension travel clearance over the rear axle/diff. See “Lessons Learned” for an update to this.
- The rear tank breather exits into the forward tank, then the forward tank breather exits into the filler neck. This daisy chain slows the exist of air from the tanks, leading to slow filling when topping off. I would like to add a switched solenoid valve breather to alleviate this issue in the future, discussed later on.
- The fuel cell outlet hose feeds the OEM tanks via the crossover hose (gravity fed).
- The siphon between the forward and rear tank ensures that the fuel level in both tanks is the same. Each tank has it’s own fuel level sender. The values are summed and sent to the dash. If the siphon ever sucks in air and “breaks the siphon”, then a float mechanism in the rear tank ensures that the siphon is restored.
- Fuel cell will need it’s own separate gauge if you want to know how exactly how much fuel you have. Otherwise you just deplete the fuel cell and then the needle will drop with the remaining ~15 gallon stock tank capacity.
Parts List:
- Fuel Cell This tank fits perfectly under with just enough clearance for the shocks and sway bar.
- 1-3/4″ House Coupler
- 1-3/4″ SS Tee
- 1-3/4″ Fuel Filler Hose
- 2X 8AN Weld-on Bungs
- M8X1.25-25 bolt
- M8 Copper Sealing Washers
- 1/4″ ID NBR fuel line
- 1/2″ braided NBR fuel hose
- 1/4″ to 1/2″ Hose Coupler
- 16mm X 12mm X 16mm Hose Tee
- 2X 8AN to 1/2″ Hose Elbow
- 3X 8AN caps
- 1/8″ Angle Steel 1″X1″
- 3/8″ threaded rod, nuts and washers
- 1/4″ Thick rubber Sheet/mat
- Hose Clamps for Tank Fill and Drain
- 52mm Fuel Gauge and wiring
Preparing The Fuel Cell
1. Cap the three 8AN fittings on the top of the tank. Shown below in red.
2. Check all of the nylon sealing washers on the fill cap flange. Some of mine were cracked. I replaced them and made sure everything was snug. Shown below in blue.
3. Inverting the level sensor. The level sensor in these tanks send out readings that are opposite from every aftermarket fuel gauge on the market (full=empty)…. stupid and annoying. I flipped and tack-welded the sensor on the opposite side of the pivot to correct this (using a piece of coat hanger) and send out usable resistance readings. I had to remove the filler flange to get access inside the tank to remove the sender assembly.
4. Weld on the tank drain 8AN bung- left side with 90 fitting.
6. Weld on tank breather 8AN bung located on the upper front vertical face of the tank-see below in blue. Weld on the 1.75″ hose coupler for the fill. Avoid going directly over the diff to increase clearance. Filler shown in red, breather shown in blue.
Lesson Learned: I have my tank-fill mounted at the top of the tank, as opposed to how the diagram below shows it, more in the middle. I did mine that way for clearance, but it results in a super slow fill since the the front tanks basically have to be full and the pump will shut off because of the high fuel level resulting in fuel in the filler neck. Filling takes a long time since I have to wait for the fuel to move top the fuel cell due to the high point of entry. So, a lower filler is better. Locate the filler so the bump stops will prevent it from being hit when the suspension is being compressed.
Fuel System Integration
1. Connect to the fuel filler cross-over hose between the two tanks. I used a 1-3/4″ SS tee to make the connection. The actual size is more like 1-5/8, but you cant find that size line or tee anywhere. I cut the cross over-hose and used a heat gun to stretch the hoses. My original hoses ended up being a bit dry rot and leaky so I replaced them with some off the shelf fuel hoses (Spectra FNH169 works well).
2. I used 2x of this Dayco hose It was partially discontinued at Advance Auto Parts so I got each for $1! I used a steel 90 elbow tube and welded mounts on it with angle steel. The 90 mounts to the frame using existing hardware from the exhaust heat shield and sends the fuel from the tee back to the tank. I used 1-3/4 EMT hangers and some custom bracketing to secure the hoses.
3. To set up the feed line I simply banjo bolted into the drain plug of the stock rear tank. I was originally going to weld a bung into the side of the tank, but that has its own challenges. Unfortunately all the M8 Banjo bolt kits I found were fine thread metric. The tank drain thread is standard pitch. So I bought a stainless steel standard pitch m8 bolt and made my own banjo bolt and bought some copper washers. I just put the bolt in a vice and drilled it appropriately. The longer 25mm length also keeps the fuel supply above the floor of the tank, avoiding debris. I stacked some extra washers on the tank side to get clearance for the hose and clamp. I recommend making a beefy skid plate to protect the bolt, I have yet to do that.
4. Run the line to the Aux Tank. This line goes up and over the axle and to the fuel cell. I converted to SS braided line part of the way through and connected it to my 90 degree 8AN elbow.
5. Next is the tank breather. This is a pain. The tube must be level or contentiously slanting upwards towards the filler neck (basically impossible to do unless you want to drill through every horizontal frame member). Any low spots trap fuel (P-trap) and then you have no more breather. I ended up tee-ing into the original breather between the two tanks ( located above the transfer case). It works but it is slow, since the original two tanks are daisy chained in terms of their breather system, so its a long run of 1/2″ ID hose, it does not keep up well with the speed of modern diesel pumps.
My future plan is to use one of the original fuel cell fittings on top and add a solenoid valve breather. So that way I can open an extra breather when filling up, and closed when driving. The solenoid valve would be switched to the fuel door.
Fuel Gauge
1. I used a universal 52mm 0-90 ohm fuel gauge with tune-able sweep. I have this on a switch to constant 12V so that I can see the tank level when at the pump. I don’t always have it on while driving, just flip the switch to quickly check the level.
Tank Mounting
1. The tank is just mounted with 4 pieces of all-thread and angle steel to the floor with some fender washers. There is a 1/4″ sheet of rubber between the tank and frame member. This is for good measure and gives a little more clearance for the sway bar. The tank is mounted off-center to accommodate the fill line next to the shock absorber.
Diesel Heater Connection
We later fitted a diesel heater by simply teeing off of the fuel supply line. This was done at a point above the floor of the stock tanks, ensuring that the diesel heater cannot run the tanks dry and leave us stranded. A manual shut-off and check valves were installed to isolate the heater and ensure the heater does not loose its prime. Aluminum bar stock added to existing bolts was used for bracketing.
Additional Breather Installation
As previously mentioned, the original breather system is slow, especially with the addition of this extra tank. To alleviate this issue, a second breather has been added directly to the fuel cell. To make sure this breather does not leak or introduce contaminates into the tank, the breather is controlled by a valve.
A 12 VDC solenoid valve opens the breather only when the fuel door is open. This valve is wired with a switched ground to reduce the number of wires that need to be run.
The breather and valve are plumbed off of the original tank fuel return fitting.
