It is possible to thread the Espar supplied clear 4mm OD fuel line through the factory auxiliary fuel port on the float/pump unit. This eliminates the loss of prime and need to cycle multiple times to get fuel back into the rather fat straw running from the aux port connection down to the bottom of the tank. It also allows you to set the height of the pickup in the tank where you want it.
The steps are:
1. Pull the float/pump unit from the tank.
2. Remove the cap on the aux port and cut the nipple off just below the shoulder that the cap locks onto. The best way to do this is with a sharp draw knife, making multiple pulls across the plastic stem to slowly cut through it cleanly.
3. Drill out the port nipple using increasingly larger bits until you get to the proper size. There is plenty of meat in the plastic molding to do this. You are only increasing the diameter by 0.5mm. A number 22 drill bit from a thread tapping index is the final size you need.
4. You also need to slightly enlarge the half moon profile straw at the bottom of the orange straw. The best way to do this is to carefully remove the white plastic end by unclipping the three tabs holding the entire float/pump unit into the bottom bucket. Lift the guts about half an inch up out of the bottom bucket and that straw end will come free. Then drill it out.
5. Get a few feet of 3/16" fuel line and run the clear 4mm OD Espar supplied fuel line inside of it. You are going to use this outer fuel line to seal the nipple that you cut down on top to the 4mm fuel line. Slide two hose clamps over the 3/16" line. The 3/16 fuel line will also act as a bend support for the initial 90 and chafing protection as the line runs out from on top of the tank. You can use the Espar supplied clamps to squeeze the 3/16" line tight to the 4mm Espar line inside, but those clamps are not big enough to go over the nipple that you drilled out.... so get a slightly bigger clamp for that.
6. Slide the 4mm Espar fuel line through the nipple you cut off and drilled out, down through the ribbed orange straw, and out the white half moon profile pickup at the bottom that you also drilled out. Clip the bottom pickup back onto the side of the bottom bucket. Adjust the amount of 4mm Espar line that sticks out the bottom to whatever height you desire the pickup. This determines how much fuel is left if your Espar heater is allowed to run until it sucks air. Some say leave 1" but I left 1.5" just to give me a bit more of a safety margin to exit back-country winter situations. Setting it at 1.5" puts the pickup an inch lower than the top of the opening on the OEM straw.
7. Slide the 3/16" fuel hose over the nipple you cut down and clamp it on. Make sure that does not push the 4mm fuel line to a different elevation. Then slide the Espar provided hose clamp a few inches away and clamp it tight to make the system vapor tight. I moved it far enough away from the nipple so that it was past the 90 bend the line makes after exiting the tank.
8. Put the float/pump unit back in the tank and replace the tank.
You now have a fuel pickup with a 2mm ID running without interruption to the pump. All of your issues with losing prime go away.
For what it is worth the problems people are having with air in the fuel at high altitude have nothing to do with vapor pressure. I have done a lot of work on aircraft fuel systems and I can assure you that you are never going to drive your van anywhere near an altitude where this becomes and issue. It is more likely that the larger diameter orange OEM straw simply cannot hold a column of fuel in it at higher altitudes. That column of fuel is like a piston in a cylinder with the weight of the fuel trying to pull a vacuum at the top... but we forget that at the bottom atmospheric pressure is pushing the piston up. As you gain altitude the push from the bottom decreases. As that happens at some point the column of fuel in the straw just cannot hold itself up and it breaks down and flows out.
If someone can tell me how to post photos I will happily add them.
