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Putting Espar fuel line through factory aux fuel port... essentially catheterizing the OEM system!

2486 Views 15 Replies 8 Participants Last post by  USA1169
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.
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Welcome to the forum and congratulations on your first posting.

I think you need a certain number of posts to be able to include photos. I could well be wrong. I hope that you can figure it out, photos would really help with this. I'm having a hard time visualizing your process. I haven't tried to do the install since I am still waiting for Espar to release the smaller B2L heater for the gasoline fuel.
 

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Discussion Starter · #4 ·
Welcome. Informative first post.

A little curious why you think this might be preferable to using the metal standpipe?
1) That float/pump unit is spring loaded between the lid and the bottom bucket so when you lock it down with the bayonet ring on top it presses the bottom bucket against the bottom of the tank and the entire assembly gets shorter. With the metal standpipe attached to the top you don't really know how far from the bottom the pickup ends up after the assembly is compressed like that.

2) There is a joint between the metal standpipe and the 4mm Espar supplied fuel line. That is an opportunity for a gap and a bubble to form (Espar says to take care not to have a gap at that joint for a reason).

3) The pickup at the bottom of the orange aux-port straw is fixed in a spot where it will not interfere with the float arm. Not sure there is any way to fix the end of the metal standpipe and still allow the assembly to compress. I just don't like the idea of that long skinny tube moving around down where the fuel level float arm is.

4) It's a lot cheaper than the metal standpipe.

5) One less hole in the top.
 

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Discussion Starter · #5 ·
Here is the assembly out of the tank. The drill bit is in the nipple at the top of the Aux fuel port before it was cut down. The pickup at the end of the orange fuel straw in my hand has been unclipped from the bucket at the base.

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Slice the top off the aux fuel port nipple to reduce the height and give you more room for the fuel pipe to turn 90. This also reduces the leverage the fuel pipe can exert on the molded plastic. After cutting off drill out to a #22 tap drill size by stepping up through a few different sizes. Ultimately this only increases the bore size by 0.5mm and there is plenty of meat left to support this nipple.
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The catheter ready to be installed inside the aux fuel straw. The Espar supplied 4mm OD and 2mm ID fuel line inside a length of 3/16" fuel line. An Espar supplied hose clamp is loose on the 3/16" hose.
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Use the same #22 drill bit to very slightly widen the bottom pickup straw to alow the 4mm fuel line to pas through from the shortened top nipple out the bottom of the straw. Blow any plastic cutting out with an air hose and clip the straw back over the edge of the bottom bucket to secure it to the side of the bucket where it was originally.
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Set the depth of your new fuel pickup. I stuck enough pipe out the bottom of the straw to put the pickup point 1.5" above the bottom of the tank. Not sure yet how much reserve this leaves me with but if I ever run it dry I will be sure to post the result.
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The completed "catheterized" assembly. The worm-gear style hose clamp that is just visible secures the 3/16" hose to the cut-down nipple on top. That is a tight enough friction fit that you probably don't need the clamp but it makes sense to put one on. The Espar style clamp a few inches down the hose seals the system from any vapor by-passing the space between the 4mm hose inside and the inside of the drilled out nipple (that is a snug fit using #22 drill bit). I left the 3/16" hose long enough to protect the 4mm line where it passes between the tank and the bottom of the van floor and framing. Reinstall and connect your fuel pump.
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Discussion Starter · #6 ·
One additional reason to do it this way instead of with a metal standpipe....

If you ever want to modify the height of the pickup point it would be easy to do without removing the entire unit. Just loosen the two hose clamps on the 3/16" fuel line and slide it back to expose the 4mm line inside. Put a reference bit of tape or a Sharpie mark on the fuel line and then either pull some out to increase your reserve level, or push it in to go deeper into the tank. Replace the 3/16" cover hose and clamps.
 

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Thanks for this write-up. Hopefully I will be visiting this soon.

When ordering my van I reached out to Jim Rixen to see if there was any value in ordering Ford’s Auxiliary Fuel Line Extension. His reply was this:

————
“We have a setup that runs a small nylon line through the aux fuel port at the top of the tank. It then attaches to our fuel line for the furnace. It does two things . It lets you set the depth in the tank and removes the problem with the large dip tube from the factory. It has a boot that slides over the fuel port and gets clamped.”
————

Sounds like a similar solution, but perhaps without any permanent modifications. I haven’t ordered the Rixens system yet but will pass along any useful info when I get it.
 

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thank you for the very detailed post!

However, I do question the physics you stated about the high altitude pressure reduction causing the system to lose prime.
At sea level, a pump can draw gasoline a maximum of approximately 15m upwards, and at 3000m altitude the pressure is reduced to about 70% of sea level. So a pump could only raise gasoline 10m up a tube at 3000m altitude. I think we have plenty of margin in our fuel pump's ability to draw gasoline up a tube that is only a few tenths of a meter up from the fuel level.
 

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thank you for the very detailed post!

However, I do question the physics you stated about the high altitude pressure reduction causing the system to lose prime.
At sea level, a pump can draw gasoline a maximum of approximately 15m upwards, and at 3000m altitude the pressure is reduced to about 70% of sea level. So a pump could only raise gasoline 10m up a tube at 3000m altitude. I think we have plenty of margin in our fuel pump's ability to draw gasoline up a tube that is only a few tenths of a meter up from the fuel level.
In theory, theory and practice are the same; in practice, they are not.

The standpipe has less issues at elevation according to those who have had issues then seen them resolved by going to the standpipe.

That said... this solution looks like it solves a problem that isn't a problem - the standpipe works great and I can hardly see the price of it being a factor relative to the heater itself. But... to each their own! (y)
 

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Nice detailed post, appreciate it!
 
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Discussion Starter · #11 ·
thank you for the very detailed post!

However, I do question the physics you stated about the high altitude pressure reduction causing the system to lose prime.
At sea level, a pump can draw gasoline a maximum of approximately 15m upwards, and at 3000m altitude the pressure is reduced to about 70% of sea level. So a pump could only raise gasoline 10m up a tube at 3000m altitude. I think we have plenty of margin in our fuel pump's ability to draw gasoline up a tube that is only a few tenths of a meter up from the fuel level.
You are correct.... if the end of the tube is in fluid and the system is static on a bench. This is anything but static, the fluid column is accelerated over bumps, the fluid in the tank is sloshing past the straw creating suction and exposing the end of the straw to air. All we really know is that a lot of people are reporting losing a pump prime with the aux fuel straw at altitude. At altitude there is lower air pressure on one side of the tube, that may be the tipping point... or maybe it is as simple as when you are at altitude you are likely driving on more slopes and that exposes the straw to air more often. The solution is a small enough tube that the fuel stays in it under those conditions. So a standpipe, Rixen's slimmer nylon tube mentioned above, or this approach.

For me, with the tank dropped on a weekend and no way to source a standpipe, or Rixen's slim tube, from the local auto parts store this was something I could do to keep the project moving and get the tank back in so I could drive my van on Monday. It gives me a continuous tube without joints between the fuel and the pump, and it allows me to set the level of the pickup. Done, on to the next event!
 

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This is anything but static, the fluid column is accelerated over bumps, the fluid in the tank is sloshing past the straw creating suction and exposing the end of the straw to air.
Thank you - this makes a ton of sense. A smaller diameter tube will also have more surface tension helping to keep fuel from sloshing out in these cases.
 

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You are correct.... if the end of the tube is in fluid and the system is static on a bench. This is anything but static, the fluid column is accelerated over bumps, the fluid in the tank is sloshing past the straw creating suction and exposing the end of the straw to air. All we really know is that a lot of people are reporting losing a pump prime with the aux fuel straw at altitude. At altitude there is lower air pressure on one side of the tube, that may be the tipping point... or maybe it is as simple as when you are at altitude you are likely driving on more slopes and that exposes the straw to air more often. The solution is a small enough tube that the fuel stays in it under those conditions. So a standpipe, Rixen's slimmer nylon tube mentioned above, or this approach.

For me, with the tank dropped on a weekend and no way to source a standpipe, or Rixen's slim tube, from the local auto parts store this was something I could do to keep the project moving and get the tank back in so I could drive my van on Monday. It gives me a continuous tube without joints between the fuel and the pump, and it allows me to set the level of the pickup. Done, on to the next event!
Haven't even gotten my transit yet but I did order the fuel filler extension and plan on doing some version of this hopefully without having to drop the tank. Do you think this is possible to do without dropping the tank?
 

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@USA1169 how has this install gone for you? Thinking I might try my install this way.

Curious if you've figured out how low of a tank you can still run the heater on
 

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I was thinking about modifying the factory dip tube as described but when I realized that would involve removing the tank (instead of just lowering one end) and removing and drilling out the float assembly, I decided to just hook up to the the factory fitting and see how that works. So far it is working fine with none of the glitches others have reported. My installation does help reduce fuel feed problems; having the Espar mounted under the floor on the driver's side with the pump below the centerline of the tank and the fuel line length only about 18".
I can tell you that the heater will suck air if the tank gets somewhere below 1/4 full. My next fill up was 22 gal on a 25 gal tank so I figure as long as you keep at least 5 gallons in the tank you would be fine. It took one extra cycle to get the system primed and working again.
 

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Discussion Starter · #16 ·
@USA1169 how has this install gone for you? Thinking I might try my install this way.

Curious if you've figured out how low of a tank you can still run the heater on
Three months on the road OR, CA, NV, AZ, ID and not a single issue. Espar fires immediately every time. Currently in the mountains of northern Idaho, often doing high altitude starts in sub-zero F conditions. So no air-lock issues yet. Fingers crossed!

I have not had the stones to get my fuel tank lower than 1/4 tank and still run the heater in these conditions. If I can remember I will try firing the Espar at a gas station before I fill an empty tank and see how low I can go and still get fuel.

This boiler is used to heat the floor as the first stage, and I have a fan coil for a second stage. There is nothing better than spending the day out in the snow and coming back to a van with a floor at 85F and 65F air temp. Bare feet on a warm floor, all the snow melt off boots and equipment evaporates in minutes, boots dry out easily, so do socks and gloves if you put them on the floor. A heated floor in a winter van is the bomb!
 
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