Fuel System Modifications

Being still abroad for work, I worked a little bit on my new fuel system diagram. As explained in this post, I had two different issues with the previous design that made me make some changes. I will explain a little more the reasoning behind each fix.

Fix #1: To solve the fuel siphoning problem

The fix for this problem is to install a vent interconnect between the two tanks. This way, if siphoning happens following an overfill, it will only siphon until the fuel level reaches the level of the vent port on the main tank i.e. minimum fuel loss.

A downside of this is that it allows the fuel in the header tank to flow back into the main tank while inverted. To prevent this, I will add a check valve on the vent interconnect line. It is important that the check valve be vented so that air can flow in both directions. Here is a picture to better visualize the change:

 

Fix #2: To solve the potential fuel starvation issue

This problem is more important, but the fix is simpler. Instead of feeding the pump inlet directly when using the aux tank,  I will connect the aux tank to the main tank, therefore eliminating the risk of feeding air from the aux tank to the engine:

I also made a small change to the fuel level indicator: the bottom end will now be connected to the header tank purge line. This will allow me to read fuel level down to the header tank level.

Modified top level diagram

The above is how I intend to connect the lines during the rebuild. I keep an upgrade for next winter: route the EDP vent line through the firewall so that its outlet gets further away from the heat of the exhaust stack.

Anxious to get back home to work on this. Stay Tuned!