Fuel line replacement, check valves and limiting fire damage

[Hoody]

Brilliant! Thank you Wildthings!

[furgo]

[BUSBOSS]

[furgo]

Would then the installation with the non-return valve look like something like this?

And to make sure I understand the operation with the valve allowing flow only in one direction, where would fuel be in each one of these situations?

That is, which lines/parts would be full or empty of fuel at which times?

Last but not least, reading up a bit on the fuel pump, I've noticed that the electric pump already has a check valve built in. Would that not make an external check valve redundant?

Thanks.

[Wildthings]

The lines are full of fuel at all times. The lines from the pump to the regulator even have pressure at all times

The object of the added check valve in the return is to prevent fuel from flowing backwards out of the tank towards the engine once an engine fire has started and the hoses, particularly the return line from the regulator to the tank, have been compromised.

It would actually not be a bad idea to have a marine anti-siphon valve in both the supply and return lines located as close to the tank outlet and return fittings as reasonably possible, note that a MA-S valve would function somewhat differently in the supply than in the return. If a fire starts, say by the CSV spraying fuel at the distributor you want the fuel supply to stop totally once you turn the key off or the engine otherwise dies. If the fire has compromised the fuel lines then with a stock setup there is not way to stop the flow and you get a fire that is pretty much uncontrollable which quickly engulfs the entire vehicle.

[furgo]

Thanks a lot for the answers.

So a couple of points to make sure I got it right:

[foxmon]

There are additional hoses, line and filter for the BA6 heater, if you are lucky enough to have one.
_________________
'78 CEII Deluxe Westy Auto 2.0 FI Hydro now w/'79 heads
Bus driver since 1975

[Wildthings]

[BayCreamPuff]

I have my check valve installed on the return line right before the nipple on the tank. https://www.amazon.com/dp/B0169LE31K/

_________________
Cream Puff
'79 CA Stock FI Deluxe Campmobile

Earl Grey
'87 GoWesty 2.2 Westfalia

Marsha Mellow
'00 Eurovan VR6 Full Camper

[Wildthings]

[Iain]

[furgo]

[furgo]

Trying to summarize the thread regarding check valves, the suggestions are:

• Add a check valve near the tank inlet on the return line
• Add a check valve near the tank outlet on the supply line

The installation would look like this:

Return line

The purpose of the check valve on the return line would be to avoid gravity-fed fuel to flow from tank to engine during a fire.

If it is to be installed near the tank outlet (on a '78-'79 bus at least), a length of the metal pipe between fuel pressure regulator and tank inlet would probably need to be cut off to allow for the extra length of hoses and return check valve.

BayCreamPuff, is this what you had to do on your installation?

Supply line

The fuel pump already has a built-in check valve to keep the system pressurized when the engine is not running. In theory, it would keep the fuel from siphoning back to the tank, but if it gets compromised in a fire, an additional check valve on the line would add an extra barrier to stop the fuel flowing to the tank.

However, I've got two questions on this:

• In case of a fire, as the tank sits above the engine level, there is no way to stop gravity-fed fuel to flow towards the engine, is there? Or would the fuel flow get stopped before the pump given that from then on it'd have to flow upwards and it could not be pumped with the fuel pump off?
• Which situation could actually cause the fuel to flow back to the tank on the supply line?

Thanks.

[bbrowncods]

• In case of a fire, as the tank sits above the engine level, there is no way to stop gravity-fed fuel to flow towards the engine, is there?
If you had a check valve on the supply side with the added feature of being spring loaded to prevent flow that is set above the head pressure of a full tank (1-2 psia maybe?).
Or would the fuel flow get stopped before the pump given that from then on it'd have to flow upwards and it could not be pumped with the fuel pump off? Depends on where the rupture in the line is (before or after the pump).

• Which situation could actually cause the fuel to flow back to the tank on the supply line?
Other than the pump running, there is no way fuel would go back to the tank. It all depends on where the breach in the line is as to whether a check valve will help, and if the pump is running or off.

[Wildthings]

[furgo]

Thanks for the clarifications, so to recap the "check valves at tank inlet/outlet ports" suggestions again:

Supply line check valve:

• Purpose: stop gravity-fed flow in the forward direction from the tank
• Requirements: spring-loaded check valve with specified cracking pressure (*) higher than upstream pressure from the tank inlet to valve when the fuel pump is off and the tank is full, but low enough so that the fuel pump can provide enough suction to open it.

Return line check valve:

• Purpose: stop gravity-fed flow in the backward direction from the tank
• Requirements: check valve with a specified backflow pressure higher than upstream pressure from the tank outlet to valve when the tank is full.

That's sparked a couple of other questions:

• Does anyone have experience with installing the check valve on the supply line? If so, what was the minimum cracking pressure you took?
• Might such a valve at the suction end of the pump affect its operation due to the added pressure drop?

(*) The minimum upstream pressure required to operate (i.e. open) the valve in the flow direction (note for those, who as myself, hadn't been exposed to check valves before).

[Wildthings]

[furgo]

Thanks for the answers.

[Dogo]

Great thread. Very interested in this topic as I'm paranoid about my bus catching fire. Unfortunately I'm ignorant when it comes to this stuff.

A couple of questions.
Would this work equally as well in a non FI, upright engine situation with no fuel return?

Would this effectively work as well as a cut off solenoid valve?

Does the vent canister placement -and it's hoses- in the engine bay compromise the chances of fire (relocating it a good idea?)?

Thanks in advance

[Wildthings]