Fuel regulator question

[GeorgiaGuzzi]

So I pulled the tank back off to attach all the breather hoses and the canister system I bought for the return goop from the breather system.

When I loosened the fuel hose that runs from the fuel pump to the pressure regulator it shot gas out rather spectacularly onto yours truly. (Yay for safety glasses!) Now (after a shower) I’m wondering if it’s supposed to have that much pressure on it. I certainly don’t remember it doing that when I took it off before. Could the pressure regulator be clogged up? A dirt dobber had set up housekeeping in the barn. I tried cleaning the barb out as best I could but am wondering if I killed the regulator instead. Or am I overthinking it? Not that I would ever do such a thing! 😂

[Kiwi_Roy]

I can't remember if it's 40 or 45 psi
http://dpguzzi.com/efiman.pdf
This document is getting harder to find, i'm sure it will disappear one day.
Note: the drawing shows the regulator attached to the manifold, that is not the case for Guzzi the vent is open to atmosphere.

[lucky phil]

So I pulled the tank back off to attach all the breather hoses and the canister system I bought for the return goop from the breather system.

When I loosened the fuel hose that runs from the fuel pump to the pressure regulator it shot gas out rather spectacularly onto yours truly. (Yay for safety glasses!) Now (after a shower) I’m wondering if it’s supposed to have that much pressure on it. I certainly don’t remember it doing that when I took it off before. Could the pressure regulator be clogged up? A dirt dobber had set up housekeeping in the barn. I tried cleaning the barb out as best I could but am wondering if I killed the regulator instead. Or am I overthinking it? Not that I would ever do such a thing! 😂

No it shouldn't do that BUT it looks like you have your manual fuel tap in the closed position. If thats the case it could well do what you described. The reg is 3bar which is basically 44 psi and thats what it relieves at back to the tank. Normally when the pump stops on shutdown the pressure relieves back through the pump as there is no check valve in the system to prevent this. If you shut the tap off while the pump was operating it wont relieve back into the tank. Either that or maybe the tap screen or pump feed is blocked or partially blocked or the feed hose was kinked or the tank vent is blocked or the filter is blocked.Whatever would cause the fuel pressure relieving back to the tank via the pump inlet.

Ciao

[GeorgiaGuzzi]

I can't remember if it's 40 or 45 psi
http://dpguzzi.com/efiman.pdf
This document is getting harder to find, i'm sure it will disappear one day.
Note: the drawing shows the regulator attached to the manifold, that is not the case for Guzzi the vent is open to atmosphere.

Thank you Roy

[Wayne Orwig]

If the regulator and pump does not leak down when shut off, it will hold pressure.

The bikes with the pump and regulator inside the tank can hold some much pressure for days, that it is nearly impossible to unclip the fuel line. You have to unplug the pump, and crank the motor to fire the injectors, to relieve the pressure just to got the fuel line unclipped.

Yes, the pump does have a check valve that can hold the pressure.

[lucky phil]

If the regulator and pump does not leak down when shut off, it will hold pressure.

The bikes with the pump and regulator inside the tank can hold some much pressure for days, that it is nearly impossible to unclip the fuel line. You have to unplug the pump, and crank the motor to fire the injectors, to relieve the pressure just to got the fuel line unclipped.

Yes, the pump does have a check valve that can hold the pressure.

Thanks for the correction Wayne. I revisited Roys link which I saw years ago and actually saved on my computer and yes the external pump indeed has 2 check valves. dont know if it's something I forgot or hadn't ever been aware of. I understand why the CV is on the inlet side (to relieve the pump case pressure when the pump is off and probably heat soaking) but the outlet one is interesting.Then again the inlet CV in a standard bike with an electric fuel tap wouldn't relieve anyway as the tap would be shut at rest.
The only things I can think of bearing in mind the pump primes the system as soon as the ignition is turned on is if the bike stalls and the ignition isn't cycled and therefore the prime function doesn't happen there is still some pressure in the lines to get a quick restart. Or maybe to hold some pressure after shut down to raise the vapour point of the fuel to prevent heat induced vapour lock or maybe it's for installations where the pump is higher than the fuel tank, dont know, but I'd like to. My external pump bike has never held pressure though I know that as I've pulled the return line many times just after shutdown to remove the tank and it has squirted any fuel.

Ciao