Location of one way check valve

[mullioni]

I am replacing the fuel lines in my 79 spider. The factory diagram calls for a one way check valve on the fuel supply line going from the tank. There isn't one located in my current fuel line. I picked one up from one of our vendors. Does anyone know if this is placed on the fuel line inside the trunk before the line exits forward, or is it mounted immediately after exiting the trunk before connecting to the hardline.

[ORFORD2004]

Back of the rear left wheel.

[DRUMMOND]

Its the small gray looking one

[AriK]

It's a 2-way check valve, a new one will have almost equal pressures on each end, blowing through it. There's a tiny one way check valve is on the return line near the carb.

[mullioni]

Thanks for the responses. I think you are referring to the two way valve in the vapor line. There are three lines that exit the top of the gas tank and connect to a vapor separator. From the vapor separator there is a single 7mm clear "Cavis" vapor line that is one of three lines that exit the trunk. Just outside the trunk, there is a two way valve installed before it connects to the hard metal fuel line. These were installed previously and are being replaced.

I am referring to the two fuel lines that connect to the sending unit and exit the trunk next to the vapor line. The Fiat factory manual shows a one way valve in the main fuel line and highlighted green in the first diagram. Mine did not have anything installed in the main fuel line. I do see the small one-way valve on the return coming off the carburetor. From what I have read, this is to keep fuel from draining back and assisting with starting.

DRUMMOND, in your photo, it appears you have installed a fuel filter in the main fuel line or is this in fact a one-way valve?

Here are the diagrams of the lines over your photo for reference.

[Funcar]

I think you may be talking about the white valve in the trunk. It is left of the electric fuel pump I installed.

[AriK]

My '79 did not have this valve installed when i refurbished all my lines. I think they are no longer available. Keep us updated how you proceed.

[mullioni]

Thanks Arik, I purchased one from Midwest before digging in and then finding out mine didn't have one. I would like to get it in the proper place. The trunk would make it easier if it ever needed to be changed and after looking at your photo, there are two holes in that area that were not used. Midwest has it listed under the original number shown on the Fiat drawing above #4362497. In the Fiat drawing it looks a bit like a spaceship and very much like the one in your photo. The new one is the all metal one in the photo w barbs. I will post a photo after I reinstall everything - tank and rear lines. I'm hoping to paint the metal lines tomorrow. I removed the 90 degree filler hose last night. Having the tank out and sitting in the tank opening made this a bit easier. I wouldn't want to take that job on with the tank installed.

[mullioni]

And you too funcar!

[AriK]

Also take special note whether there is improvement in cranking time after a couple of days of the car being parked.

[DRUMMOND]

Hi Mullioni

I guess I did not read correctly you first post? I just read the 2000 spider part. yes it is a filter for the fuel line. I found a different diagram for a 79 fuel line setup see if this helps you.

Here is the earlier years

[AriK]

Me thinks Drummond's diagram is more accurate for the '79. I noticed the check valve near the tank is replaced by the #4 check valve (pressure) near the fuel pump. My #4 has been omitted. There might have been a service call back in the day to remove them. I kind of remember seeing in the archives that they may have been the cause of engine fires but im not sure. Can someone confirm this?
Is it better to relocate it to the trunk area?

[mullioni]

Thanks. I'll have to take a look up in the engine bay.

[MIGHTY 8]

Man, this brings back bad memories!
I had this exact valve go bad on my 1980, and it took me close to a YEAR and several different repair shops to correctly diagnose its failure and correct it! That thing fails, and the whole car just falls apart with all kinds of misdiagnosed guesses! Valve timing..nope! Bad ignition coil...no. I mean at least in my experience this dragged on forever!