Fuel Vapor Check Valve Substitute

[Redwing]

Zed Head Thank you for explaining where the charcoal canister is located and size. I saw it immediately when I went to look for it, before I did not know size and placement. I do not know if it is functioning as it should, but at least I know it is there.

'71 Nissan 240Z suggested leaving the gas cap a little loose. I am going to try that today, as I have a physical therapy appointment, a longer drive. This is where she usually has stalling problems. Thank you '71 Nissan 240Z.

Folks, I am not experienced with this car. What I learned from Dad was way back in '71-'76. Only basic stuff, I do not remember fuel injection info at all. Thanks for your help, please try to 's plain so I understand.

[FastWoman]

Redwing, I think you could test your vent system (including the check valve) by doing the following:

 

1. Disconnect the fuel vent line from the charcoal canister.  It's the line that doesn't lead to the engine.  Instead, it leads to one of the metal tubes running from near the firewall to beneath the car.

 

2. Open your gas cap.

 

3. Wipe off the hose, and blow air (with your mouth) into it.  That's the air returning to the tank.  You should feel some resistance, but should be able to blow in that direction.  If so, the vent line is clear, and the check valve is letting air flow in at least one direction.

 

4.  Next, put the cap back on the tank, and blow more air into it.  You should feel resistance building as you pressurize the tank with your breath.  If that happens, good.  Now go and crack the gas cap, and there should be a bit of a whoosh.  If so, all good.

 

5.  Hopefully by now most of the gas fumes have left the vent tube, and you can try sucking air the other way.  This may be more difficult, but the air should vent in the return direction.  Be careful of the gas fumes, though!  You don't need to suck much air out, just enough to verify that the check valve will pass air both ways.  If that works, then you're probably good.  If not...

 

6.  Look for the check valve underneath the car.  It's a small, cheap looking black plastic part.  Remove it, and try blowing through it in both directions.  One direction should flow pretty easily, and the other less easily.  If it is good, then reinstall.  It should be oriented to let air into the tank more easily than out of the tank.

 

As I said before, there's too much about the fuel injection to explain to each and every person who comes along.  Nissan's factory service manual really is the very best resource you can study to learn this system.  I really mean that.  It's available for anyone to download absolutely free, with no obligations or strings attached, courtesy of the Datsun Z community.  The one for the 1976 280Z is here:

 

http://xenonzcar.com/s30/files/FSM/76_datsun_280z.zip

 

This is a zipped file, so you will have to unzip it.  Please let us know if you don't know how to do that.

 

An alternative is to buy a used manual online.  Here's one for $70 -- absolutely the best $70 you will spend on this car:

 

http://www.ebay.com/itm/1976-Datsun-280Z-Service-Manual-Shop-Repair-WORKSHOP-FACTORY-ORIGINAL-/151608238831?hash=item234c8e22ef&vxp=mtr

 

The introduction of the "EF" or "Engine Fuel" chapter even explains how fuel injection works.  It was written for people with nothing more than a knowledge of carbureted cars, back when fuel injection was a new thing.  There is very little we can do to help you if you don't equip yourself with some very basic knowledge of the fuel injection system.  Speaking the same language is essential in this process.