Fuel Vapor Check Valve Substitute

[txvepr]

So my Fuel Check Valve is not checking anymore.

 

Opening the gas cap releases a great amount of pressure, and I can hear the fuel pump getting pretty loud too after a drive.

 

The manual shows the 'Fuel Check Valve' inline from the vapor canister back to the fuel tank, and after checking it it seems to not be working as desired.

 

Have replaced gas cap recently.

 

'Air does NOT flow smoothly'from the engine side when I tested it.

 

I have not found one available or listed at any auto store, and Ebay returns the Brake booster valves on a search.

 

Does anyone know of a substitute part # that will work? They don't look too complicated and surely other brands used something similar?

 

Please let me know, I can't have my fuel tank explode on me on the way to work!

 

Thanks.

[71Nissan240Z]

Did u verify the line isn't clogged? I mean the one from the engine bay to the tank? Sometimes critters will crawl in there and nest if it's left open to elements. Disconnect from the tank side and run compressed air to see if u can blow anything out.

Your tank won't explode...it will implode. For now leave the cap a little loose and do not fill the tank very much past half.

Edited March 26, 2015 by 71Nissan240Z

[Stanley]

Don't know about your car, but 240z has a "flow valve" on the left side of the engine. It has three inlet/outlets. One goes to the crankcase vent, one to the stock air cleaner, and one to the hard line that goes to the expansion tank. There's a procedure in the FSM to test it. My flow valve didn't work until I gave the insides a good blast with carb cleaner. You have a totally different setup I expect; maybe there's no way to clean the check valve. The steel lines can be cleaned by working a braided steel wire through them (attached to an electric drill) and then washing them out with alcohol or maybe fuel injector cleaner.

[FastWoman]

Stanley, this is a weird little check valve with two nipples.  Air/vapor passes freely in one direction, but may also pass in the other direction with a bit more force.  Thinking mine was defective (for passing air in the reverse direction), I looked for a replacement and couldn't find one.  I then determined/figured it really wasn't defective after all.  It was simply a weird part.

 

In a pinch, maybe you could substitute two check valves plumbed in parallel with each other and flowing in opposite directions, so that some resistance to flow exists in both directions, but air may pass either way.  Preferably one check valve will require a bit more force to open.

[txvepr]

Wanted to give an update on this to anybody who cares.

 

Symptom was my fuel tank was getting pressurized after running. If I opened the cap, I would have a huge rush of air coming out of the tank. I could also hear the fuel pump start to get louder or sound like it was working harder.

 

I replaced the "fuel unit assembly part 17331-N4200" ,which the service manual calls a fuel check valve btw. I found a NOS one on ebay.

and

This has solved that problem. No more pressurized fuel tank, fuel pump sounds happier now. I don't know what else will return to normal at this point, but it can't hurt!

[Captain Obvious]

Cool. I'm glad you were able to find NOS, and I'm hoping that it's not going to become the next part that will fail on all the fuel injected cars (like mine).

 

I'm thinking your old valve is gunked up inside with crud and you might be able to clean it out and keep it around in case you need a spare. Failing that, are you gonna take it apart and see what went wrong?

[Redwing]

What year is your car? I am having the big whoosh rush of air too, on my '76 280Z.

Trying to figure it out.

[SteveJ]

17331-N4200 is used in 76 and later. Courtesy Parts lists it as NLA, but Nissanparts.cc doesn't list it as NLA (though they might list less information than they previously would). NissanPartsDeal.com might have it, but they say to call to verify. A few other places claim to have them, but I don't know the veracity of their listings/websites.

[Zed Head]

Where is the check valve located?  I see that it's in the vent line, but haven't seen its actual place on the car.  I've never had my side panels off to look at the reservoir and lines above the tank.  Afraid I'll crack the panels getting them out.

[FastWoman]

Zed, if we're talking about the same part, mine is a little plastic doodad, about the diameter of a quarter if I recall correctly, mounted to the bottom of the car in roughly the same vicinity as the fuel pump, just prior to the hard lines.

 

Redwing, pressure in the tank is normal.  The whoosh is normal.  Too much pressure and whoosh is not.  If the check valve is functioning properly, there will usually be some pressure in the tank.

[Redwing]

On my Z it is a HUGE whoosh.

[Zed Head]

Thanks FW.  I think I know where it is now.  Found another drawing in the FSM.

 

I'm pretty sure I've checked the check valve function from the engine bay in the past.  It seemed to have a one way action and I thought I knew what I was looking for, although, looking at the drawings, it's not clear to me what it's actually designed to be checking.  But I get no whoosh at all.  Might have a slow leak down to the charcoal canister.

 

Redwing, it could be that somebody removed your charcoal canister and blocked the vent line.  The canister is about the size of a gallon coffee can and sits right next to the radiator, passenger side.  It's black and has three small hoses connected to the cap on top.