Gas Pump Problem-Evap Emmissions Check Valve

Ever since I purchased my 355, I have always had problems putting gas in the car. What happens is the pump always kicks off after a few seconds. I have to dribble the gas in slowly to make it work or hold the vapor recovery hose off the nozzle to vent the fumes.

Note: I live in St. Louis and the gas pumps have the vapor recovery hoses which are supposed to help smog. It works well in other areas (without these vapor recovery hoses) as the fumes can vent out the nozzle.

I did some "searching" on FerrariChat and found a few different responses from "THEY ALL DO THAT" to "They are NOT supposed to do that". I tend to agree with the latter so I started digging into it. See the attached drawing. The way I understand this to work is when I put gas in the car (assuming the car is not running), the vent on the gas tank (GAS VENT TUBE) should vent the "gas fumes" through the Roll over shut valve (5), through the 2 way breather valve(4) and into the acrivated charcoal filter. At this time the Canister Purge Valve (3) is closed and the fumes are held in the filter. Once the car is running and most likely under certain conditions, the Canister Purge Valve (3) opens and vacuum draws these fumes into the intake and they are now "purged" from the system.

Is this correct? If it is, I found my 2 Way Breather Valve (4) (I call it a check valve) installed in the wrong direction. That is the gas fumes reach the check valve and stop. The bad part is this also means when the Canister Purge Valve (3) opens, it could actually suck gas from the tank assuming there is enough vacuum. Maybe that is why I get such terrible mileage (14-16 mpg no matter how I drive).

Before I change anything and drive I want to make sure I am looking at this properly. I value all of your input.
View attachment Evap Emmissions A.pdf

 

I haven't had a problem yet with the nozzle shutting off and we have vapor recovery in CT. And my gas mileage is identical...

 

I can't help directly, but, if you do something that puts a high vacuum on the tank itself, the problem isn't that you might suck some fuel out into the intake tract -- the problem is that you might implode the tank (so you are right to be cautious).

When you say that you found the 2-way valve installed backwards are you basing that on the visual comparison of what you have to the OM figure and the SPC figure?

I'm the first to say that some of the F technical English translations are downright terrible, but "2-way" implies to me that there is flow allowed in both directions under some conditions (i.e., it isn't a simple one-way check valve) -- have you tried sucking and blowing (no jokes please!) both gently and strongly on each hose connection port of the 2-way valve?

PS I'm a little doubtful that the entire air volume of the empty tank is forced thru those small lines (or that they could handle such a high flow rate or that the designer wanted this displaced air running into the intake tract and thru the non-running engine). It would be more straight-forward if the displaced air was meant to come up the ~19mm line that runs parallel to the large fill line -- are you sure this ~19 mm line is unkinked/unblocked? Also, where it rejoin the main fill line near the fill cap -- is this above where the end of the filling station nozzle reaches?

 

The problem is, I believe, caused by the cast fuel filler used by Ferrari that is narrower than the fabbed steel ones used in other brands. This narrower inlet tends to cause some gas/fuel/petrol (depending on your accent ) to splash around and back at the nozzle. The more sensitive ones detect this and shut off.

My Mondial t does it, my 355 did it. I do have a local Shell gas station here in Simi Valley where the number 5 pump is better than the rest. I always wait for that one.

FWIW my wife's Mazda MPV is just as bad as the Ferraris - it has a 90 degree bend in the filler nozzle just after where the pump spout would reach. The Miata was perfect however.

The check valve in your car may be the wrong way, but I don't think it will make any difference. Oh.... and your mileage will still suck, although 16 is pretty good if it's a 95

 

Looking more into the this, I found my "2 way valve" (which really is a one way check valve) is backwards. The detail on the manual proves it as did my "suck and blow" testing. I have yet to test my solution at the gas station but I may have to agree with lusso64 that the nozzle design may be the biggest problem as some gas pumps are less of a problem them others. Thank you all for your responses. I will keep you posted as to what I find on my next fill up.

 

My check valve was definately wrong. Now I have NO problem with ANY gas pumps (at least 2 for 2) and I do not get the "WOOOOOSH" sound when taking of my gas cap. For those who are interested, the RED check valve in this picture is INSTALLED CORRECTLY. My was upside down and wrong since I bought it used 2 years ago. How long before that it has been wrong I do not know.

Thanks for all of your help!!

1997 Ferrari F355 Spider (6 speed)
Image Unavailable, Please Login

 

Are these valves on 360's as well, and if so where? Mine takes forever to fil and I would like to check this out. Thanks.

 

I do not have the schematic on the 360 but I can tell you ALL cars (post 1996) use a system similar to what I have. If you can get me a schematic I can probably help you chase your problem.

 

The picture shows the valve inverted from the image in the service manual. Can someone confirm that this is correct? I was getting the "WOOOSH" sound when I opened my fuel cap, but starting today, I no longer hear it. I have not changed anything. I also have a 1997 F355 Spider, but my valve is facing the opposite direction of the one in the image.

 

I still have my valve as shown in the picture and I have had no problems and NO wooshing and I am going on 2 years since I posted that thread. It it possible the check valve is no longer working? I would pull it out and verify. You should be able to blow on it one way but not the other. (Or suck one way and not the other). If it is no good, I would believe at some point you will get a check engine code but without checking into it further (testing) I can not verify.

I believe my valve is in the correct position and my car has been running flawlessly since.....no wooshing and no check engine lamps.

Mark Manzonelli

 

We've seen this problem too with 360's where it ended up being the activated charcoal filter too plugged up. That is, with all valves working properly there was not sufficient flow through the canister to vent the tanks while filling up with gas.

Also on the 360 there are check valves at the top of each tank. If you smell fuel, chances are on or more is cracked. Ferrari has an updated version. The whole spider top section has to be disconnected and moved up with a hoist to get to them on the spider model!
Image Unavailable, Please Login

 

at the risk of being irrelevant, i have similar problems fueling my 328.
most filler hoses will try to spill fuel back up the neck if i try to pump too quickly.
i cannot use the autofill feature at any gas pump. it will simply kick off.
i really hate spilling fuel on the car or letting it run down the cavis hose.
must be a "ferrari" thing. interesting though, my gmc pickup has the same problem.