vapour lock

[azruss]

From my personal experience. Most of the fiats I have owned released a vaccuum when opening the fill cap. My current 80FI doesnt. the fuel system is entirely stock. car runs and starts without any issue, clear up to temps to 105 F. I'm not willing to abuse myself at temps higher than that, but my garage is usually at a higher temp than outside.

[geoff]

it is interesting that you say that, because I also have a 1995 FIAT Coupe and it has a very strong positive pressure (not a vacuum) when the filler cap is opened.

[perthling]

Geoff

If the emissions control equipment (eg canister) is operating properly there should be no pressure in the Spider fuel system. I removed the canister on my CA car when it arrived in Australia and naively sealed the fuel tank lines to the canister. After experiencing pressure issues I put a small vent hole in the return/overfill line of the tank.

I have had starting issues at times, I have actually found that the ignition switch can be a cause also. Might be a long shot but worth investigating because my symptoms always coincided with hot days.

I also experience high pressure with my 1997 Fiat Coupe 20VT. No issues with performance though!

[76was124]

I too have been trying to get a description of how the system works for 3 years. But nobody on the forum seems to know, so I just have my own analysis (fwiw) from examining the diagram: The only way make-up air gets into the tank is through the cap on top of the canister, down through the canister (intentionally picking up the gas vapors from the charcoal) and on through the tubing and 2 way valve, the liquid/vapor separator, and hence into the tank through door # 1,2 or 3. (Why they made 3 lines coming out of the separator remains a mystery to me). So if you have vacuum in the tank, something along that line from the canister back to the tank is blocked. The engine should actually slowly die out, unless there is another source of make-up air. (I think I have read that POs with this problem went and drilled small holes in their sealed gas caps to try to "fix" the problem). I tested my system, with the engine idling, by removing the small plastic cap on the top of the canister, holding my thumb over the hole to block the flow of air, and seeing the engine slowly die and eventually it would have stalled. Remove thumb and it runs correctly again. Likewise, when you gas up the tank, the air has to go somewhere. It either leaks past the fuel nozzle and pollutes our beautiful planet with unburned HCs, or it goes back through these same lines and through the canister, where presumably the charcoal captures major portion of the HCs. The part I haven't figured out is how it regulates the flow of air from the canister cap through the canister and up in to the intake manifold. I believe that this is where the 2-way valve comes in, regulating the flow by balancing pressure and intake manifold vacuum. Otherwise, this line to the intake manifold just looks like a big vacuum leak. So this part I still ponder. Maybe someone else knows more on this?

I agree with Pete on how this system "Probably" works. For sure you need venting in two directions, which is why I think the description of it as a two-way valve as stated in the service manual (vs. A one-way valve from Auto parts supliers) is correct.
Filling the tank vents out THROUGH the canister, and air drawn by fuel pumping out to the injectors must come FROM the canister.

I read a post where Brad Artigue said the cap on the charcoal canister has a metered opening size. That's why running it wide open, or plugged causes problems. I've tried it both ways,same results as Pete. So unless you have a leak in your vent line, capping the charcoal canister will need indeed result in an eventual engine stall or very poor idle.

That being said Geoff, I agree with majiwrench as I don't think that's your, 'won't start hot problem', otherwise you would have stalled while running.

More likely Coolant temp sensor, unless you don't have spark..then ignition or other FI circuit problems. Brad Artigue's manual at http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf will give you some troubleshooting tips.

[geoff]

Sedona is up there is elevation, so doesnt suffer from the torrid temps we get in Phoenix. My 80FI has had no start issues during the summer, so the cars can take the heat okay. I agree with others the dumping water was just coincidence. The first thing i would check would be the vent hoses in the trunk and the gizmo that the hoses go into. The other possibility is the injector/injectors are leaking a little and flooding the motor.

Interestingly, I got my spider (a red one) from Sedona about 15 years ago (perhaps you even know it) so it should be well used to teperatures much hotter then here in its new home in France.
Geoff