Tank Venting Question

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RRoller123
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Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Tank Venting Question

Post by RRoller123 »

I have a 1980 FI Spider 2000 and I am unsure about how the tank is vented for makeup air. Do these FI systems use a venting gas cap or is there some other valved source of outside air? I am not sure which cap I have installed: It has a small pinhole in the center, but the rubber seal seems to allow no way for air to enter the tank.

Here below is a pic of the cap, any assistance is appreciated. Thanks!

Pete

Image
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle
bberry

Re: Tank Venting Question

Post by bberry »

RR,
Please read my last post on my emissions control removal.
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RRoller123
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Joined: Sun Nov 13, 2011 2:04 pm
Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Re: Tank Venting Question

Post by RRoller123 »

Thanks, I will check it out.
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle
User avatar
RRoller123
Patron 2020
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Posts: 8179
Joined: Sun Nov 13, 2011 2:04 pm
Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Re: Tank Venting Question

Post by RRoller123 »

OK, thanks for the thread lead. So it sounds like the 80 FI does not use a vented gas cap. But I still am unsure where the makeup air comes from? Are you saying that it gets pulled in from the charcoal canister by slight tank vacuum? A clogged or partially clogged canister would then allow a small vacuum to build in the tank and restrict fuel flow to the pump. I persist with this because my car will run great for about 45 minutes and then starts to miss and very slightly stumble until I push the gas pedal hard. Last night I drove about 20 minutes to cruise night, stayed there about 2 hours, ran the engine at idle for maybe 15 minutes while there, then drove back and it starts missing halfway home. Consistently does this. Seems like fuel starvation to me.
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: Tank Venting Question

Post by BEEK »

easy way to diagnose the vent problem, leave the gas cap loose or off, and drive it :)
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
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RRoller123
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Posts: 8179
Joined: Sun Nov 13, 2011 2:04 pm
Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Re: Tank Venting Question

Post by RRoller123 »

Right, but I need to know where the likely fault is to fix it.
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle
bberry

Re: Tank Venting Question

Post by bberry »

RR,
When it is bothering remove the gas cap and if there is a vacuum sound then the tube going forward to the charcoal canister may be plugged or the canister itself may be plugged. Just unhook it temporarily and see if that solves the problem. Also try what Beek suggested with the cap.
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RRoller123
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Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Re: Tank Venting Question

Post by RRoller123 »

So if it is correct that makeup air gets back to the gas tank via the charcoal canister system, I will focus my attentions there. I suppose also that the 2-way valve or the liquid/vapor separator could be clogged as well as the canister itself or the lines.

Can anyone on the forum describe how this canister system is supposed to work? Does air/liquid/vapor flow both directions based upon engine vacuum? Not sure what the 2-way valve does. The name imples flow in both directions. It seems as though the canister would pull OUT of the tank based upon it being hooked up at the other end to engine vaccum.

Image
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle
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