Does switching from the regular twist off fuel cap that comes with the car from GM to a locking fuel cap not made by GM have any effect of causing the service engine light to come on. Does it some how effect fuel pressure?
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94 Formula LT1 (Aqua Metallic) - Auto. - 104,000 miles - Charcoal Leather Mods: Magnaflow Muffler, Lingenfelter CAI, MadZ28 Tune, 160F Hyp. T-Stat., 1LE Elbow, & Summit Cutout. Options: 155 MPH Gauge Cluster, & 255-50ZR-16 Tires. -
It will if you don't buy the correct cap, and if you drive an OBD-II car. Your 94 is OBD-I and will not set a code for a poor gas cap seal. Your stock cap was "unvented".... the replacement has to be unvented, and have a gasket that seals well to the filler neck. Whether its "locking" or not has nothing to do with it.
Pressure in the tank does not affect pressure in the fuel rails, since the system is a "closed" system. Both the suction of the pump and the discharge of the fuel return line are exposed to the same pressure. It will affect performance of the EVAP system - the charcoal cannister in the drivers rear fender, and you may notice the smell of fuel in that area if you don't have a sealed system.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor -
On the same subject, I think.
In the summer months when I park the vehicle after driving it I can here a weeezing sound coming from the gas cap. If the cap is removed a huge gust of gas vapor comes out.
This also happens when the tank is low and you remove the cap to refuel.
This just seems dangerous because I know the vapors are more explosive than the liquid gas it self.
Do I have a valid concern, or is this normal.
Im pretty sure I have the original cap.1995 Z28 Convertible, 350ci LT1 73K miles M6.
Dyno results: 301.5 RWHP 326.7 RWTQ
Performance Mods 4.10 gears, AS&M CAI, MADZ28 tune, Borla catback, RK Sport mid-length headers, LT4 valve springs, CC pro mag 1.6 RR's, LT4 KM, MSD OVC wires, TB bypass, 160 t-stat, SLP clutch plate w/Kevlar dual friction disk, 52MM TB, TB air foil, 1LE aluminum driveshaft, ASP UD pulley, LS1 brakes w/ Hawk HPS pads, LCA's and PHB.
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Thats what mine does with the regular gas cap, and the locking gas cap which I bought. Thats what injuneer called the unvented gas cap which my car needs I assume. I believe if you didn't have pressure when you take it off that wouldn't be good.94 Formula LT1 (Aqua Metallic) - Auto. - 104,000 miles - Charcoal Leather Mods: Magnaflow Muffler, Lingenfelter CAI, MadZ28 Tune, 160F Hyp. T-Stat., 1LE Elbow, & Summit Cutout. Options: 155 MPH Gauge Cluster, & 255-50ZR-16 Tires.Comment
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The closed system used in the 4th Gens has a pressure relief valve. The tank needs to be under a little pressure to force the fuel vapors out through the charcoal canister. When the vapor goes through the canister, the charcoal absorbs the hydrocarbon vapors, and allows mostly air to vent outside the system.
There is a pressure relief valve to prevent the fuel tank from building up too much pressure. From the factory diagram though, it appears the relief valve still dumps into the charcoal canister. If your charcoal canister is plugged up, or saturated with liquid fuel, it might possibly lead to excessive pressure buildup in the tank. Like I said, the diagram is not real clear, at least not to me, and all the parts except the canister are hidden out of sight, pushed up between the tank and the body, so its sort of hard to figure out exaclty how the system is connected up.
From Shoebox:
Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
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