What exactly does this thing do? To go into more detail this valve is right next to the canister with 3 ports and I'm curious if it could cause the car to have vapor lock or cause it to hesitate at the begining if it was bad. I'm trying to eliminate everything that could cause this hesitation and so far I've checked almost everything and it seems GM disconntinued this part and I havnt had much luck finding it, which sucks. I found one at the junkyard and tried it but I have no clue if it's good or not. Is there a way to check if they're good? Anyways thanks for any comments or suggestions.

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1986 Pontiac TA 305 carb.
K&N Open Air Cleaner
B&M MegaShifter

Future Mods:
3.73 gears
Nos
TransGo Shift kit
Edelbrock Perf. Carb.
Edelbrock RPM manifold

Cool car for being my first and spending $1000 at an impound auction. Had to start it with a screw driver for a bit but it's all gravy.

 

i believe you mean the negative relief valve (wich is exactly what it does).
to check just put the pipe side on your mouth and try to suck, it should be free to suck and impossible to blow, if is not exactly as that: it is u/s.
feel free to e-mail me if you have any questions
fernando.

 

Jus to clarify, on the diagram it says Tank Press Control Valve and there is 2 going out, I think one to other vacumm hoses and one going to gas tank, and other is going to canister.

------------------
1986 Pontiac TA 305 carb.
K&N Open Air Cleaner
B&M MegaShifter

Future Mods:
3.73 gears
Nos
TransGo Shift kit
Edelbrock Perf. Carb.
Edelbrock RPM manifold

Cool car for being my first and spending $1000 at an impound auction. Had to start it with a screw driver for a bit but it's all gravy.