Fuel tank pressure build up??

[L31MaxExpress]

The vent is in the center, right next to it is the vent from the tank and the outer fitting to itself is the purge vacuum signal. It was just a 3/16" nylon tube to ported vacuum from GM. I changed both the rubber hoses from the metal line to the tank and the canister to the metal line and blew air through the metal tube allowing the tank to vent as it should.

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[blueburban87]

Only the really late model TBIs had a purge solenoid, the rest used ported vacuum. I hooked my purge canister up to manifold vacuum lacking a ported vacuum fitting through a Dorman 47311 inline restriction. Works great although my engine is in closed loop within 10-15 seconds after startup. The resticted fitting allows a slight and continuous purge on the canister while the engine is running. I do not have fuel fumes even recently with it sitting in a 100F shop with a near full tank for 2 weeks.

Mine is a 1987 G20 with a Proflow 4 injected cammed L31 350. Your 87 suburban should have the same setup. Canister on the front core support with 3 fittings. One to the tank vent, 1 to a breather cap (looks like a cap but it is a screened vent) and 1 that ran to ported vacuum from factory.

Not a bad idea. I was about to just remove all the lines and add a fuel filter to the vent line in the back of the tank to manage pressure and vapors. I may look into what you did first