Uncle onlyVolvo,

How the fuel tank gas cap gasket or O-ring? Locking gas caps can excessively vent through the lock mechanism if it is a cheap locking gas cap.

I keep an official regular (non-locking) OEM Volvo gas cap with a new O-ring.

Mighty WA-state, the greatest and mightiest of all 50 states, tests the gas cap seal and you can fail if the gas cap leaks. A leaking gas cap will cause CA-state SMOG EVAP test failure.

Inspect the fuel vapor (what is called the EVAP system in CA smog and newer car vernacular) vacuum line piping from the fuel tank to the fuel vapor holding charcoal canister in front of the front left driver (US & Canadian market) wheel secured to the inner fender.

The EVAP recover line is connected at the top of the fill neck. You can see it when you remove the black plastic shroud in the trunk (or remove the passenger side [right as viewed from rear] cargo bay access panel as if you are going to replace tail lights).

Dunno if you have a sedan or wagon.

The fuel tank mounted EVAP vapor vacuum line may also come connected to the fuel sending assembly with power, fuel, and fuel return at the top of the fuel tank. You can access this through the trunk floor ahead of the hump below the rear hat shelf (pull up carpet, you'll see the grey galvanized metal plate).

Also, the fuel sending unit O-ring seal can lose a seal if old or some prior owner removed and replaced it and did not replace the O-ring.

WARNING: Access and removing the gas-tank-mounted fuel sending unit is DANGEROUS operation exposing you to highly explosive fuel vapors and fuel. Special tools are required to remove this part. Seek a qualified, trusted mechanic to perform this operation if you are not trained to do so safely using the proper tools.

You use the fuel sending unit bung removal tool (rent or get it from a parts house; FCP Groton may still sell this part) or use brass tools. Steel on steel impacts may cause sparks as you try and free or replace and secure the fuel sending unit to inspect the O-ring.

The rubber vacuum line sections and any clamps used to secure the rubber vacuum line connections are of particular interest for inspection. Check for loose clamp, rubber hose ends that are split, brittle, or disconnected.

You can use a hand-held vacuum pump to pull a vacuum on that side.

Inspect hose connections and clamp on the charcoal canister and remediate. Hose ends may be disconnected, may not make a good seal, missing clamps and the like.

Remove and inspect the charcoal canister. See any rust or corrosion that breached the housing? Replace it with a better used junkyard example or go $$ new. You may be able to use a petroleum vapor resistant adhesive sealant or JB Weld.

You may be able to use a vacuum pump, or with a hose section, blow into the input side of the canister or create a vacuum on the engine air intake side. I'm unsure whether a mechanical valve exist in the charcoal canister for late model 240. I've seen designs with no valve, as it depends on the charcoal to sequester the fuel vapor and the running engine air intake to pull a vacuum through the EVAP system reducing sequestered fuel vapor concentrations while perpetually drawing a vacuum to pull gas tank vapors as you run and move the car.

The warmer the weather, the greater the fuel vapor creation in the gas tank. The EVAP system is a truly useful thing.

Inspect the vacuum line piping from the canister output to the air intake. You have some soft rubber and hard (nylon) sections. The nylon may last the life of the car so far as it had not kinked or chafed against a harder object (metal) as the piping comes up from the canister, under the unibody frame rail, and into the engine bay.

You can replace faulty nylon sections, replace faulty rubber vacuum line with used (from another junkyard car, make does not matter, Euro and Japan makes use better rubber fuel vapor vacuum line). Replace clamps, and tighten to secure snug.

You may also want to inspect and review the entire air intake system piping. The usual suspects as posted all over brickboard when folks have an air intake leak. The air intake accordion bellows between the MAF/AMM and throttle body can chafe and easily leak. Inspect all unions and clamps that they are straight and secure and tighten to a proper snug.

Your CA-state Volvo may have an EGR system on it. You may want to inspect it at some time.

Have you recently checked the black plastic OBD-1 LED box on the driver side inner fender for codes set by the Bosch LH-Jetronic (socket 2) fuel deliver and the Bosch EZK (socket 6) ignition system. The EZK also monitors and controls the EGR system.

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

Merely service the EVAP system to pass CA-state SMOG and get your sticker.

Than inspect the rest of your 1993 Volvo 240.

A well tuned Bosch LH-Jetronic/EXK equipped Volvo, with all things working well, is a very clean burning car. IN fact, the better all emission controls work, all systems are buttoned up, the better the Volvo 240 B230 operates.

It is a myth disabling emission controls on the cars helps. Bosch and Volvo incorporated emissions controls as a part of these systems from the start so your Volvo runs well and efficiently while burning cleanly.

Questions?

Hope that helps.

Volvo "Technical Writing supercharged with Buttermilk" MacDuffed.