Maplebones brought this up in another post.
I'm getting ratty gas mileage in my 940 and it could be that "Midnight
Auto Supply" has been active in my driveway.
Maybe the ratty mileage is from worn hubs? I'll find out this summer about that.

Stant makes the standard OE locking fuel cap # 10591

Stant offers a "pre release" cap that lets the pressure out when you insert the key. That's #10501 This cap has a hinged cover for the keyhole that sounds good for the salt bath cars get here in the winter.

Stant has a nice online website https://stant.mypartfinder.com/
Check out the long cross reference parts list.
Volvo uses the same cap it seems for the RWD 200 series on through the AWD S70
and beyond.

I found the Stant 10501 at Ebay for under $15 shipped.
Autozone has a pair of no name caps for $12.99, maybe made in China?

The official sales pitch from Stant is that a faulty/worn fuel cap can allow up to 30 gallons of gasoline to evaporate in one year, yikes!

Bill

BB - I believe the fuel tanks are always vented to atmosphere in some way - either through a vented cap or a designed vent system? They should never have positive pressure internally?
Please correct me if I'm wrong here!

P.s. a locking cap is an essential!!

Ian F

The Evap.system takes car of any build up of pressure. Burns the fumes in a closed system when engine is turned on..

BB - I believe the fuel tanks are always vented to atmosphere in some way - either through a vented cap or a designed vent system? They should never have positive pressure internally?
Please correct me if I'm wrong here!

P.s. a locking cap is an essential!!

Ian F

Hi Ian,

"BB - I believe the fuel tanks are always vented to atmosphere in some way either through a vented cap or a designed vent system? They should never have positive pressure internally?
Please correct me if I'm wrong here!"

That's a good question that led me off to learn about the EVAP system.
In one post:
https://www.brickboard.com/RWD/volvo/1272348/940/960/980/V90/S90/troubleshoot_evap_systm_failed_ca_smog_test.html
The author indicates that the fuel system is sealed, and shows how a pressure
test starting at the filler cap can reveal failed fuel/vacuum lines leading
to failing the CA smog test and probably dumping fuel overboard.
He says: "the release pressure of the gas cap is about 3.6 psi"

Other posts indicate the tank pressure may vary positive and negative
depending on conditions.

One of nice replies to the EVAP post was from kittysgreyvolvo that offered more info:

Fuel Evap Test Failure: 1993 Volvo 240:
https://www.brickboard.com/RWD/volvo/1554479/fuel_evap_test_failure_1993_volvo_240.html

Failed Gas Cap AND Failed EVAP Canister Check Valve ..... with Images .... 200:
https://www.brickboard.com/RWD/volvo/1620115/220/240/260/280/failed_gas_cap_evap_canister_check_valve_images.html

Gates hose not the best quality yet may be more convenient to find. At least the Gates PCV and EVAP vapor line.

Info for charcoal canister / EEC replacements ... 200 1989
https://www.brickboard.com/RWD/volvo/980660/220/240/260/280/info_charcoal_canister_eec_replacements.html

Checking the EVAP system is on my to-do list when it warms up.

Cheers, Bill

Dear B.B.,

Hope you're well. If you wish to assess the condition of your 940's hubs, jack up the car, just enough that the tire is clear of the ground. Spin the tire with your hand. If it spins easily and noiselessly, the hubs are fine.

If, though, there's a grinding noise, that could mean: (a) a brake pad is binding on the rotor (which can cause poor mileage) or (b) a hub is "on the way out".

If you suspect (a), remove the tire and the steel pin, that holds the rotor to the hub. Then loosen the two 10mm hex head bolts, that secure the caliper frame to the strut housing. Slide the caliper off of the rotor.

See if the caliper pins allow the caliper to move freely. If not - if the caliper moves sluggishly or not at all - separate the caliper from the frame. Remove the caliper pins, remove any corrosion with a rotary wire brush, grease lightly with caliper grease and re-assemble. That should ensure the brake pads don't bind on the rotor. If the caliper pins are corroded into place, see if a penetrating oil (e.g., PB Blaster, Kroil, etc.) will free them. If that can't be done, replace the caliper and/or frame.

While the hub is unburdened by the caliper, try to turn the hub by hand. It should move easily and quietly. If not, the hub is at the end of its service life. There should be no "wobble" when you turn the hub.

Hope this helps.

Yours faithfully,

Spook

Hi Spook,

Thanks for the tips.
I'll be changing the original hubs with <212K miles this summer.
I'm delayed by waiting for my arm to heal after triceps surgery.
Then I'll know if it improves my gas mileage as it did with my 850.

Cheers, Bill

Dear B.B.,

I hope your arm heals smoothly and completely! How will that improve your car's gas mileage?

You might want to find a recent post, relative to torque values for hub nuts. You may want to have the work done by a pro. The force required to tighten to spec the hub nuts - specifically the 45° angle-tighten - may be more than you should try to exert.

Yours faithfully,

Spook

Hi Spook,

I can't use my left arm for too much for another few months, so even changing a tire is out for now. I should be OK to do this job by this summer.

Changing out front hubs in my 850 raised around town gas mileage from about 15
to 24 MPG.

Cheers, Bill

Dear B.B.,

Hope your recovery is fast and complete!!! Did the 850's hubs show signs of failure, e.g., grinding noise, when tire spun, or a "rumble" at highway speed?

I don't doubt at all that a hub - on the way out - will add to rolling resistance. But before a hub gets that bad, it usually makes noise.

Yours truly,

Spook

hi again spook,

i changed out the original hubs at about 215k they were not grinding, and i installed the cheap chinese hubs that did start to grind in less than 3k miles.
chinese hubs are rubbish.
then i installed FAG, german hubs and saw the mileage improve drastically.

i coulnd't find FAG hubs for the 940, but got SKF and think they are oe hubs.

the new locking gas cap is due here friday.
perhaps the gas mileage will go up after i install that ? ;-)
do i need to worry about any o-ring or seal at the filler cap?

cheers, bill