This is my daughters 92 245

I just discovered a fuel leak at the tank return line on the fuel rail. I checked for pressure in the tank by opening the fuel cap and sure enough there was a good bit of pressure that was released. It continues to build pressure after it was released

Does this sound like a faulty fuel cap or is there something else I should check?

Fuel is coming out of the return line and looks like I will need to replace the last couple of feet. What size is this line? Any tips are appreciated.

Thanks
Dan

The line from the gas filler neck to the vapor canister is plugged or restricted. What would be a good way to try to clean and blow out this line to improve airflow.

I rigged a tire pump to work after applying some carb cleaner to the line,the pump quickly trips off so it is plugged, is there a one way valve in the line?

I checked this line on my 93 and can easily blow through it, so I assume this is correct and I have a blockage in my 92's plugged vent line.

How is the vent line run between the carbon canister and the fuel tank fill tube?

Thanks
Dan

I followed the vent line from the charcoal canister to a device mounted above the differential that has one line in and one out. I'm not sure what it is or where it goes but appears to be going towards the fuel tank.

Looking for a blocakage in the vent line to the gas fill tube to the tank.
Sure would appreciate some ideas!
Dan

Hi Dan,
I got ideas but who’s saying how many are goood?

I’m not too knowledgeable either when it comes to what’s above the gas tank. I never had one down or took the time, in the junkyards, to pay attention.
The yard jerks do punch holes in them here, so not much need too.

The fuel cap itself is a one way check valve to let air in as fuel is used.
I know I can suck air through the cap by mouth but not blow it back.
I think it must be up a ways and therefore that’s why they make a tester for it alone.

I think if the tank does get up in pressure, from time to time, you can hear in the car a burping sound for a short time. I have always thought it was the cap.
The canister line probably fastens to the filling tube pipe and should only carry vapors to the evaporative emission canister from the fuel tank.

The only other valve I know of to be on top of the tank is a roll-over valve that cuts the fuel supply to the fuel pumps inlet.

Have you removed the gas cap while checking that line?
Just had to ask, as in, like one does with an electrical powered appliances troubleshoot.
Has the gas tank been removed as it could have gotten kinked?

Now on top of the canister, there is vacuum controlled valve that opens the canister to the intake manifold suction.
Under certain idle conditions or other of high vacuum situations in the manifold it gets opened to vent the canister and that tank supply line, as a flow.
That valve can get plugged up but can be rinsed out with some denatured alcohol, that you don’t drink. (:( Or even, that leftover of a beer from a visiting buddy’s glass. (:-)


Phil

If you can try to visit a wrecker I doubt you'd have much trouble finding another as they are not a part that's likely to fail. If you start looking at other vehicles you may also find that other cars use the same part. I can;t verify if the Volvo one is unique but I recently saw another post on a Porsche forum where the comment was made that most manufacturers used the same carbon canister.

On my 740 it's down behind the drivers side headlight and there is an airline into the hose just past the AMM that is involved. Its fairly small diameter so maybe it can plug?
It's all part of the pollution control system and probably possible to disable it by making the cap leak intentionally. best to fix it, better for the environment and that can make it fail if you need to do emissions testing. they got rid of emissions testing here but they used to always check if the cap leaks. if you want to be sneaky you can probably use a leaky cap and swap the good one in to pass any testing, but that's not really the "right way" about it.

My 66 doesn't ave anything like that. Never did. I think if you go back a bit further you might even find ground tubes where the crankcase smog could oil the road instead of making you buy new air filters ;-)

Thank you Phills!

I am able to blow through this vent line to the filler neck on my 93, so I assume that is how the line on the 92 should be also.

I crawled under the car and followed the vent line to this device just above the differential. Don't know what it is or what it does, so I guess I need to disconnect it to see if it is blocking the air flow. I can't blow through the line from either direction.

I have had 6 of these 240s over the years and never had an issue with the canister or the lines and apparently neither has many on the BB either! It looks like I will have to figure it out myself but how complicated could it be!

I have a picture of the device I can email if anyone is interested

Thanks
Dan

Its possible to post pics here but I dont know how yet.

on my Volvo 122 there is a thing above the differential with three lines to it , but those are brake lines and it's a pressure accumulator I think , basically a piston with a spring behind it all sealed into a unit that never seems to fail. my van has a brake proportioing valve and it leaked and it has rear drums.. its near the reservoir.

I think the 240 doesn't need that brake accumulator as it has 4 wheel disks.

there might also be basically a brass block with 3 brake lines, it has a spool and if one side of the split braking system has fluid loss the piston shifts, a switch reacts. and turns on the brake warning light. I think that one is on the firewall or near the brake reservoir.


I'm curious what this thing is. often the canister is in some out of the way place and outside the car.. some are tucked away under a fender. I can't think where it is on my 240. I have an 89 someone will know this.. the cannister is probably about the size of a 1 lb coffee can and if that isn't in the engine bay you can probably follow the thin PVC ( not rubber) line from just past the Air mass meter to where it is.

the fuel tank makes pressure sometimes, or maybe vacuum too. so it vents through the charcoal and then the manifold vacuum pulls air from the canister. There might be more to it.. maybe also a larger line. those lines may leak and that might cause poor running because any air that can enter without the AMM seeing it will cause the injection system to not inject the fuel needed to keep the balance of air fuel mixture.

under the drivers seat there will be a fuel pump and the filter. its on a bracket with rubber mounts.. It pressurizes the fuel fed from the pump in the gas tank. sends it up to the fuel rail and there is a return line, any fuel not used is allowed to return back to the gas tank. there might be a check bvalve somewhere in that system.. ?

a fuel pump doesn't "make pressure" not exactly, because it needs fluid resistance to have pressure , the fuel rail has a pressure regulator that maintains a certain fuel pressure and I think that is adjusted by the amount of vacuum in the manifold, more vacuum , more fuel pressure. the engine sucks harder and it gets fed more fuel the rest returns to the gas tank. I think that's basically how that works. in laymens terms.
vacuum is weird though, taking your foot off the gas increases vacuum. engine is "sucking" but throttle plate is closed, that creates more negative pressureinside the manifold, I think..

I remember having an old truck with vacuum driven wipers and it would stop wiping sometimes and I'd have to lift off the gas to get them to run ,so I could see. I was increasing the vacuum by lifting off the throttle.

I found this roll over valve https://images.matthewsvolvosite.com/rollover-valve.jpg and will take it out tomorrow to see if it is plugged and try to clean it out if clogged.
Dan

As I recall, inside the rollover valve above the diff is basically a ball bearing in a Y channel. If you're concerned about a blockage there then before going to the effort of removing it, maybe try tapping on it hard to see if that loosens the ball and restores flow. That would confirm a sticky valve. Are you sure that's on the vent line? I always assumed that valve was on the main fuel line to the engine. I guess on the vent line makes a bit if sense as you don't want a turtled car leaking gas at the cannister or a pulled off hose..
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

It is definitely on the vent line from the carbon canister to the gas filler neck.

The valve was stuck, the metal line from the valve to the filler neck was plugged,corroded, and broken.

The plastic line from the canister was also plugged solid, all blockages were removed with a liberal amounts of carburetor cleaner and blasting from my tire inflater.

This is still a work in progress as I need to finish connecting the line between the roll over valve and the filler neck as a foot or so of the metal line had to be cut out.

Hopefully this will fix the tanks pressure issue.
Thanks
Dan

where is that rollover valve located? I've never heard of it.

It is mounted on the divider between the fuel tank and the differential.
Dan

If you keep getting pressure build up in the tank that can only be released by loosening the cap then it sounds like you may have something awry with the evap system - clogged charcoal filter, collapsed hose or metal tube somewhere or …… ?

Thanks Chris, I have never had problems with the carbon filter or evap system are there any tests or observations that would help me locate a problem.
Dan

OK, I took the carbon canister off and found one of the vacuum lines was split. Guessing this will fix my pressure issue.
Thanks
Dan

Fuel tank pressure was not relieved by replacing vac hose?
I took canister out and can blow through the canister inlet from intake, I can actuate the valve with vacuum and then blow through the port labeled PCV. Imay not be able to blow through the very small hard plastic line from the canister to the tank filler neck.


This is a GM canister 17056292 am.
Dan

I had to replace a section of the return line on a 94 940t.

The original line was steel and I believe I was able replace that section with a piece of 5/16" fuel line. I don't know what the proper name is for it but it was a plastic line that was fuel safe.

I think I used compression fittings. I realize that isn't the proper/best repair but since it wasn't a pressure line I thought it would be fine and so far it has been- four or five years?

Randy
--
Any twenty minute job is just a broken bolt away from a three day ordeal

What is the best way to replace this rubber fuel hose returning extra unused fuel to the tank?

It looks the hose is about 2 feet long but I am unable to locate the line near the bottom of the firewall.

I would rather not splice this line for safety concerns.
Thanks
Dan

I did not see this addition to your original post. As I indicated the section of line I replaced was steel.

Randy
--
Any twenty minute job is just a broken bolt away from a three day ordeal

There is about 2 feet of fuel line at the fuel rail then it goes to steel to somewhere near the fuel tank.
Thanks
Dan