I sent my 3rd oil sample over the years to blackstone. This time they finally said there is fuel dilution. That's why i sent the first 2 samples but no dilution. I always thought gas would evaporate quickly anyway.

Alert: The tank won't take gas quickly, clicks off. Maybe that's a clue to my problem.

I've been very slow to fix this dilution / rich problem, I only drive 2000 miles per year. I did get a pocket oscilloscope last year to see what the O2 sensor is sending but never got to it yet. Car is not ODBC II. 5 speed. Only one 02 sensor. Volvo dealer parts dept sucks, wouldn't trust any O2 sensor info they'd give me.

About a year ago there was a small diameter 4 inch long rubber hose back by the tank connecting some pipes that head to the engine. Probably on passenger side. It opened up so I replaced it , didn't seem to do anything from a drive ability way. Perhaps that's when the fuel fill got a little worse. Any ideas on tank venting, single o2 sensor 850 , rich will be cool. 20 years ago they told me exhaust manifold had a leak, i hear that can make it rich, but rich running has only been for last 5 years. Original owner. 130k mile only.

We had an 04 XC70 that would be difficult to fill at the Gas station. After many conflicting theories I came across on this site, I decided to try one I found. The filler neck has a slender hose running up towards the fuel inlet. I detached this hose at a connection point while lying under the car and blew one strong blow from my mouth into the hose. Much resistance at first then it popped and was clear. Never had a fill problem after that. The theory is the some bug has nested in this location although that seems a strange place to build a nest. Fumes.

I have always laughed at that theory, nothing could live in that environment. But, something 'could' clog up the vent tube. I wonder what you 'blew' out? And why would it take years to suddenly clog up?

My 1998 did that and was 'fixed' by not filling up past the automatic shut off after a few tank fulls.

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Keeping it running is better than buying new

I'm waiting on warmer weather to check this out. Thanks.

If you ever go to NJ and have someone else fill the tank, that will explain it. An overfull tank will introduce liquid gasoline into the charcoal canister and vapor lines. That will make filling the tank 'slow' as the fumes have no where to vent. It also introduces excess fumes to the intake as gas fumes are released from the charcoal canister.

Drive around with 1/2 - 3/4 tank full as your max for a while, letting the system 'dry' out.

An aside note:

There are 2 fuel lines coming over the side of the engine. The return line has a flexible, rubber line at the end of the hard line. REPLACE the flexible line with a short piece of injector hose if the line is still original. These tend to crack at the 25 year mark and leak fuel = fire.

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Keeping it running is better than buying new

Well if the part is still available I'd get the molded volvo EOM hose. Anybody know the part #? My local volvo dealer sucks, the work like the wizard of oz not even letting me point at the part I want off the computer screen.

If the dealer would have the part, I suspect it would be dried out by now. I used a short length of 5/16 fuel injection hose (strong hose!) made by Prestone. You will need 2 clamps.

Because this hose is just a bit larger in outside diameter than OEM, the clamp must be placed over the bottom nipple before the hose is pushed down over same nipple. Then tighten bottom clamp. Top clamp is SOP.

On my car, I was having problem starting the cold engine - long crank times. I figured that it was draining back to the tank. It was, but because the return fuel line was just cracked enough to allow air to enter the fuel line and let the gas drain. Hard starts were cured with this simple fix.


On B.B.'s 1995 850, the line split enough to spray gas all over the engine and it caught fire - car totaled, and a melted mess. The rear wheels and spare could be salvaged, that's all.

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Keeping it running is better than buying new

I'll check out those hoses, makes a running rich problem seem trivial.

BTW: South Main Auto channel on youtube once mentioned there is a special hose he can get from NAPA for in-tank , claims regular fuel hose is not good enough for in-tank life. Thinks like that stick in my brain.

I haven't been filling my tank, but did once this year. NJ gas prices are higher than NY now, NJ has gone to the toilet.

Have a look at the hoses, vents, etc. associated with the charcoal canister. Fuel vapors are supposed to vent through there.
Greg