Why can I smell gas towards the rear of my Volvo S80 yet can't find a leak?

Answer 1

There probably are several possible causes. At the moment three come to mind. 1. The gas cap, which is supposed to "seal" the fuel system, is leaking vapor. 2. The fuel line from the tank to the engine has developed a leak, but it is so small, that the fuel evaporates as fast as it leaks, thereby not leaving a tell-tale wet spot. 3. The fuel return line [or vapor vent line if your vehicle has one] from the engine compartment back to the fuel tank has developed a small undetectable leak, the same as in #2. It is possible to have a small enough leak to not be easily spotted visually. yet under the right conditions of little or no wind, not even a small breeze, allowing you to smell it when your are in the right place [in the vapor plume]. One way to locate such a leak would be a hydrocarbon "sniffer" detector [calibrated for gasoline], but they are very expensive for an individual to buy for just one use. Good luck.j3h. There are multiple reasons that could cause this on earlier S80's, however one of the main reasons speaking with a local Volvo technician is for the return feed on the fuel pump (from the fuel filter) located at the top rear of the tank on the passenger side of the vehicle to hairline fracture. The symptoms will likely be -

harder to start from cold

a strong smell of gas on exit from the vehicle

slight smell of gas while driving. If the issue gets worse, you will find if you park the vehicle on an uneven surface where the drivers side (on LHD) is more elevated than the passenger side, the gas will drip to the ground from the underside of the tank just in front of the rear passenger wheel (Don't inspect this while smoking or with a naked flame for all the obvious reasons). What is happening is the pipe has hairline fractured and is spraying fuel over the underside of the service hatch (access under rear seat) and then collects in the fuel pump access well / fuel pump housing, this happens as soon as you turn the ignition on and pressurize the fuel pump. If you park on slope, the fuel then drains from it's collection point above, via the side of the fuel tank to the ground below. The fuel leak upon stopping the vehicle and turning of the ignition (and hence the fuel pump) appears to cease once enough fuel has leaked out to normalize the pressure in the fuel return line from the Fuel Filter back to the tank. The repair was quoted by Volvo Dealership at 2.5 hours for In Warranty and 4 hours Out of Warranty - not sure why there is a difference. Vovlo - Jump on the discussion board anytime and enlighten us consumers please. The Pump itself is approx $250 for an aftermarket on the web or just over $300 from the dealer for OEM part. You also need 2 OEM rubber O ring gaskets approx 5" in diameter which are about $4 each. For those planning on undertaking this as DIY "be aware", you will need the special Volvo tool to release the securing ring around the Fuel pump which is like a 20 slot 4.75" Dia. pipe with a socket hole on the top (Tool from Volvo is approx $100). You also need to consider the accurate alignment of the pump and sender as it is dual float design and if mis-aligned wont register right on the gauge and may impact other systems like DTE etc. Also note, there are two hatches one ether side of the tank - the one on the driver side is the Sender unit and is attached via wires inside the tank to the fuel pump, both hatches need to be opened to do this job hence the 2 gaskets and the wires need to be disconnected from sender prior to pump removal - careful with sender unit as it wont take much to damage it, and remember before removing pump or sender to clear all dirt / debris before it falls into tank as parts are removed. Wires from new pump then need to be fed back through tank and connected to sender unit. Torque on the holding rings is approx 50 lb/ft according to Volvo tech so don't expect them to come off by hand and you need to torque them down right, or again you will run the risk of gas fumes / leak which is what you are trying to resolve ! I may be inadvertantly missing some details here, but hope this helps all of you with issues to identify if this is your problem and help prepare you for the dealership discussion or potential DIY repair, however this is only documented here as background information and is no substitute for professional help / opinion from a qualified technician, and as such, I assume no liability for any type of damages as a result of what is posted here or anything you may choose, or choose not to do based on this post and it's details.

I also specifically assume no liabilty for loss of Volvo sales as a result of this post. I did not create the problem and I am only documenting what I have found to date about the problem. In closing -

A gas leak is a highly serious issue and needs to be addressed ASAP.

If you go the DIY route, you MUST disconnect the battery prior to commencing any work, DO NOT SMOKE !!!!, ensure tank is drained or has as little gas as is practically possible (there is about 3/4 of a gallon left by my calculation when the DTE indicator goes from 15 Miles to ---- in my S80)

Have a suitable fire extinguisher close by and consider having someone else close by you during any stage of the repair that has exposure to gas / fumes.