850 gas tank drop and fuel pump removal.

Post by **Red-Arrow** » 20 Apr 2011, 08:17

Hi Guys.

Well some of you know I had a gas leak from some place above the tank. When filling the tank up to the max without spilling fuel I would get a fuel smell and noticed the side if the tank getting wet with fuel.

OK so first we removed the rear bench seat and push into place the rear bench seat, this gives as access enough to unbolt the 5 nuts holding down the cover. We then unclip the 3 looms that feed the fuel pump, sender unit and pressure sensor? These looms must be disconnected before the bolts can be undone to drop the tank.

: fuel pump wiring looms.

The looms connect to the side of the car just under the passenger rear seats.

: Wire location

We then jack the car up and use an axle stand for safety.

First we open the fuel flap and undo the two torx screws which hold the filler neck in place.
Now we can unbolt the two metal tank straps that secure the tank to the under body. We do not undo the third bolt where the two straps meet. The tank straps are very flexible and will allow lots of movement to pull the tank down and back.

The tank will fall as soon as the last bolt comes out so. There is no danger of breaking the fuel connectors of hoses as there is lots of flex thankfully.

: Tank drop

I then used Dawn dish washing foam to test for leaks as all the hoses were in good physical condition which confused me.

I was not able to take a picture of this stage because I made a Royal frigging mess! I was not about to touch the camera with my oil foam stained hands! The important part for testing leaks is using the EVAP hose that connects to the roll over valve. I disconnected this pipe and connected it to a bicycle pump and slowly began to push air into the tank. In this picture the pump has already been removed so imagine its still in there.

: EVAP roll over valve

This is me trying to be clever

I realised I miss a few good pictures so I'm trying to show you what places to test for leaks.

I understand the heat shield can be a problem so check the mounts for them as well.

: Fuel pump and test areas

To remove the fuel hoses you simply lift the connector body up which some how allows the o-rings to slip off the barb. If you pull on the pipe you will end up breaking something. This is a simple part but I can see how somebody would make a mess of it.

: fuel pump ful hose connector

I discovered that none of my hoses leak but the fuel pump itself was the cause of the leak, it has a rubber seal with a lip that can be caught and folded if not seated correctly. I looked at the cars history and the fuel pump was replaced a few years ago. Who ever replace the electric motor did not seat the seal and as a result the car has been leaking gas for years.

The electric motor cannot be service, it is a 100% sealed unit I discovered. I really took it apart for the sake of curiosity.

This is a series of pictures that show the stages of deconstruction .

: pump1

: open shell

: black silicon sealant

: motor wiring

: spring and dampener

: filter screen; P1030746.JPG (210.22 KiB) Viewed 12922 times

Now I had to re-install the pump which is not hard but getting the tank back up in position was.

You can see that I applied synthetic oil in the screw because this shouldn't in theory evapourate and will provide an additional air seal. plus if I have to remove it again It will come off with less pain.

: synthetic oil in screw cap

I also applied some oil to the lip of the tank were the seal meats the rubber.

: tank cap end oiled

Then the pump gasket itself got some oil just for good measure. Its not enough to cause any problems in the tank.

: pump oiled

The hardest part was lifting the tank with my foot and left hand whilst trying to tighten the bolt with my right! I promise you it will piss you off dearly!

Not even Ju-jujitsu help me here, so after 30 minutes I gave up. I found a cylinder block laying around and used that directly under the tank to push it up as I lowered the car using the jack. This work perfectly! yes I was

and relieved

: Gas tank pushed up with cylinder block

: Tank strap crushed by block

I didn't fully take the car off the jack, I watched as the block made contact and slowly pushed against the tank until it stopped. The block also helped put the strap against the tank removing the slack from it. I was just not able to get the bolt in its nut using my hands and legs.

That is pretty much all there is. The pictures may make you think its a big job but its not really. It just takes time and preparation which I lacked on the day. I hope this helps any Volvo owner.

Good luck guys.

Post by **VCA** » 20 Apr 2011, 08:31

Very nice write-up. One note, you don't have to use synthetic oil to seal the o-ring to the pump and tank if you can't get any (or if it would be a waste to buy so much just for that). Volvo recommends plain petroleum jelly for this.

Post by **jblackburn** » 20 Apr 2011, 09:00

Excellent write-up! And not a fun job; I remember doing it years before. I smelled like gas for days afterward

I deem this repair database-worthy - and it's not your first either. Thanks!

Post by **kcodyjr** » 20 Apr 2011, 09:44

Why must the tank be dropped to service the fuel pump in an 850?

I've swapped several pumps right through that access panel in the photographs.

Post by **jblackburn** » 20 Apr 2011, 09:47

It doesn't; as I recall he had a leaky hose at the top of the tank somewhere.

Post by **Red-Arrow** » 21 Apr 2011, 20:25

kcodyjr wrote:Why must the tank be dropped to service the fuel pump in an 850?

I've swapped several pumps right through that access panel in the photographs.

I had a leak as Jack said, I didn't know the source of the leak and so dropping the tank was the only solution.

The fuel pump like I said cannot be service. It can be removed as you say from the rear cover without having to drop the tank.

Its been a few days since doing this job and the gas gauge is rock solid! with no smell of fuel. I should have replace the pump seal but I used some silicon but its probably not suitable for constant immersion ins gasoline. I will add use a true gasoline sealant.

Post by **Red-Arrow** » 24 Apr 2011, 04:09

Ah I knew I forgot something. The image if the folded fuel pump seal. This was the main reason for the fuel leak.

I have been monitoring the fuel consumption and now the car is doing around 140 miles for 6 gallons which is city and highway combined. 23.3 Mpg on average. I rest the trip computer and notice around 27 to 30mpg at 60 to 70mph

This is better than 19 city and 21 freeway. I know it seems silly but fuel turns into vapour and that will find a way out of your tank if its not 100% sealed.

: Folded fuel seal lip

kevinaussie · Post by **kevinaussie** » 23 Jun 2011, 19:10

I have a similar issue when I fill my tank all the way up.
I have a gas leak, I had the filler neck gasket replaced and it is still doing the same thing.

I have found this hose disconnected.
Does anyone know where it goes to?

Thanks
Kevin

Post by **Red-Arrow** » 24 Jun 2011, 19:31

That goes to the roll over valve it seems and its part of the EVAP system. you should have a check light on?

kevinaussie · Post by **kevinaussie** » 24 Jun 2011, 21:49

Do you think I will have to drop the gas tank to reconnect it?

Kevin