98 V70 AWD leak on top of fuel tank

Post by **holler1** » 20 Jun 2013, 20:18

I have a leak on top of the fuel tank that only appears when the car is running, so I assume it is from one of the pressurized lines from the fuel pump. It appears to come from the top on the passenger side and runs down the outside and drips off the bottom of the tank. The car is starting a little slower than usual probably because the fuel pressure is bled off by the leak. I've not been able yet to see exactly where the leak is or which line it is.I have removed the two plates over the filter and the large tank on top of the axle (overflow tank?). I can't see any leak from there, but can see a little wetness on the tank itself. The filler pipe connection looks dry, and so do the pump cover and the lines going into the cover. I loosened the passenger side tank strap and lowered the tank a little, but still can't see far enough up on top to see the lines up there. I wasn't able to get the drivers side strap loose yet - very rusty and the socket stripped the bolt head. Tomorrow I'm going to try a borescope to see if that helps. I found a diagram of the tank that someone uploaded from Vadis, but it doesn't show how the lines run from the pump to the filter and back up front to/from the engine. If someone could tell me the exact routing of the lines around the tank and the fuel filter, and if I can isolate the leak to one or two lines, I think I might be able to snake out and replace the pressurized lines without removing the tank. The line going into the pump on the outboard side looks rusty, so I probably want to replace that line in any case. The pump itself has never been a problem.

My simplistic guess is that the outboard pressurized fuel line from the pump goes to the filter, then the line from the filter goes back across the tank to the front. However, I don't know if the line from the pump goes in the front or backside of the filter. I also would guess that the fuel return line from the engine goes across the tank to the drivers side where the sender unit is. I think there is another fuel line running from the inboard side of the pump across to the sender unit, but I don't understand its function. I read on one of the forums that the drivers side unit also is part of the pump. I really don't understand how the units on both sides function together

I have read several posts on replacing the fuel pump on the AWDs, but none of them address leaks on top of the tank. Obviously I would like to avoid removing the tank if at all possible. I'm pretty sure I can figure out how to remove line connectors at the pump and the filter. I may do the "hole cut" if I need to remove or pull up the pump to get at the connectors on that end. I read one post that suggested there might be some other "view ports" on top of the tank, but the floor above the tank seems solid to me except for 3 very small round metal inserts, maybe 2" diameter or so, underneath the seat. I took one of them out but the tank was right up against it.

Thanks for any good info, diagrams or suggestions. The car is my "backup" right now, so the fix isn't urgent, but I would like to get it going again.

Post by **Ozark Lee** » 20 Jun 2013, 21:01

You really only have two choices. Remove the entire rear axle and suspension to drop the tank or do the floorboard hole cut. My only concern on the latter choice is the sparks from cutting through the floor and raw gasoline. Does it only leak when the car is running or does it drip out even when the car is parked and has a fairly full tank?

It could be the seal beneath the big plastic nut that retains the fuel pump if fuel drips out even with the car off. That is, of course, an easy fix - once you get to it.

...Lee

Post by **jimmy57** » 20 Jun 2013, 21:07

Take out the forward load floor and then remove the round cover. That is where the fuel filter is located and it may let you see the source.

Post by **abscate** » 21 Jun 2013, 04:01

Could you open the port and then look inside with a fiberscope?

Nibbling the hole is probably safer than cutting with a blade if there is gas around. Have a fire extinguisher and an asst. on hand regardless.

Post by **holler1** » 21 Jun 2013, 06:50

jimmy57 wrote:Take out the forward load floor and then remove the round cover. That is where the fuel filter is located and it may let you see the source.

jimmy57,
I already opened the filter cover and the other cover underneath the wiring harness. I could only see a small wet spot on the small part of the tank that I could see from that angle. There is no leak at front or back of the filter. I know you've done some of these kinds of repairs; any other thoughts?

abscale,
I'm going to try the borescope today and see if I can get the tank a little lower. As mentioned, there doesn't appear to be any leak around the pump cover and connections. I want to find where the leak is before deciding to do any cutting. I'm pretty sure the leak is from some of the pipes or connectors right on top of the tank. Removing the pump top would be a secondary fix, and only because the pipe coming out looks a little rusty.

Ozark Lee,
It only leaks when the fuel pump is on, dribbles down fairly fast. It dries up with the engine off, even though the tank is almost full. I want to find the source before cutting anything (and drain the tank of course). I can get access to the pump top if I need to, but I can see it well enough to see that it isn't leaking from there (or the sender unit). I'm very intimidated by the idea of removing all the suspension. If I could only get access enough to see the top of the tank, there might be some way to fix it w/o removal of tank. I considered cutting the floor on top of the tank, but I don't see how it is possible, since the tank sits right up against it and that is where the leak is. (Maybe I'm dreaming, and the only way is to remove the suspension - that just seems like a humongous job).

Thanks for the replies. I still need a good diagram or description of the piping on top of the tank. Do you guys agree with my reasoning that the source is a pressurized pipe from the pump or upstream or downstream of the filter, or is there somewhere else there is fuel under pressure? I've been assuming the outboard line from the pump is the pressurized line, and the crossover line between the sender unit (drivers side) and the pump is some kind of return line. Is that right?

Post by **jimmy57** » 21 Jun 2013, 10:21

There is one high pressure, the one from RH sender out to line to front of car. There are two low pressure, the one from FPR to LH sender to feed the ejector pump and the other is the line out from ejector from LH sender over top of tank to RH sender. The last line effectively has no pressure.

Post by **holler1** » 21 Jun 2013, 11:45

jimmy57 wrote:There is one high pressure, the one from RH sender out to line to front of car. There are two low pressure, the one from FPR to LH sender to feed the ejector pump and the other is the line out from ejector from LH sender over top of tank to RH sender. The last line effectively has no pressure.

Thanks, this should help. I tried my borescope but it doesn't work very well and I couldn't see anything new. Still working on draining the tank. I disconnected the fuel line at passengers side of fuel rail and connected a hose to that but got very little flow when I turned the key to run. I also tried getting a hose into the tank thru the filler pipe but couldn't get it in far enough to siphon.

I found the following old post (jimmy57). I'm going to see if i can lower the tank a few more inches by removing the trailing arms on both sides and the VC if needed. Couple of questions. Do all the trailing arm bolts have to be removed, or just the front ones? I think probably all, will try it and see. Re: the bolt holding up the VC housing front. I don't see how to mark the flange; it looks like it only goes in one position. Re: the back bolts on the VC housing- are there only two at the bottom? I understand how to mark the propshaft and back VC connnection to diff. In your judgement, how much can I drop the gas tank with disconnecting the wiring and the filler pipe? I would like to leave the wiring in place if possible so as to run the pump to look for leaks after partially dropping the tank, if possible. Thanks for this old post- very useful.

by jimmy57 » Sun Sep 18, 2011 1:15 am
You do not need to drop the whole suspension. IT is still a lot of work but less so that dropping the whole thing.
Remove the rear side load floor pieces. flip up the forward load floor section and pull the carpet back at left and right sides to reveal the two 10mm head bolts that hold the forward floor in place. Remove the forward floor. remove the nuts holding the access cover and the cover. Undo tape around the rubber pass through pieces and unplug the white wires from the docked connectors taking note of which white wires plug into which connector. Undo the grey connector with the red and black wires. push those wires down under car thru opening. (If you want to pressurize system and look for leaks, delay all this until later, it does not have to be done now and if you find the leak and the repair doesn't require full tank removal, this may not need to be done).
Remove the trailing arms with forward brackets on both sides. The forward bracket for these blocks tanks from dropping and they are still in the was and only two bolts hold these to the control arm and they do not affect alignment.
Disconnect driveshaft at rear, mark it to the flange just in case it has balancing bolts. If the bolts are different lengths as noted by them sticking through flange on back side different amounts then you will need to keep bolts in order.
remove the bolt holding VC hosusing up. Remove nut from the flange and then mark the flange to the VC shaft so it can go back where found. Remove the housing and then mark and remove VC from rear end flange. Again this needs to go back where found. On Gen 1 AWD's these pieces are indexed for least lateral and radial throw and bolted up to achieve least runout.
Back where you found it on the rotating stuff is the rule.
If you have to take the tank completely out you will have to undo the filler hose and vent hose clamps and get those hoses off just outboard and forward of the fuel filter on right side top of suspension frame.
Siphon tank to make your tank lighter.
Remove the exhaust pipe that goes from aft cat con pipe to the muffler inlet pipe over left top suspension frame (actually do this before driveshaft and VC housing stuff).
Remove the plastic shields on front of each tank side.
Remove the 12mm bolts holding tank straps but beware tank now drops but you want it lower a bit for line removal and not drop. Use jack stands or something else suitable to support tank until the lines and wires are freed.
If you can find and repair the leak now you may not need to do the following things needed for full tank removal. Now would be the time to turn on key and let pump cycle to build pressure to find leaks.
The outboard lines on both sender caps will need to be removed. It takes a 90 degree V or C shaped tool to pull up on the black plastic cuff that opens the line retainers so they slide off. The inboard lines connector the two sender assemblies together and do not need to be removed for tank removal.
The wires to pump and gauge sender on pass. side and for gauge sender on driver's side will have to located and made free from anything they will hang on.
Now tank can be lowered more and the vent lines on top disconnected for complete removal.

djohnk · Post by **djohnk** » 21 Jun 2013, 20:59

It could be the seal beneath the big plastic nut that retains the fuel pump if fuel drips out even with the car off. That is, of course, an easy fix - once you get to it.

That's what I was thinking, or something in that general area anyway. I was just there installing a new fuel pump cartridge last week. I went ahead and cut a hole, wasn't too hard.

Post by **holler1** » 22 Jun 2013, 20:23

I got the tank lowered a couple of inches, and was able to spot a small spray on the top of the tank when I started up the car. It was hard to see in there, but the spray appeared to be coming from a rusty section of the high pressure line from the pump to the filter. In order to get it out, I needed to unhook it at the pump, so I cut an access hole with a drill and small hacksaw. The metal was easy to cut and I was worried about sparks from a grinder wheel. Anyway, I got it disconnected and pulled the line out. The line was weak at the rusty spot and broke when I tried to pull it out from the filter side. I got part of the line out from the filter side and the rest from the side of the tank. So I'm 90% sure this is it. The line is mostly steel with a couple of flexible sections at each end to the filter and pump connectors.

Question- should I try to duplicate the original line, or just go with a flexible line all the way? I'm going to look for some steel pipe; not sure I can find it.

Post by **holler1** » 23 Jun 2013, 18:57

After a lot of searching for a Volvo factory made high pressure fuel line from the pump to the filter of the 98 V70 AWD, to fix the leak described above, I finally found one at jimellisvolvoparts, part number 9161125. In case someone else runs into this problem, here's a picture of the old fuel line, broken at the rusty spot. The foreground end fits the filter, and has a valve attached. I twisted that section around a little trying to see how it was put together. The end in back is the quick-connect for the pump. The middle part of the line goes right around the top of the tank, and is the line nearest to the outer edge of the tank (passenger's side). I ordered the line rather than build it. I don't think there is room above the tank for a larger diameter rubber connector in the middle of the line. I'm a little worried about getting the line through the tight space above the tank, but will give it a try when I get the new line.

I put in a new filter and it went in without a problem. There is a small sensor just under the plate that is under the electrical connectors. I'm not sure what the sensor is (map sensor?), but the mount it was on was rusted and got broken off when I was disconnecting the line to the filter. I plan to try to re-attach it with a ziptie. I hope it is not sensitive to orientation.