1997 850 Fuel Pump Wire Seal

jpeisker · Post by **jpeisker** » 11 Nov 2009, 15:42

Trying to track down a fuel vapor leak on my '97 850. No liquid fuel can be seen but there is an occasional gasoline odor inside and outside the vehicle. Suspect it is at the top of the fuel pump because that is where the odor is strongest.

Poking around in there I don't see any cracked or suspicious rubber lines or elbows. But I do see two things that I'm curious about. The waxy seal around the fuel pump wires seems to be deteriorating and flaking out. Wondering what this seal is made of and if it can be the source of vapor leak. This is the area with a red arrow in the photo below.

There is also an unused white tube coming out of the pump body that looks like it should have a hose connected. This tube also seems to be decaying and maybe is cracked or perforated. Identified with green arrow in photo below.

: 850 Fuel Pump; Volvo 850 Fuel Pump.jpg (32.99 KiB) Viewed 3563 times

So my first question is can the pump wire seal be leaking (is this a known problem?) and, if so, what is the recommended method for re-sealing?

The second question is what is this white tube for (seems to be blanked off)?

Post by **misha** » 11 Nov 2009, 16:20

That gasoiline odor can be decieving....usually,the culprit for fuel odor is fuel pump assembly gasket.

About extra white tube....every car have it and it's not in use.It's factory sealed up.

I think,that wire seal on fuel pump assembly is there just to prevent short circuit between those two wires(+ & -).
My opinion is that is impossible to have a fuel leak or fuel odor in that place.

Like i said before...check fuel pump assembly gasket.

volvomileage · Post by **volvomileage** » 11 Nov 2009, 17:47

+1 on the rubber gasket make shure its seated properly......
step two make shure the black ring that secures the pump is well in its threads and tight...

step 2 follow the gas lines to the engine ....

cheers !

mapaed850 · Post by **mapaed850** » 11 Nov 2009, 18:14

Wasn't there a recall on the gas tanks in 850's? I thought the symptoms were seeping gas and fuel odor. The recall was mandatory in "hot weather" states and optional in the rest.
I'm not certain about the details but could this be the problem? I have a fuel smell in my car too but only when the tank is full.I recently replaced the fuel pump and seal. The gas odor was there before and after the repair though. I've been meaning to check out the recall but havn't got around to it yet.

volvomileage · Post by **volvomileage** » 11 Nov 2009, 19:13

double check.....some members here have reported a gas leak when they fill tank to the rim...double check the next time you fill up..

otherwise i would check the gas lines especialy those that are on top of tank for leaks...or the fuel line that goes on the fuel filter they can let go gradualy...

cheers....

jpeisker · Post by **jpeisker** » 13 Nov 2009, 10:06

Thanks for the input everybody. I had Volvo check out the fuel tank for leaks and mounting issues per their recall campaign a few years ago, so that should not be an issue.
The leak is definitely at the very top of the pump, determined by a handy little combustible leak detector. I can isolate the leak to a small area but it's very crowded around there with two hoses connecting to the pump, two other hoses running nearby (one with a hose clamp fitting), the fuel pump wires, and the nut and sealing gasket. Any one of these might have a crack or pinhole or deteriorating sealing material. The sensor finds no vapors around the fuel tank itself or along the other hoses as far as I can tell without lowering the tank.
I was hesitant to pull the pump housing out for fear of breaking the jar top nut or damaging the gasket (it's 12 years old now). So I ordered a special spanner tool for removing the big nut, along with a replacement gasket. While I'm waiting for these to arrive, I'll poke around on top of the pump housing this weekend to see if anything obvious shows up. Maybe I can make the sensor more discriminating by shoving some narrow tubing over the end of the probe. If so I should be able to pinpoint the leak down to a few millimeters.
I will report whatever turns up for the benefit of others who read these threads for similar problems. It may take a couple of weeks...
Jim

jpeisker · Post by **jpeisker** » 22 Nov 2009, 18:31

OK, so I have the fuel leak taken care of now; turns out there were three different issues.

Main problem was a cracked and leaking hose that runs between the fuel pump and the level sender:

: Overflow return hose crack.JPG (184.24 KiB) Viewed 3494 times

This bugger brings fuel from the filler overflow tube back to the top of the tank. Many others on this forum and elsewhere have had the same failure and it is most noticeable after filling up. The hose cannot be replaced without dropping the tank so I did the other work with the tank on the driveway which is easier than working from inside the car.

The replacement part is much longer than needed, but it is easy enough to cut to size:

: Replacement hose longer.JPG (242.28 KiB) Viewed 3494 times

Because both ends are different sizes I didn't want to fool around with parts store fixes so got the real Volvo part. It was relatively inexpensive ($15) but bulk fuel hose would have been cheaper if you could expand one end. In case anybody is interested, the large end tube measures 18.5mm (0.73") OD and the hose ID was 16mm (0.63") or so. The smaller end tube measured 12mm (0.47") OD and the hose was 10.5mm (0.41") ID. So I would bet that if you could find any fuel hose with a 5/8" or 3/4" opening on one end and 3/8" or 1/2" at the other it would work.

The second leak area seemed to be around the fuel level sender/sensor:

: Level sensor gasket leak.JPG (305.91 KiB) Viewed 3494 times

It was not wet and my combustible gas sensor did not go off in that location but the fluid stain around the fitting suggested a leak at some point. Again, this gasket was cheap ($4) so I got a real Volvo part to replace it. I have a pair of very large slip-joint pliers (up to 5") and it worked well for loosening/tightening the big plastic nut around the level sender. It should also work well for the fuel pump nut when that became necessary.

The final area of concern was the waxy seal around the fuel pump wires:

: Fuel pump wire seal decomposing.JPG (301.82 KiB) Viewed 3494 times

On other forums people have commented about this failure and actually had liquid spitting out of the failed seal. My detector picked up vapors here, so I decided to carve out the superficial decomposing crud and then filled back in with QuikSteel Plastic Repair. This white epoxy sets up in about 4 minutes and is suitable for plastic fuel tanks.

After I took care of these three items I cleaned up the tank for grins and re-installed it:

: Repaired and all cleaned up.JPG (323.9 KiB) Viewed 3494 times

Will give it a couple of days to let all the fumes evaporate before re-filling the tank but I have fair confidence that this will take care of the leaks. I believe that these were also contributing to occasional evap leak codes.

Regarding that unused plastic tube on top of the fuel pump, it appears to be an option (regional?) for a heater in the fuel pump, according to an Alldata illustration which shows heater wires in this position. The thought of a heater in the fuel tank really scares me, but I still can't figure out how an electric motor (pump) inside an explosive environment is safe either.

Post by **misha** » 24 Nov 2009, 16:46

jpeisker wrote:...The thought of a heater in the fuel tank really scares me, but I still can't figure out how an electric motor (pump) inside an explosive environment is safe either.

Simple...there's no air in the tank.

Post by **cn90** » 27 Nov 2013, 10:32

jpeisker wrote:...The final area of concern was the waxy seal around the fuel pump wires...

Old post but worth mentioning "Butyl Rope", a material that feels like chewing gum and is used to attach windshield glass in older Chevy etc. from 1980s. Any autoglass shop should have this. It is about $10 for a roll. Butyl Rope is also used to seal "Vapor Barrier" inside the car door. It is soft, pliable, and very easy to work with.

It is petroleum product, so it will work fine to seal the leak that appears in the wiring area. Hint: if you see fuel in the wiring area, chances are the fuel leaks out of the wiring passages (through the white plastic top cover).

Use a small screwdriver to remove old wax, taking care NOT to damage the wiring.
The fill the space with Butyl Rope. This will seal the leak very nicely.

BEFORE:

: VolvoFuelLeakButylRope.JPG (103.78 KiB) Viewed 3146 times

AFTER:

: VolvoFuelLeakButylRope2.JPG (74.62 KiB) Viewed 3146 times

Post by **erikv11** » 27 Jul 2014, 15:19

I just did the fuel pump wire repair this afternoon, thanks for the great guide. I used Loctite Epoxy Weld to fill the cavity surrounding the fuel pump wires because
(a) I had some already and
(b) the manufacturer says it is gasoline resistant and
(c) a flowing liquid substance (i.e. unhardened epoxy) will be superior to filling nooks and crannies around the wires and sealing nice and tight around the entire inner edge surfaces of the cavity.

Took like 45 minutes to open things up, clean out the crumbling crud and evaporate any gasoline in the immediate area, and apply the epoxy. I filled it up level with the top of the cavity. Waiting for the epoxy to set up a couple more hours then I will go to the station and fill it up to the top. Hopefully this is the last of the tank-top fuel leaks on this car (95 R).

http://www.loctiteproducts.com/p/epxy_w ... mpound.htm