?90 240 Bung nut help

Just replaced the sender unit on my ?90 240 and got a new bung nut with it. I can?t seem to get it back on again though. Removing the rusty old one with a screwdriver and hammer I think I?ve busted some of the bits on the fuel tank the bung nut locks into. When trying to hammer it down with the screwdriver I can only get one corner of it to get in place at a time while the others usually pop out. Does anyone have any experience with this or any tips? I don?t have the bung nut tool nor do I have the time to wait for one from IPD as I don?t feel comfortable driving around with an open fuel tank and want to get back on the road. If anyone has been able to come up with any other methods for this I?m all ears. Thanks

P.S. Hahaha.... bung nut

You are probably X-threading it.
The sending unit will have some sort of rubber seal that needs to be compressed by that bung nut.
I'd say, use some petroleum gelly to lube up the thread of the bung nut, then try to thread it on *while at the same time* applying some downward pressure on that bung nut. Once it has caught on the thread you should be able to screw it down all the way. But do NOT use a screw driver, that will concentrate to much force on a tiny area and will break plastic. Use a hammer against a squared wooden stick to spread the load as to limit the risk of damage to the bung nut.

You might have to bend the lead in edge down a little to help it get started, and yes use lube.

thro1264 said:

Just replaced the sender unit on my ?90 240 and got a new bung nut with it.

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New rings are usually crap, made of thinner metal that bends too easy, and not always quite the right size. Sometimes the new rubber seal is also a bit too thick, or a bit too hard, and won't compress enough to let the ring do its thing.

When trying to hammer it down with the screwdriver I can only get one corner of it to get in place at a time while the others usually pop out. Does anyone have any experience with this or any tips?

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Try to get all 4 started, if you can. Then a little tap here, a little tap on the other side, the other-other side, then the other-other-other side. Working around a bit at a time usually works better than just bashing one ear and hoping the ring spins. That just shifts it sideways, and *pop*.

If there's room without hitting pipes or wires, and if you have 2 big screwdrivers, you can sometimes cross them like a pair of scissors, and use that to pry the ring around, at least part way. Or a huge pair of pliers or channel-locks with a screwdriver through it to act as a turning handle. Better than nothing.

Janspeed said:

You are probably X-threading it.

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No "threads" on this one to cross.
It's a metal "lock ring" with ramps that go under rolled-over lips on the tank hole.

283SD said:

You might have to bend the lead in edge down a little to help it get started, and yes use lube.

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A touch of grease or anti-seize between the ring and sender should let it turn easier.

oops, i must have been thinking of a 740 or 940. my bad.

You should lube up not only the face of the bung nut but also the rubber seal / ring; I use a silicon product for this, not vaseline, but either would work.

Be patient, it's usually a PITA.

+1 on the two large screwdrivers crossed to allow downward pressure and twisting motion at the same time. It's the way I've done them until I bought the tool. I used large Craftsman from Sears screwdrivers because they had square shafts for better contact.

MasterBlaster said:

...Sometimes the new rubber seal is also a bit too thick, or a bit too hard, and won't compress enough to let the ring do its thing...

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This is what I envision is frustrating. I found the aftermarket O-ring seals to be harder than those I had in blue bags, but a recent order from a Volvo supplier was no better, as though Volvo turned to the aftermarket supplier.

As I don't have the tool either, it took me some time to combine the pressure needed evenly on the ring to compress the seal and get all four cams engaged under the tabs on the bung before being able to turn the ring. At the time, I figured if that final attempt didn't work, I'd pull the new seal off and put it back with the old, well-compressed seal.

Each time I do this I vow to build or get a bung tool, and each time I fail to follow through.

I would just order the tool, even with it you have to push down hard to get it on there. I use a good amount of silicone lube on the o ring, and press straight down with all my weight on it. It can still be a bit difficult but that will get it done.

If you use screwdrivers and hammers, I would say to get another person to help if you don't want to drive yourself crazy.

You must use a new o-ring every time you open the tank. I used a genuine Volvo seal and then opened the tank 2 weeks later to replace my rusty sender and ended up smashing the hell out of my finger trying to get the lock ring to seal using the bung nut tool. After removing the 2 week old seal I noticed similar to what Art mentioned that even the Volvo seal would swell after a short time exposed to the gas vapors. I had a spare seal that I threw in and it sealed easily, upon inspection of my young but used seal I found it had swollen quite a bit even with minimal exposure and compression.