https://www.e46fanatics.com/threads/e46-sulev-fuel-pump-repair-project.1311110/#post-19097061

 

I appreciate the link, but i'm thinking more along the lines of doing it without removing the tank

 

You may be on your own there then.
I don't have personal experience with this, but from what I've seen in my years here I don't know that there's a better way to go about it than the one that I posted above. Trying to do it without dropping the tank definitely seems to be creating a lot of work in order to save a little.

 

What's the problem with dropping the tank? It's not THAT hard to do, just a bit of work.

Fwiw, the rear subframe/suspension/drivetrain can all be lowered together as one unit once the driveshaft is disconnected.

Also, the two service ports under rear seat are small ... and what you are attempting does not need to be made any more difficult than it already is.

 

If you can cut the tank in just the right place and complete the pump motor replacement without having to remove the tank, that would be a lot easier.

 

It would be, but when it comes to cutting and welding stainless steel cutting it at the seam the way is done in the thread that I linked is going to be the easiest path.

 

It would be nice, but E46sulev (in post 6 of his writeup) states that it wouldn't be practical for replacing the filter/pressure regulator assembly ...

The size of the opening limits what you could do in the tank with it still in the car. It could probably work for removing/replacing the fuel pump motor, but definitely not the filter/pressure regulator assembly.

 

Running exhaust gasses into the empty tank is one way to neutralise petrol vapours and water is another way. The water just displaces the fumes from the inside of the tank but doesn't neutralise the vapours.
Also, when TiG welding it is best practice to have zero, or as little, a gap between the two parts being welded together. A 1mm gap from the sliting disc of a grinder isn't much of a problem for a well practiced welder but could prove troublesome for a DIYer.

As for how to do the replacement, I'd be going with the thread linked as there's a lot going on inside that SULEV tank to try and resolve through a small window.

Or, maybe using an aftermarket fuel pump hat or popping a Subaru, or other, basket in as these have the fuel pressure regulator built into the pump basket but filter is external. The sealing collar could be welded to the BMW tank.

 

You're going to have to drop the tank.

The reason there isn't much chatter is that almost all SULEVs end up in the scrapyards.
Where I steal their valve covers... muuuHhaahhaahaaHhaaahaaaaaaa.....

As to welding, purging the tank with inert gas is cheap, easy and foolproof. The old
way with water worked ok for brazing small holes, but it sucks a LOT of heat out of
the metal, and if you get too close to the water, the steam will contaminate the hell out of your weld.
You're not going to bridge a slitting disc cut with a TIG- it's even pretty hard with a MIG,
as you need 100% penetration to get a seal, but the tank's very thin.
Yes, stainless welds just fine with MIG, if you're set up to do it.

Me, I'd be replumbing the thing as a non- SULEV, but that's a huge job, too.

t

 

You're not going to bridge a slitting disc cut with a TIG- it's even pretty hard with a MIG,
as you need 100% penetration to get a seal, but the tank's very thin.

^^^
This.

The single best way to weld light gauge stainless is to do a TIG fusion weld, and an edge joint is the best way to do that. Which is why the factory did it that way and why the best way to attack getting into it again is to do the same.