replacing hard fuel lines

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Robert Bondi
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replacing hard fuel lines

Post by Robert Bondi »

Anyone have any experience doing this? While scraping old crud off the steel fuel lines on the restoration car, I created a gas leak. Grr. I guess better to expose this hidden rust problem now rather than find it later on the road. This is a carb car with lower fuel pressure, so they might have already been leaking in an FI system.

Fortunately, the BMW feed and return lines exist and are on their way from Germany. They'll be lightly coiled, so the challenge will be in all the tube bending. I'm also buying a few different tool bending options. I've got one of those cross-bow style ratchet benders on the way and I'm also poking around on some smaller hand tools as well.

Big question is on the general strategy: Do I try to copy the old lines off the car or be under the car matching each bend to the contours of the underside? I also have yet to discover what secures these lines at the front of the car when they come up through the frame rail into the engine bay. I've done brake line bending, but those are all much shorter segments and on-the-workbench procedures.
Robert
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Re: replacing hard fuel lines

Post by dutch »

In the front ,the lines are just clamped to the side of the framerail right below where they go through the inner fender. I think you will find biggest challenge where they pass the rear subframe / diff. My 528 is all in pieces , but don`t know how I would fix that without dropping the frame...
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Robert Bondi
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Re: replacing hard fuel lines

Post by Robert Bondi »

No issue with access for me. The entire back end is all cleared out for restoration. Working on rust spots on the underside with everything removed is how this can of worms got opened...

dutch wrote: Fri Apr 19, 2024 3:08 am In the front ,the lines are just clamped to the side of the framerail right below where they go through the inner fender. I think you will find biggest challenge where they pass the rear subframe / diff. My 528 is all in pieces , but don`t know how I would fix that without dropping the frame...
Robert
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77 Euro 528
dutch
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Re: replacing hard fuel lines

Post by dutch »

ah, the good old reliable can of wurms... :shock:
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Robert Bondi
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Re: replacing hard fuel lines

Post by Robert Bondi »

Upon receiving the new fuel lines, the job looks a little bit easier than expected. I was expecting straight line just wound in a coil. Instead, it looks like BMW produces the exact line with all the bends in it. Either through storage or the shipping process, it gets gently wound up as shown. Therefore, the process really becomes identify which end is which, use the bending tools to carefully straigten the straight runs, and and use the bending tools to adjust all the bend locations, as needed.


New BMW hard fuel lines. A pair of return lines and a pair of feed lines.

Image


Beading on new fuel lines. On further inspection, the beading is actually right on the end inside the yellow caps. Might attention was initially focused on what I now understand is a stop for the hose end (shown) that is a feature not present on the originals.

Image


Variety of bending tools. It's basically guaranteed that no one tool will do all the bends.

Image
Robert
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Robert Bondi
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Re: replacing hard fuel lines

Post by Robert Bondi »

I finally got the new hard fuel lines installed after also cleaning up all the underside in the back end and mitigating all the rust spots with POR-15 and a top coat of flat grey. Only remaining spot is the weld repair panel to tackle in my other thread.


Cleaned nylon clamps and new holders. I also replaced those screws with stainless socket head cap screws (M4-0.7). The Phillips heads are terrible after years of rust. With 15 clamps between the tank and front frame rail, I was fortunate to only shear off one screw head and avoid a second headache by grinding flats into the screw head before removal.

Image

A new fuel hard line matched to the old. As mentioned, the job with the new BMW steel lines is really one of careful straightening and then tweaking the bends BMW already made. This made most of the benders unneeded, since most are better at bending straight tube. I found the bender with the single red handle at top of picture most useful for straightening and also careful use of a vice with 6" wide jaw.

Image

Cleaned up rear end with new fuel lines installed.

Image
Robert
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dutch
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Re: replacing hard fuel lines

Post by dutch »

That looks great.

the underside of your car looks way better than I expected too. Mine had very little damage at the carrier mounting points but the rest was a complete mess... :shock:
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Robert Bondi
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Re: replacing hard fuel lines

Post by Robert Bondi »

Thanks. Yeah, I've got some bad spots on this vehicle, but often somewhat localized; hence, the motivation if at all possible to keep my welding activity also confined. Plan is to practice with the new welder this weekend.
dutch wrote: Wed May 29, 2024 12:49 am That looks great.

the underside of your car looks way better than I expected too. Mine had very little damage at the carrier mounting points but the rest was a complete mess... :shock:
Robert
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maybeillbuyit
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Re: replacing hard fuel lines

Post by maybeillbuyit »

Very nice Robert. I partially replaced my rusted fuel lines at the back of the car and it was a lot of work bending and fitting the straight pipe up and around the rear subframe. When I remove the subframe ( when I do the suspension refresh) I was thinking about replacing the full lines all the way from the back to front. Having the prebent pipe would make it easier. Do you have the part NOs for those pipes? I'm not seeing those anywhere online

Any plans to reinforce the diff mount area? I know that can be a problem area on some cars
1977 530i another project
1979 635csi Euro "project"
1987 635csi
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Robert Bondi
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Re: replacing hard fuel lines

Post by Robert Bondi »

Sure. The hard fuel lines I found are up to 08/1979 and shared with E24. Here are the P/Ns

return, 16-12-1-115-338
feed, 16-12-1-115-337

No plans for extra reinforcement at the diff mount. I was pleasantly surprised to see nothing more than surface rust and actually see untouched primer inside the support structure. I also see no signs of stress and I'm not running any serious increases in torque or HP upstream, so just preventative clean up and a new mount.

Robert
maybeillbuyit wrote: Mon Jun 03, 2024 6:21 pm Very nice Robert. I partially replaced my rusted fuel lines at the back of the car and it was a lot of work bending and fitting the straight pipe up and around the rear subframe. When I remove the subframe ( when I do the suspension refresh) I was thinking about replacing the full lines all the way from the back to front. Having the prebent pipe would make it easier. Do you have the part NOs for those pipes? I'm not seeing those anywhere online

Any plans to reinforce the diff mount area? I know that can be a problem area on some cars
Robert
77 530i
77 Euro 528
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maybeillbuyit
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Re: replacing hard fuel lines

Post by maybeillbuyit »

Thx for the quick response. Those are the same part numbers I found on Realoem. I'm surprised they still sell prebent lines.

I have 2 e12 buddies who have found cracking/damage in the sheet metal in the diff mount area. They are having to reinforce. Both cars have no other mods and are just stock . I figured I'd reinforce that area when I have everything out.

Thx again. Dave
1977 530i another project
1979 635csi Euro "project"
1987 635csi
User avatar
Robert Bondi
Posts: 362
Joined: Sun Jan 11, 2009 12:33 am
Location: Austin, TX

Re: replacing hard fuel lines

Post by Robert Bondi »

Yeah, it's a common problem. There used to be a repair package or upgrade for it as I recall. I have two E12s and I see no degradation on either. One variable could be sheet metal thickness in that region. Both of my cars are 1977. Latest E12s were dropping weight everywhere. For example, years ago a replacement US bumper for 528i was 1/4" thick, while it was 3/8" thick on my 530i...looked identical otherwise.

Robert
maybeillbuyit wrote: Tue Jun 04, 2024 3:59 pm Thx for the quick response. Those are the same part numbers I found on Realoem. I'm surprised they still sell prebent lines.

I have 2 e12 buddies who have found cracking/damage in the sheet metal in the diff mount area. They are having to reinforce. Both cars have no other mods and are just stock . I figured I'd reinforce that area when I have everything out.

Thx again. Dave
Robert
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77 Euro 528
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Mike W.
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Re: replacing hard fuel lines

Post by Mike W. »

My suspicion, and I'm not at all positive, is that in '80 with all the changes, things got weaker. E28s with 3.3 and 3.5s did have more power and torque, but I also hear of many more problems with the E12 type diff mount on them.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
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