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Registered
1991 420 SEL
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172 Posts
Discussion Starter #1
Hello everyone

As has been mentioned a few times (thanks Wooky!) a fuel line refresh is in order, as some of these old W126s gain an added feature over time: being able to roast marshmellows :eek:

I'm starting at the back. I found threads that talked about replacing lines, or the filter, or pump(s), but not an overall redo.

I'm looking for some advice. My car has 70k miles on it.

So far, this is what I have planned, all either MB or OEM parts:

Neck gasket
Gas cap seal
Tank filter/screen
tank to damper/exit hose
return to tank hose
'filter to feed' line
Cap nuts
Check valves
rubber mounts
new banjo copper seals
Filter

I have a sending unit o-ring but think that's a job for a different day.

Iirc that's it so far. Is there anything else I should consider? What are your thoughts on the pumps - if they fail soon are they easy enough to change as a stand alone job, or should I bite the bullet and change them now? I do have some hesitation on startup.

Also I am experimenting with brass crimp ferrules and will comment on them later.

Thanks

Pete
 

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38 Posts
I looked at mine and thought the same. But I may have to go a different route. I'm more than like going to make my own lines and convert to AN fittings.

Socal
1984 MBZ W124
1989 BMW E24
1996 Nissan S14
2009 Audi R8
Honda Grom & Ruckus
LM7 4.8
 

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Premium Member
1999 500SL, 1988 SEC
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1,159 Posts
Make sure you get fuel injector line if you do your own. I purchased Cohline fuel line and ended up going back next year and getting gates fuel injector hose. I think there is one wonky line you have to buy. Its the one with all the fittings needing the copper seals. You should also get the 4 (?) rubber grommets (buffers in Mercedes speak) that hold the fuel pump on and offer isolation. Most times I have found those deteriorated. Watch out they use a lot of these on the cars and they are all different. I would also get the little rubber boot that covers the wire going into the fuel pump. None of these are expensive.
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,283 Posts
I believe the 'wonky line' that fellow member Stutz refers to may be, unfortunately, NLA at this point.

#119 in the image.

MBL
Screen Shot 2020-01-24 at 9.03.30 AM.png
 

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1991 420 SEL
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172 Posts
Discussion Starter #5
Sounds like good advice! I bought Gates Barricade 27335 for the underhood lines. I bought finished complete MB hoses for any hoses under the back except for the 'fuel pump to fuel pump' line #126-470-28-64 thinking the rubber bit is only a few inches long and I'll save $60 doing that one. I need to measure the OD of the hose though. I still may buy the finished hose.

The line with the copper seals - is that the one that is all metal, no rubber hose, 126-470-144-64? I was going to reuse it but change all the copper seals. The metal lines are in excellent condition.

A note on the factory new lines - I didn't want to buy them because they're silver! BUT nobody will see them under the back and it turns out I'm glad I did, as they have a protective sleeve over the actual rubber hose. I'll just have to learn to live with knowing that they don't match - oh the pain.

I did get the rubber mounts / isolators / buffers and will change them. Those seem like one of those kind of new parts that will vanish soon.

Can you give me more info on the little rubber boot? I can't find it.

Thanks.

Pete
 

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1991 420 SEL
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172 Posts
Discussion Starter #7
While I'm changing the gear oil in the diff this weekend I'm going to print that drawing, and pull the fuel pump cover to compare. I think I might be missing a part or two.

Should I change the fuel accumulator while I'm in there?

Pete
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,283 Posts
Thanks, I'm glad it showed light as it were.

As to accumulator, I wouldn't just change parts unless there is an issue really.

Here's another view of the fuel pump package from the factory manual.

M.

IMG_4378.JPG
 

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Premium Member
1999 500SL, 1988 SEC
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1,159 Posts
The little rubber boot is not shown but it covers the terminal on the electric pump where the wire attaches. I suppose its in the electrical section
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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4,085 Posts
The little rubber boot is not shown but it covers the terminal on the electric pump where the wire attaches. I suppose its in the electrical section
I know this one! 1239971681 $2.59 at mboemparts.com
 

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1991 420 SEL
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172 Posts
Discussion Starter #12
Gaa if I would've waited 5 minutes I could've added the grommets with no extra shipping!

But as it turns out they look fine. I did ask the supplier if they can add 2 of them to my order with no extra frt anyway.

I did get under the back of the car and pull the cover off the little surprise package of cost and goodness hanging under there :) and checked it all out.

I turns out I was overlooking a couple hoses, and my idea of reusing the one hose wasn't perfect - the hose under there is seriously heavy duty.

BUT THEN, it turns out I need to buy a meter of CRP 1234763026-5 for that little bit that goes between the copper wye fitting and the fuel pump, correct? So I could've clamped the other little bit that connects the two pumps and saved $50. Oh well, no big deal in the grand scheme of things, meaning, the grand scheme of how much I'm putting into this car! :eek:

That said, are there any other options for CRP 1234763026-5?

Also, the check valves have thick and thin copper washers - will it be obvious which goes where when I pull the old ones?

Man after seeing the fuel delivery bundle I'm so tempted to change everything at once. But see above money comment. And I don't want to be wasteful. I did see Pierre Hedary mention the 2nd gen accumulator can give hard cold start issues, and I do have a cold start issue, so I am going to change it. Otherwise I would leave it alone.

Thanks again

Pete
 

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1991 420 SEL
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172 Posts
Discussion Starter #14 (Edited)
Ordered the last bits today.

So, a parts list! For a 1991 420SEL

From the tank through the system to the line running to the front of the car:
:
2014700506 Mercedes Fuel Strainer - (it says this # on the box but the part says 2014700206 - seller checked and said it's right - hose below does screw in)
'Fuel tank to Damper cage' MB hose 126-470-16-75 (this goes from the strainer to the copper branch fitting ('elbow'), that goes to the 1st fuel pump and pressure regulator)

What I'm calling the copper branch fitting is officially the 'fuel tank elbow fitting 126-470-00-62. It is all metal and mine's fine so I'm reusing it.

Elbow (copper branch fitting) to fuel accumulator MB hose 126-470-40-75
Elbow (copper branch fitting) to 1st fuel pump hose 1234763026 CRP only (MB not avail) - this is a little piece of straight hose. But you have to buy a meter.
1st fuel pump to 2nd fuel pump MB hose 126-470-28-64
The 2nd fuel pump feeds into an all metal line (1264702764) that I decided to reuse (it's in great shape). This line goes to the fuel filter and fuel accumulator.
Hengst fuel filter 002-477-44-01
1264704275 Fuel filter to 'feed line' MB hose (goes to the front of the car / engine)

There is a hose that goes from the return line from the front of the car back into the tank as well, 'return line to fuel tank' MB 1264704175

I'm also changing the 2 ea check valves 1587010536 Bosch - these go on the end of both fuel pumps that connect to the metal line (1264704175)
And the rubber 'grommets' that hold the assembly to the car: 4 ea - Rubber Buffer MB 1269880011
I have also elected to change the fuel accumulator, Bosch 0438170055, you might reuse yours
I bought the nuts that go on the ends of the check valves/metal line above (1264704175) - I may not use them - they are MB # 1239900053
I bought a handful of the correct copper washers from Pelican -007603-012110-m131 just in case
I bought new rubber boots/ grommets for the wires to the fuel pumps, 2 ea MB 123-997-1681

And a comment - my hose clamps are in very nice shape so I can reuse them - they are not included in this list.
Also you will need a hose clamp for the 'return line to fuel tank' 1264704175

I managed to get the above for around $350 not including the accumulator. I got the accumulator off Ebay for $168 total.

As part of the rear fuel system I am changing my gas cap gasket (filler cap seal 140-471-00-79) and the seal around the filler neck near the cap, 'filler neck seal 1239973581'. these were about $20 total. I have a sending unit oring as well but have decided it's a job for another day. Until it isn't :)

I also bought an old 1-13/16" 3/4" drive socket to remove/install the fuel strainer. This works for a 46mm socket and completes my set of SAE 3/4" drive, otherwise I would've bought a 46mm. If you are going to buy one just for this job I found this: https://www.amazon.com/gp/product/B00BLPPK4O/ref=ox_sc_act_title_1?smid=AU1DM21810GBD&psc=1 on Amazon, a 'Bikemaster fork cap nut socket'. It might work better for you as it's very shallow and is 1/2" drive.

I have pretty much given up on the crimped ferrules for now.

I'll add some comments or possibly revise after I do the job, hopefully this weekend.

And hopefully this is correct!

Thanks everyone.

Pete
 

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Premium Member
1999 500SL, 1988 SEC
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1,159 Posts
You will have to cut the socket down for the strainer I think
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,283 Posts
Hey Pete,

That's a fine, detailed write-up on your parts list!

There are a couple of other items I'd make sure I could re-use or have on hand during reassembly.

Those would be the insulating spacers between the mounting bracket & the accumulator, fuel filter & the two fuel pumps, numbers 17, 23, 29 in the diagram.
They provide protection from dissimilar metals corrosion that otherwise might occur back there.

Just a thought.

M

Screen Shot 2020-01-28 at 1.53.40 PM.png
 

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MB 300SE '90, anthrazite grey, black leather
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186 Posts
My fuel filter rusted through after 60 000 km due to the missing insulation, so they are indeed important !
 

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Registered
1991 420 SEL
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172 Posts
Discussion Starter #19
Stutz thanks for the warning. I'm a tool junkie, so do I A) make the socket I bought work by hook, crook and/or grinding it down; B) Buy the other socket I linked to on Amazon; C) buy a metal bandsaw to cut down the socket I bought; or D) all of the above? The correct infinite money and space answer is of course D) :D

Thanks MBL and Seppo for that. I did notice them during my examination but didn't think twice about them, they look ok but belong on that list! In deference to my wallet (last seen curled up in a ball in the corner, copiously weeping) I'm going to roll the dice and hope they're good. If not I'll have to order them and wait till they get in.

Pete
 

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Premium Member
1999 500SL, 1988 SEC
Joined
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1,159 Posts
I simply took my grinder and cut a cheap harbor freights socket down by about 1/2. Pretty easy actually. If you don’t cut it, its a hassle and some sockets just won’t fit
 
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