Mercedes W114 250 Coupe - help!

[grober]

Mikalor clips appear to offer a robust alternative to the ubiquitous "Jubilee"


Mikalor Hose Clips & Clamps W1, W2, W4 & W5

Mikalor

 

[Bellow]

Got the fuel rail back yesterday. The injectors needed to have the pintle caps from the old D Jet injectors put on so that they would fit tightly in the rubber grommets of the head.

John is not comfortable with using cable ties to secure the fuel rail - he thinks that at 3 bar of pressure the scope for the rail coming off is too high. I am going to think further about this, an alternative is using jubilee clips attached to the injector clamps - I'll take some more photos today to explain.

There is only the reaction force applied over the area exposed to fuel pressure.
Measure the diameter and calculate the area (in square inches) and multiply by 45psi (3bar) to arrive at the force value in lbs.

 

[Bellow]

Say the diameter is 1/2''. Then the force on each injector is 8.8lbs. Over the entire rail it is 53lbs.

A variety of metal ties here >> https://www.google.co.uk/search?q=m...hWKIcAKHczBB5wQ_AUIBygC#imgrc=rtp5LkJNEECE-M:

 

[grober]

Thought I would repost a couple of your piccies Charles to set the stage so to speak.

and

Not much room for manoeuvre there- maybe a couple of stout custom brackets/spacers?

 

[Druk]

John is not comfortable with using cable ties to secure the fuel rail - he thinks that at 3 bar of pressure the scope for the rail coming off is too high. I am going to think further about this, an alternative is using jubilee clips attached to the injector clamps - I'll take some more photos today to explain.

To my mind this hinges on whether the rail and injector pipe ends have a swelling of the metal that the rubber has to pass over with the clip t'other side. My experience of fabricated water cooling pipes without this swelling is that the rubber easily forces off; whereas with a swelling the clip doesn't even have to be tight for it to be quite secure. There's also the possibility of using the little crimped type clips and although they are semi-permanent they do look very neat.



.

 

[Charles Morgan]

Druk - do you have an image to share of that, my poor befuddled brain is having difficulty visualising it.

I got a coupe of poor images of the rail in situ. In essence the top of the injector is seated directly in the rail (held in by an o ring) and the nozzle directly into the cylinder head. In Grober's first pic above you can see the injector clamps which bolt directly into the head via the stud and are held on by a nut. This is extremely rigid. The original idea was somehow to use those clamps as the securing for the rail itself, and using jubilee clips or similar (two per clamp over the rail) you could really tighten in the rail on to the injectors and hold it in place.

Space is very tight - we are going to have to move the throttle bar linkage visible in the photo below about 1cm to create space for the return pipe.

 

[Druk]

Ah! I got the impression from what you said (and from Graeme's pic) that there was a short length of rubber fuel pipe between the rain and the injector.

Sorry.

I have the rail/injectors here from a 320 HFM and they have a spring clip securing the injectors to the rail. Can take a pic of that if it helps.

 

[grober]

MY fault perhaps I too had forgotten Charles injectors seated directly into the rail. I visualised 6 pipe stubs from the rail also [ no idea why]
Refresher course on the old system from back in January!
http://www.mbclub.co.uk/forums/2240382-post1990.html

 

[Charles Morgan]

The closer the rail to head the less chance of it moving around, it's a solid aluminium thing. If there was more room (and not a bugger of two surfaces with numerous important bits on) I'd have a bracket done.

 

[Druk]

MY fault perhaps I too had forgotten Charles injectors seated directly into the rail. I visualised 6 pipe stubs from the rail also [ no idea why]
Refresher course on the old system from back in January!
http://www.mbclub.co.uk/forums/2240382-post1990.html

Would this be a simpler way Charles? No alignment problems then.

 

[Charles Morgan]

No for a whole variety of reasons.

The rail is drilled and done, it is merely securing the rail to the clamps you see in that and the earlier photos.

 

[Bellow]

....

 

[Bellow]

Cable ties! Metal ones if the heat is a concern.
Even if the area exposed to fuel pressure is 1/2'' in diameter (Likely it is half that - 1/4 of the area, 1/4 of the force) then the force is only 9lbs shared by two cable ties. The tension in each strand is only 2.25lbs calculated on a generous 1/2'' diameter. Try breaking a proposed tie - they are strong.

 

[Charles Morgan]

I think I'll go metal ones then. They will blend in a bit better.

 

[Bellow]

Something along the line of these:

A bit of thought as to how to tighten and fasten them required (perhaps) but once on - neat and strong.

 

[Druk]

Space is very tight - we are going to have to move the throttle bar linkage visible in the photo below about 1cm to create space for the return pipe.

Would it not be expedient to fit a blanking plug to the end of the rail and drill and tap a new port in the top/bottom side to accept the return rather than have to shift the throttle linkage?

.

 

[John Jones Jr]

CM avoid cable ties, metal or otherwise. It's just not a good or correct solution, some would say it's bit of bodge. I'd spend a bit more time working out a way to use some original bolt holes along with a bracket/clamp.

 

[Druk]

Beat me to it JJ.

Excuse the poor art but here's a quick idea. Bit of flatbar (20 x 4mm) drilled and tapped and held under injector clamp nut. Shaped piece of flatbar over rail with screw down each side into flat piece to secure. If clamping pressure too much then screwed rod up from flat piece and nut top and bottom of clamp. All x 3.

Would both secure and locate rail. I could even be persuaded to manufacture if needed. At a huge cost of course.

 

[John Jones Jr]

Yeah, something like that. The simpler the better.

 

[Bellow]

I'm going to use Druk's drawing to suggest an improvement to address the one concern I have with cable ties.
The wrap of a tie around the MB bracket isn't ideal as it is contoured and will put a twist on a tie.
Instead, where Druk has a plate below the threaded boss, bolt (single bolt) a small rectangular plate (mild steel circa 3mm thick is ample) on top (not below) the MB bracket with the plates main axis running with the crank axis. It can be no longer than the space between the brackets and between the bracket (above) and the underside of the plates (3 of) the tie can go. (Think Druk's plate turned 90 deg viewed in plan and above the threaded boss, not below).
Fettle the plates with a file so no sharp edges are presented to the tie and notch if you want to restrict them from sliding.
The bolt (obviously) utilises the existing boss and can be tightened down hard as the first part of the assembly. Thus, it requires no locking nut or compound - which I suspect Druks bolts will.
If I haven't explained this very well (likely) I'll sketch it and post.