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Author Topic: New engine wiring loom and a few small changes  (Read 2342 times)
Anders Dinsen
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« on: August 21, 2009, 10:15:39 pm »

For quite a while, I have wanted to replace or repair the engine wiring loom. I had several reasons: The green connector next to the ignition coil was suffering from overheating and a bad connection, I have installed a three circuit immobilizer circuit on "top" of the old loom and it was a bit "bulky", and the tape was falling off a few places on the old loom. So some time ago, I started fabricating a completely new wiring loom with the immobilizer circuitry integrated.

Working on the engine wiring is more or less impossible unless the induction is removed, so the carburettors had to come off the engine. While they were off, I replaced the plastic spacers between the manifold and carburettors with a different kind of spacer: A "MISAB Spacer". These are better in several ways and are generally recommended over the plastic ones, but the reason I chose to replace them, was the the plastic spacers did not seal perfectly in two places on the manifold, where the O-rings potrouded slightly over the edge of the manifold. This was between the two middle inlets. The MISAB spacers have cured this problem.

I also wanted to replace the cotton braided fuel hose I originally bought for the carburettors with fuel injection style hose. This was recommended to me by a friend, who told me that the cotton braided rubber hoses has a tendency to disintegrate when subjected to unleaded fuel  Shocked I was not aware of this, but on the other hand had noticed (both on the Weber's and on the original single Solex carburettor) a few black grains in the float chambers. These could only have come from the fuel hose.

Since this could quickly evolve into reliability problems (e.g. fuel lines in the carburettors becoming blocked), I decided to replace the fuel hoses with modern hoses. They don't have the nice look and feel of the cotton braided hoses, but what help are good looking fuel hoses, if they detoriate slowly? Wink

Here's a link to a series of photos showing the transplant:
http://gallery.dinsen.net/v/biler/Matra/technical/electrics/wiringloom/

And the finished result for the impatient:


I had only one problem with the new loom: The alternator didn't charge!

This confused me a bit, as I was quite sure I had it right. I was wrong: The problem turned out to be that this alternator needs more than the power supplied through the charging light to power the rotor coils while the alternator is starting: The other tab on the alternator should be connected to ignition!

Fortunately, I had fitted an extra inigion lead on the loom to drive the idle circuit fuel valve on the single Solex carburettor. This is not needed on the side draughts, so I just had to make an extension to that wire, and connect it to the alternator.

This is entirely my fault, as the feature is documented in Roy's diagram - though not clearly in the original wiring diagrams and alternator manual in the workshop manual. Fortunately, it was the only problem I had with the new loom, and I'm a bit proud of that! Wink

I still seem to have a remaining engine wiring problem: The water temperature never really rise above 80 degrees on the instrument, and the needle has a tendency to "dance" up and down when the car is shaking in idle. I'm quite convinced that this is due to a bad connection in the grey connector on the left side of the front compartment (next to the fuse board). I'll have to take a look, and replace it if necessary.

Current jetting, by the way, is:

Idle jets: 45F9
Main jets: 130
Emulsion tubes: F9
Air correctors: 200

The 200 airs are up from 180, and seems to be better. It now revs quite freely all the way up past 6000 rpm on the counter!  Grin

/Anders
« Last Edit: August 21, 2009, 10:24:29 pm by Anders Dinsen » Logged

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« Reply #1 on: February 24, 2013, 09:30:40 pm »

Hello
Where did you get your airfilter/innlettbox ?
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Anders Dinsen
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« Reply #2 on: March 05, 2013, 10:14:13 pm »

Hello
Where did you get your airfilter/innlettbox ?


The filter is the original filter. The airbox is custom made out of sheet steel and painted black. Nothing special there Smiley

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
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