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74 Spider 78 Spider 84 Spider
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Discussion Starter · #1 ·
The car runs and all. but the Tach doesn't work. looking at my coil it's a mess of wires and one is real shady. 6 wires plus the high tension wire.

Positive wires:
green/black stripe goes along radiator to fuse #7.
black that appears to be the outer shielding on another black wire that leads to the FI computer? You can see this one exposed in a couple places. Why is there a wire inside another wire?

Negative wires
small white goes along the radiator to the Tach which does not work.
large white I think goes to the ignition computer terminal #1.
white/black stripe to the FI computer?
large black is inside the other black positive wire and appears to go to the FI harness?

I have the FI diagram but no wire colors shown so not 100% sure about the black wires and the white/black wire.

I assume they are all attached correctly but what concerns me is the two black wires that seem to become one and the exposed parts, but I don't think it's grounding out at the moment. But not sure how to cut and replace it since one is inside the other.
 

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Why is there a wire inside another wire?
The 'sense' wire for the drive relay is a white (or maybe yellow?) wire inside a shielding mesh and all inside a black out cover. It sends a tachymetric signal to the drive relay, the drive relay then powers on the fuel pumps. The shielding is to protect against stray signals.

...large black is inside the other black positive wire and appears to go to the FI harness?
I don't recognise that wire.



1644581
 

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But Mad North-Northwest
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Dear god, but some of that wiring is super sketchy. That one wire on the + terminal is all exposed, green, and corroded and really needs fixing. Also, are those the tach & ECU wires on coil positive? Pretty sure they should be on minus.

You should try to get Papajam's wiring diagram for an '84. I'll PM you the one I have for an '88 which might get you started, but if you ask around there should be a version available that's more specific to your car.
 

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74 Spider 78 Spider 84 Spider
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Discussion Starter · #6 ·
I have the Papajam 84 diagram. It shows the green/black on the + terminal and white on the - terminal for the Tach...which does not work.

Should there only be a single wire on the positive? only the green/black? all the rest on the negative side?

The "sense" wire is shielded? I have a shielded wire on the negative that the shielding branches off and is somehow attached to the positive.
 

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74 Spider 78 Spider 84 Spider
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Discussion Starter · #8 ·
I see on the 88 diagram the "shielded" wire goes from negative coil to the FI ECU #1....and the outer shielding wire is an earth ground.

If that's the same as on the 84...then I need to remove that shield from the positive coil and ground is to the chassis. But that inner wire is also black and not yellow...
 

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They change a couple of the wire colors on the 86 and up models. Wires still go the the same locations.
 

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The car runs and all. but the Tach doesn't

small white goes along the radiator to the Tach
...it goes along the radiator? Is that normal on early 80's spiders?

I'd test continuity of that thin white tach wire from coil negative to tach unit. If that is good then I guess the tach needs sending out for repair.
 

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These days, who is curating Papajam's wiring diagrams?
I have copies of his wire diagrams for Series 3 Spiders. And a few random older models.

Post a plea or start a 'conversation' (aka private message). Jim's work is copyrighted. He gave them freely to Alfa owners but always asked that they not be used for profit, sold or posted publicly. We're keeping that part of his legacy alive.
 

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74 Spider 78 Spider 84 Spider
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Discussion Starter · #13 ·
...it goes along the radiator? Is that normal on early 80's spiders?

I'd test continuity of that thin white tach wire from coil negative to tach unit. If that is good then I guess the tach needs sending out for repair.
the harness goes along the cross member in front of the radiator. Should I test for a voltage signal as well? The PO did have a lot of the interior/console/etc out not long ago. Several of the warning lights do not work. Things like the brake warning light come on with the key but then will fad out in a few seconds...has no correlation to the actual brake lever position or engine running or not...it's almost like the "check engine" light on a modern car that illuminates and then goes out when first turning the key to "on".
 
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