Engine speed, Pin 9, rerouted, still no tachnometer?

[lolcantturn]

So my M20 harness i'm modifying to be an M50 one is from a 1986 ETA, I don't know how to get the tach to work but everything else I followed and my car starts up and works fine but the tach don't work

http://www.akgmotorsport.com/usm50swappins.php

I followed this pinout chart, I don't have a pin NINE that I can connect to pin 20 on the M50 (which is engine speed), and I don't understand how I can get the C104 speed output from the glovebox. Any thoughts?

[Wh33lhop]

You need to run a wire from the tach signal in the m50 harness to the c104. Pretty simple.

[lolcantturn]

Any pictures of how it's done? I still want to retain a stock C101 look without any extra wires coming in and out of it.

[e30rapidic]

you can attach these wires directly from the ecu plug

wire that goes to pin 24 on the x20 goes to the red/yellow wire of the c104
wire that goes to pin 14 on the x20 goes to the black wire of the c104
wire that goes to pin 20 of the x20 goes to the wire on the back of the instrument cluster in the circuit board with the green covering that snaps onto the cluster.

[lolcantturn]

eek, that sounds like its going to look really ugly with a bunch of wires coming out of the x20 in random locations.

[e30rapidic]

eek, that sounds like its going to look really ugly with a bunch of wires coming out of the x20 in random locations.

that's why you figure out which ecu pin they come from and make a connection from that end. That's how I did it.

[lolcantturn]

I'm about to just get a later model M20 harness and redo everything haha. Mind sharing which pin it was on the ECU?

[jeswaw]

Just run a wire out of the harness over to the tack. Either under the glove box or under the knee kick panel, either or will work and it wont mess with your connector. Thats what I did in both of my 24v cars.

[MattM]

you can run the wires in with the rest through the firewall, then behind the radio over to the C104.....

I cut the other end of the C104 off the M20 engine harness and spliced the wires all in so it still plugs in.

getting the first wire through the fusebox and out with the rest is somewhat tricky... once done you can use it to pull however many wires you want through.

[lolcantturn]

can you show me a picture of how you did it? That way I can get a clue of how to do it.

[MattM]

i dont have a picture of it... nor do i want to pull my dash apart to take one...lol

[lolcantturn]

OK WELL,

I got awesome help from Davesmed (awesome awesome dude) and he pinned my Pin 9 to pin 20, and I still have no engine speed! Do I have to have the fuel rate connector connected to? Since, don't they run off the same fuse? Quite confused, Thanks guys

[DaveSmed]

Nah the fuel rate doesn't need to be connected.

First thing is to check continuity from the DME to that wire, then make sure there is a coding plug in the dash of some sort. Who knows it could have gone with the M42.


Somethings been bugging me. Check and see what fuel pump is in there. That tank belongs in a dual pump car, so if it's the fuel pump that was originally in the tank, then you are definitely going to have fueling issues once it hits the road. The correct carrier for a high pressure in-tank pump will have the bullet style terminals, not the spade style.