Tachometer not working
 

Hi all. I know there’s a lot written about this but I don’t see exactly what I need to know.
1985.1 car with the engine replaced with the same early type.
Since engine replacement the tachometer doesn’t work.
The mpg gauge does, the lights around that gauge do.
I’ve taken the instrument cluster out and removed the tachometer and cleaned it all up already.
So it seems the signal isn’t getting through or the tachometer itself is broken. (The needle moves slightly with the gauge in my hand so it isn’t frozen).
Any thoughts on how to trace the problem? Thanks.

Likely that you didn't reconnect the fitting from the engine wiring harness to the dashboard's wiring harness.

There is a red connector near the DME computer that needs to be connected to send a signal to the tach...

[QUOTE=kdjones2000;10456401]Likely that you didn't reconnect the fitting from the engine wiring harness to the dashboard's wiring harness.

There is a red connector near the DME computer that needs to be connected to send a signal to the tach...[/QUOTE



Thanks. The only red connector I see is looking through the dash, the brown wire looks like it comes from the tachometer plug and joins to the red wire on a connector which then looks like it earths to the metal frame. Is this the red connector you refer to?
Or please let me know where the connector is I’m looking for.
Other than a birds nest of wires I don’t see another red connector.
Couldn’t upload a photo from my phone. Will try tomorrow.
Thanks.

Look at the cable coming out of your DME. There should be a connector that attaches to your interior wiring loom. On the 924S in '87 it is a red connector.

You said you did an engine swap; you may have missed plugging this in when putting things back together.

The wiring from the ecu to the dash is definitely not as it was from the factory. The only red connector I see goes to an earth point. I also see a thin black cable coming off the end of outside of the metal ecu box from a screw connection which has been cutoff. The guy who installed the engine tells me he didn’t disconnect anything under the dash with the motor change so I wonder if there is a connection in the motor or from the crank which send a signal to the ecu for revs which was not connected? If so where would the engine connection or sensor be?

See this blade-like connector? This is on an late wiring harness.

https://i.postimg.cc/Bnhxpg3X/IMG-20...-071023249.jpg

The early cars have a rectangular connector in this same location, very close to the DME connector. This connector needs to match up to whatever is on your interior wiring harness.

Ok so I need to take a break from this as I’m away for a couple of weeks.
I definitely don’t see a red connector other than a small wire to wire connection in a rubber sleeve which seems to end in an earth point.
Looking inside the dme plug if I have read other posts correctly it is pin receiver 21 which is the tacho
Pin. This actually looks like the pin receiver hole is empty, other holes have a metal connector inside but not this one. Is this right?

The plug image shows the receiver place for pin 21 looks empty.

The second photo shows the plug in place and the red connector near the dme which looks like it terminates to an earth point.

Well the FRWilk site is no longer, so I guess this information is no longer out there:

https://i.postimg.cc/CMq6CwhW/Early-Late-DME-1.jpg

https://i.postimg.cc/sx7634HV/Early-Late-DME-2.jpg

After disassembly and assembly a couple of times the tacho worked fine, but no idea really why.
However, after making an adjustment to idle speed (it was a bit fast) now the tacho shows a good idle is running only 400rpm and revving flat out is only 1000rpm.
Any ideas why my tacho has decided to run low all of a sudden?
Thanks.

we just got our 84 back on the road. the tach had been working, but we had several elec issues in the fuse panels.

now the tach sits above 6k and does not move.

seems we fix one elec issue and create another.

sure some elec issue but surprised the tach sits a the top and not a zero.

what is weird is the tach sits at zero until you try to start the car. seems as soon as power hits the DME it jumps to over 6.

thought if the wire got pulled loose somewhere it just would not move....

thoughts?

sure wish the tach was working....

when we first drove the car it would cut out at higher rpm. now that we have gotten to drive a couple times it is clear there is some ignition issue.

since the tach is not working cant be sure of rpm, but do not think I am hitting the rev limiter.

runs smooth and pulls good right up to the point it starts bucking. clearly it is a high rpm issue. going to try another used coil I have in my spares box. will report back.

suggestions on what to check for such a condition?

thanks.