stargoaly
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| posted on 10/9/14 at 07:49 PM |
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Sierra Tacho
Anybody out there help?
Have been building this thing for 10 years (Busy job). First build as well. Finally started it and it runs like a dream. Now preparing for IVA.
However I have a small problem knowing how to get the tacho working. I have a 2 litre silver top mondeo running of an early non PATS ECU. Everything
else on the car has been taken from a donor Sierra including the instrument cluster. On the sierra the feed to the tacho came from -ve on the coil
however there is no such connection on the Mondeo engine wiring loom (I did connect to tacho output from ECU with no joy) so I was going to splice the
feed to the tacho onto one of the output wires from the coil pack to the ECU and see if that worked. Has anybody ever tried this and did it work.
Any advice will be gratefully received.
Thanks
Dave
virgin builder
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avagolen
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| posted on 11/9/14 at 07:17 PM |
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Hi Dave,
I do not know exactly the signal requirements
but maybe it can be sorted with a few checks.
Do you have a volt meter?
If you run the engine and check the signal from the ecu.
If you connect the meter between ground and the signal and you
get a voltage greater than zero or if you connect it between
12V and the signal and get a voltage, this information can help
solve your problem. Please ensure you get your voltmeter
the correct way around....
I am away from internet most of the time. I will respond
when I can
Post your results here. If neither gives a voltage it may need a
resistor to + or - for an opencollector cct.
The Answer for everything, but never the last word....
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big_wasa
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| posted on 11/9/14 at 09:16 PM |
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The signal from the oem ecu works with the after market tacho but I've never tried with the sierra dash.
If you just hook on to the coil pack on the zetec, being wasted spark the rpm will be half that of a points system or the ecu output.
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whitestu
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| posted on 12/9/14 at 07:02 AM |
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quote:
The signal from the oem ecu works with the after market tacho but I've never tried with the sierra dash.
If you just hook on to the coil pack on the zetec, being wasted spark the rpm will be half that of a points system or the ecu output.
If it works at half rpm from one of the coil pack feeds it may be possible to connect the tacho to both feeds with a couple of Zener diodes to get a
full reading.
Does the tacho definitely work?
Stu
[Edited on 12/9/14 by whitestu]
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stargoaly
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| posted on 14/9/14 at 09:14 PM |
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Thanks to every one for their replies. Wife got me decorating all weekend when there are more important things to do.
Stu, Tacho worked when I removed it from the donor car, however I do have another I can try.
I'm going to try the things suggested this week sometime. Again thanks for your thoughts.
Dave
virgin builder
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Non custom
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| posted on 26/9/14 at 07:12 PM |
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This is the diode mod done on cosworths to solve the same issue when using wasted spark setup on them may help I don't know ??
http://www.autosportlabs.net/images/1/13/Tach_circuit.jpg
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stargoaly
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| posted on 27/9/14 at 06:41 PM |
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Thanks to you all for your help.
I have ended up splicing into one of the outputs from the coil pack to the ECU and my tacho now works although it is reading half what it should do so
as said earlier next stage is to splice into other and use the circuit Non Custom sent.
Many thanks again
Dave
virgin builder
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Non custom
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| posted on 28/9/14 at 09:22 PM |
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I beleive that mod is done at the back of the clocks for ease also stargoaly 
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