Hi,
I bought a set of clocks for my HCS engine with a tacho but cannot for the life of me get it to work!
It will do half readings fine (from 1 coil) but I cannot get both coils connected together working properly. If i use diodes from the two coil outputs so they don't interfere with each other, then i don't get any reading, probably because the switch of current from one coil to the other is instantaneous, so they are never both 'off'.
Somebody told me to use the flywheel sensor output, but isn't this just a position sensor and will send out too many as it goes round each notch in the flywheel?
Does anyone know therefore how I can 'double' one of the coil outputs to get a correct read, or create a gap between the current switching between coils, having them both connected to the tacho somehow?
Many thanks for any help or suggestions. James Stevenson, did you get your clocks working in the end? just asking as you've got a similar engine so might have had the same problem.
Regards
Mike Farrow
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Hi
I cant get my tacho to work but as above i was told to connect it to the flywheel position sensor (speed sensor)
i have the tech book for this engine and the position sensor outputs speed so try that,
mine is a 1 litre hcs if you get you'rs working let me know how and i will do it to my car
does you're car have a dis ignition system with a uesc module just to the right of the air filter
Kind Regards
James Stephenson
Fiesta MK3 popular plus owner/driver/cleaner/polisher/doctor.
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Hi James
cant get my tacho to work but as above i was told to connect it to the flywheel position sensor (speed sensor).
OK, the speed sensor thing doesn't work. I didn't think it would, as they are designed to output a very low signal several times per crank revolution, we only need a pulse TWICE a revolution. I can't think of anything on the engine which does that. I've thought about connecting 2 magnets to somewhere like the belt pulley and having a reed switch take pulses off twice a revolution. The only problem is how to stick the magnets on.
does you're car have a dis ignition system with a uesc module just to the right of the air filter?
yes it does have a dis ignition system. no the uesc module isn't just to the right of the air filter. Then again we are talking about two different engine bays.
Mike Farrow
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This is an aftermarket type tach?
Does it have a selector switch for number of cylinders on it? If so connect to one side of the DIS and select two cylinder engine.
Alternative is to rob the instrument panel from, say, an XR2. Knowing Ford it should fit straight in but dont quote me!
Andrew
Goodwood, aaaaahhh!
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Hi
i have got the clocks from an xr2 but i need to know where it connects to i mean where do ford connect it to
Kind regards
J Stephenson
James Stephenson
Fiesta MK3 popular plus owner/driver/cleaner/polisher/doctor.
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Hi James
According to Haynes manual, Ford connect the tachometer to the Earth side of the primary coil on the HCS engine, similar with the XR2. However the XR2 has 1 set of coils, so fires 2 cylinders per revolution. The HCS has 2 set of coils, which each fire 1 cylinder per revolution. Hence you get half readings when using XR2 tacho.
Andrew, not aftermarket unfortunately, so no switch :(.
I'm still working on it though, keep you posted
Mike Farrow
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Could be as simple as connecting a 0.5 to 1uf polyester ( Non electrolytic ) capacitor in series with a forward biased diode to each coil trigger and connecting the diodes together to feed the Tacho Regards Peter
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Hi
Thank\'s for the suggestion Peter. I would try it but I fear I might not have the right components.
In the mean-time however I\'ll try to be a pink fluffy dice by trying to re-construct the circuit diagram of the tachometer\'s electronics as best as possible. Hopefully there will be something obvious (like a resistor) when I draw it out on paper that looks like the amp-stage for driving the needle iron.
If I then half it\'s value with a new one I\'ll either be very happy or it will go bang :-)
I\'ll keep you posted.
Mike Farrow
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The Components are available from MAPLINS for less than a quid so do not waste your time. Come back if it does not work. Regards Peter.
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Hi
Finally got the thing to work (well, at the moment!)
I did what I said I was going to do 8 months ago and drew out the circuit diagram. Anyway, anyone who needs to do a conversion of a tachometer from single-coil to a wasted-spark ignition system (EDIS) on an escort of this mark (maybe fiesta, etc???) might want to read this.
Basically, there's a potentiometer on the circuit board of the tachometer (you can't miss it!). This is used for fine-tuning the needle so it reads the right rpm. If you follow the tracks from this potentiometer (two pins are joined together here so it acts as a variable resistor), you'll find that it is in parallel with a reisitor, a capacitor, and two pins of the IC. Make a note of the value of the resistor (mine was 146k). Unsolder this resistor and replace it with one of double its value (I used a series of resistors attached on a seperate board [to make 292k] and piggy-backed this to the tacho board). Anyhow, that seems to do the trick.
I still can't believe Ford charge an arm and a leg for a unit like this (I was quoted near £300 recently!!).
Mike Farrow
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