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Guest Message by DevFuse

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Where to get engine speed signal (1992 Legacy EJ22)

LPG engine speed ej22

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5 replies to this topic

#1 stickedy


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Posted 19 January 2014 - 10:26 AM



I'm currently converting my 1992 Legacy EJ22 to LPG and I have a problem to get an engine speed signal. the wiring diagram for the LPG control unit tells me to connect the corresponding wire to ignition coil minus or to another signal with min. 4 Vpp (peakt-to-peak voltage). Since there's no minus at the ignition coil, I took the minus at the igniter. But I don't get a proper signal there.


Has anyone an idea, where to connect that wire? Thanks!

#2 ivans imports

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Posted 19 January 2014 - 11:19 AM

Black wire with blue stripe off back of dash or ecu

#3 Fairtax4me



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Posted 19 January 2014 - 11:35 AM

Like Ivan said, If the car has a tachometer in the dash you'll have to get your signal from there instead of the coil. Or find the tach signal wire on the ECU.

The waste spark coil packs have a separate negative for each half of the coil, each negative feeds to the igniter, which then sends a signal to the ECU. The ECU sends a signal to the tachometer. The igniter has a ground(-), but its a straight ground, not a switching ground which is what makes a standard ignition coil work.
Theoretically you could get your signal from the igniter, but it would only be a half signal, you would need a converter to make it a full tach signal.

#4 Gloyale


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Posted 19 January 2014 - 01:44 PM

Connector B56, pin 16 at the ECU


It's the bottom corner pin of the second smallest connector.  Black/Blue stripe wire.


You could also grab that wire at the Cruise Control unit too.

Edited by Gloyale, 19 January 2014 - 01:46 PM.

#5 stickedy


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Posted 19 January 2014 - 02:31 PM

Ah, ok, thanks! That helps me a lot!


If I see it right, then the igngition system is basically made of two independent ignition coils? I can made an adjustment in the configuration software of the LPG control unit that there are two ignition coils. I guess that will simply double the reading so that the value is correct. It's much easier to pick the signal in the engine bay than under the dish since the whole LPg wiring harness is in the engine bay. If it's not working, then using the signal from the ECU will be plan B.


Many, many thanks!


Edit: There's no cruise control in that European modell... :(

Edited by stickedy, 19 January 2014 - 02:37 PM.

#6 stickedy


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Posted 23 January 2014 - 06:08 PM

So, I managed to make the wiring today and everything is fine now. I connected the lpg input to one of the wires from the ignition coil pack and changed the setting to 4 cylinders and 2 coils and all works as it should now. Shows 850 to 900 rpm at idle :) Thanks for the infos!

Also tagged with one or more of these keywords: LPG, engine speed, ej22

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