Where to pick up the Ignition Signal?

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okubricko
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Where to pick up the Ignition Signal?

Post by okubricko » Thu Nov 30, 2017 9:09 pm

Quick question for everyone. Where did you pull the signal from for the Ignition that goes to the 86 on the Main and Fuel Relay. I have a 73 Super Beetle and am pulling it off of S12 in the fuse block. The fuel pump relay is clicking on and off and ruining any signal I am getting. Any help would be greatly appreciated.

In the meantime, I am going to rewire the relays. Thanks

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Piledriver
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Re: Where to pick up the Ignition Signal?

Post by Piledriver » Thu Nov 30, 2017 11:14 pm

So you are still using the distributor/fuel only as "simple trigger"?

That's the least tested setup as very, very few folks use it.(probably nobody here)
Folks here typically use a crank trigger, or a missing tooth wheel-in-distributor setup with a waste spark coil or ls2 coils.

In any case, it's usually best to get the signal directly off the source, if your ecu is set up for that.
Probably best to ask on msextra forums.
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okubricko
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Re: Where to pick up the Ignition Signal?

Post by okubricko » Fri Dec 01, 2017 7:18 am

Sorry, I guess I was confusing in what I posted. I am using a crank trigger from Mario, I was talking about where do you pick up the signal from the key that connects to the two relays. See the blue circle in the picture.
Ignition Point.JPG
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ps2375
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Re: Where to pick up the Ignition Signal?

Post by ps2375 » Fri Dec 01, 2017 9:14 am

That's not a "signal", that is 12V switched.

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Piledriver
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Re: Where to pick up the Ignition Signal?

Post by Piledriver » Fri Dec 01, 2017 9:20 am

EDIT: ^^^^ what he said, that's switched power, not a "signal" line.

You would simply use the ignition coil switched power line to control the main relay.
That relay in turn powers the ECU, FP relay is controlled by the ECU via the violet wire.
My FI t3 had a tap off key/ign power under the back seat to run the djet main relay, and ~all the wiring goes by there in any case.

If the fuel pump relay is turning on and off continuously with key on, that indicates a config error.
If it cycles only when cranking, possibly signal issues.

IMHO, and contrary to the official instructions, the engine is the absolute last thing I would connect any ECU grounds to, esp signal grounds. (power grounds like for coils OK)
Signal grounds should ground back at the ECU.

My ECU and all the relays etc live on an aluminum plate under the back seat, which is very well grounded to the battery with a short fat pair of 12 ga wires. YMMV.
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okubricko
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Re: Where to pick up the Ignition Signal?

Post by okubricko » Fri Dec 01, 2017 12:25 pm

Ps2375 >> you're absolutely correct. I misspoke but I guess that gets to the meat of my question. Where is the best spot (fuse location or other) to get the +12v for this?

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Piledriver
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Re: Where to pick up the Ignition Signal?

Post by Piledriver » Fri Dec 01, 2017 3:43 pm

Ignition power wire for the control, and the battery for direct power.
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okubricko
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Re: Where to pick up the Ignition Signal?

Post by okubricko » Sat Dec 02, 2017 3:05 pm

ign_plug.gif
If this is the output of the ignition switch I should get the +12v from 15. Correct.

I read that if you use X the the headlight power gets cut during cranking.
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ps2375
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Re: Where to pick up the Ignition Signal?

Post by ps2375 » Sat Dec 02, 2017 5:50 pm

okubricko wrote:
Sat Dec 02, 2017 3:05 pm
If this is the output of the ignition switch I should get the +12v from 15. Correct.
Correct.

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