Knock box + ICM wiring diagram?

29256 Views 33 Replies 12 Participants Last post by VenousSAGE, Apr 26, 2022

ncbrock

Discussion Starter · Dec 26, 2011

I decided to run a knockbox and a 7 pin icm setup with my carbs and am having trouble finding a good diagram to follow. Ive been searching for a while and cant turn up what I need. All I can find are people saying "Yeh, I run a knockbox setup"

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ncbrock

Discussion Starter · #21 · Jan 5, 2012

well if i knew what terminal everything came from nothing would be a problem. how are you supposed to tell what terminal a wire comes from when the connector prevents you from seeing anything?

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YJSAABMAN

· #22 · Jan 7, 2012

ncbrock said:
well if i knew what terminal everything came from nothing would be a problem. how are you supposed to tell what terminal a wire comes from when the connector prevents you from seeing anything?

This makes no sense. The connector is what tells you which terminal. Let's try this a different way...

Does your mystery wire come form the knock box or the ICM?

With the (insert source of mystery wire here) sitting flat on the mounting surface on a table with the connector facing you start at the left pin (#1) and count to the right until you get to your mystery wire.

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ncbrock

Discussion Starter · #23 · Jan 11, 2012

Im not sure about your knockbox connector, but my knoxbox connector is just a bundle of wires that runs into the connector. There would be no telling what wire came from what terminal.

By ncbrock at 2012-01-10

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YJSAABMAN

· #24 · Jan 11, 2012 (Edited)

Either the plug or the knock box will have at least 4 numbers on the connector, one at the start and end of each row. I forget exactly how the knock box is laid out.

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doctor12valve

· #25 · Jan 12, 2012

ncbrock said:
Im not sure about your knockbox connector, but my knoxbox connector is just a bundle of wires that runs into the connector. There would be no telling what wire came from what terminal.

By ncbrock at 2012-01-10

Call us tomorrow, I'll order you one :thumbup:

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ncbrock

Discussion Starter · #26 · Jan 12, 2012

ive got that one and a golf\jetta one. Unless you spend a lot of time studying the current flow diagrams, they dont make a whole lot of sense. I can make out some things but id need someone that knows what they are looking at beside me to tell me 100%

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revolution_Jd3

· #27 · Nov 11, 2012

old thread... hope you got it whooped. if not figured i throw this in here for further peoples searches.

http://www.driversfound.com/scirocco/techtips/engine/knocksensor/

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YJSAABMAN

· #28 · Nov 18, 2012

revolution_Jd3 said:
old thread... hope you got it whooped. if not figured i throw this in here for further peoples searches.

http://www.driversfound.com/scirocco/techtips/engine/knocksensor/

Great addition to this thread! :thumbup:

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MacGruber

· #29 · Jul 13, 2020 (Edited)

WATCH OUT for the screwy wiring advice here.
"Drivers Found" is just another Vortexer who can make a mistake like anyone.

That mystery wire from the KNOCK BOX to the STARTER 50 (Solenoid 12V during cranking) ncbrock has an issue with, supposedly from T10 on the Knock Box. Obviously there is no reason at all to send 12V into T10 of the Knock Box during starting.

T10 in fact is a R/Y wire added to ground the 4-pin CIS-E fuel pump relay and turn it on. So add the new wire or use the old relay.

Fuse 17 was reserved for the Knock Box power supply requiring another new wire.

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betterfood

· #30 · Oct 31, 2020

I'm working on a carb + knock box + ICM setup right now. I took my knock box apart to sort out this T10 thing.

My box is part number 811 907 397 E. The one with yellow lettering. Cannot guarantee the internals are the same for the other one(s).

T10 is connected directly to the collector of an NPN transistor, a BC337 to be exact. The emitter is connected directly to ground (T3).

This make sense, as MacGruber stated, it drives the low side of the fuel pump relay. I can only assume this is done so the fuel pump does not run all the time when the ignition is on and the engine is not turning. The knock box does this rather than the fuel computer as it's the one with the RPM input.

Time for some assumptions and a hypothesis.

Assuming I am correct in that the fuel pump will be shut off in the absence of RPM. I also don't think these cars prime the fuel system, otherwise there would be no point to the fuel accumulator, the knock box could issue a prime pulse, I'm not sure. This means when you turn the ignition on you will see 12V on T10 through the fuel pump relay coil while the pump is off. While cranking you will still see 12V while the knock box gets synced to the RPM signal, and then probably a bit of a delay in your meter. Once RPM is detected and the transistor is turned on current will flow though the relay and you will then see 0V on T10 just about at the same time you stop cranking. This makes it look like T10 is receiving power during cranking and I bet the origin of the powered T10 myth.

What does this mean for people who connect T10 to 12V? You killed the transistor and it doesn't do anything anymore. Which is fine because if you weren't using T10 as originally wired you don't need it anyways.

Unless of course there are different knock boxes that do different things with T10. In which case this only applies to the E variant. Everyone send me your knock boxes so I can take them apart!

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MacGruber

· #31 · Nov 1, 2020 (Edited)

Take a look at the Bentley schematic for Engine Controls - 16-valve Scirocco and notice the +12v wire running FROM the starter (called 15a) - actually 2 wires,
one to the Cold Start Valve.
one to the ECU T24 - a cranking signal.

No starter wire leads to the knock box.

How does the fuel pump prime? My CIS car primes via the large fuel pump relay receiving ignition switch +12v. If the pressure is already high enough the fuel pump doesn't do anything.

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[email protected]

· #32 · Nov 2, 2020

MacGruber said:
How does the fuel pump prime?

IIRC the knock box primes the pump at power on for a second, then it shuts the pump off until until the engine starts turning (hall input).

MacGruber said:
If the pressure is already high enough the fuel pump doesn't do anything.

strange, there is no fuel pressure switch or sensor so I"d say the fuel pump priming is not pressure related..

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betterfood

· #33 · Nov 2, 2020

MacGruber said:
Take a look at the Bentley schematic for Engine Controls - 16-valve Scirocco and notice the +12v wire running FROM the starter (called 15a) - actually 2 wires,
one to the Cold Start Valve.
one to the ECU T24 - a cranking signal.

The scheamtic I am going of shows a "cranking" wire to T24 on the fuel computer as well. Not sure why the CIS computer cares though. On an electronic injection system it would go into a different cranking map. On CIS the cold start colenoid is driven directly from off the starter. Must do some other stuff durring cranking. Regardless I think we both agree T10 does not go the the starter.

[email protected] said:
IIRC the knock box primes the pump at power on for a second, then it shuts the pump off until until the engine starts turning (hall input).
strange, there is no fuel pressure switch or sensor so I"d say the fuel pump priming is not pressure related..

That's exactly what I was going to ask/say. Even if there was a pressure switch, the knock box controls the fuel pump and it definately does not have a pressure switch input.

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VenousSAGE

· #34 · Apr 26, 2022

Bump, having similar issues with my swap, im integrating a knock box from an 87 16v scirocco into an 85 8v harness.

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