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Start Up Momentary Switch Wiring


amg

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Hello,

Just wanted to confirm if the following scenario is going to work as I imagine it:

The starter motor relay needs ground to crank the engine.

If I wire an earthed SPST momentary switch on a digital input, select 'Ignition Switch' in PCLink and set the pull up resistor to 'ON' and 'On Level' to 'Low', what would I need to select on the Auxiliary Output, which would be wired to the Starter Motor trigger terminal - 'Cond 1 ONLY -> Ignition Switch'?

I basically want to pass the ground on to the Starter relay via the ECU - is this generally okay to do or shall I just wire the switch to the Starter relay ground directly and leave ECU outside of it?

Thanks.

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Starter Control

 

Starter Control provides ECU managed operation of the Starter Motor.

 

There are two requirements for starter control to function:

 

· A Digital Input Function must be setup as Start Position. This could be a conventional key activated ignition switch or a push button.

and

· An Auxiliary Output Function must be setup as Starter Solenoid. This output should be connected to starter solenoid relay.

 

 

Starter Control Settings

 

Start Switch Mode

 

Selects the mode of starter control. Options available are:

· OFF - No starter motor control by the ECU.
· Test - Use for testing input/output functionality only. When Start Status is active the ECU will activate the Starter Solenoid Auxiliary Output. No other conditions are checked, this could potentially lead to starter damage, engine damage or personal injury if operated at the incorrect time.
· Normal - Behaves the same way a typical vehicle starting system.  The key is turned and the engine will crank until the key is released.  However it offers the added protection of preventing the starter being engaged at a high engine speed and the option to disable starting if the vehicle is not in Park/Neutral or is immobilised. When the conditions specified for Deactivation RPM, Anti-theft Lockout and Neutral/Park  Lockout are met AND Start Status is active the ECU will activate the Starter Solenoid Auxiliary Output. The auxiliary output will stay active until the Start Status turns off OR the the Deactivation RPM is reached.
· Start/Stop - Allows the use of a single button for both starting and stopping the engine.  When the engine is stalled, pressing the button will crank the motor over.  Once the motor is running, pressing the button again will stall the engine.  This mode is suitable for a single start/stop button on the handle bar of a motorbike or jet ski. When the conditions specified for Deactivation RPM, Anti-theft Lockout and Neutral/Park  Lockout are met AND Start Status is active the ECU will activate the Starter Solenoid Auxiliary Output. The auxiliary output will stay active until the Start Status turns off OR the Deactivation RPM is reached. Once the engine is running, if the engine speed is above the Deactivation RPM AND the Start Status becomes active the ECU will apply a 100% Fuel and Ignition cut to the engine.
· Touch Start - Allows a starter motor button (or key) that can be momentarily pressed to start the engine.  The driver taps the button and the ECU will take care of starting the engine.  Typical applications for Touch Start mode would be remote starting or a jet boat. When the conditions specified for Deactivation RPM, Anti-theft Lockout and Neutral/Park Lockout are met AND Start Status is momentarily active the ECU will activate the Starter Solenoid Auxiliary Output until the Max Crank Time is met or the Deactivation RPM is reached.  As of firmware version 5.5.6, pressing the start button again while the engine is running will stop the engine.

 


Starter Deactivation RPM

Specifies the engine speed (RPM) above which the Starter Solenoid Auxiliary Output turns OFF.


Use Anti-theft Lockout

An option to make the Starter Solenoid Auxiliary Output conditional upon Anti-theft status. If set to Yes and Anti Theft Status is Active the Starter Solenoid Auxiliary Output will not function.


Use Neutral/Park Lockout

An option to make the Starter Solenoid Auxiliary Output conditional upon Neutral/Park status. If set to Yes and Neutral/Park Status is OFF the Starter Solenoid Auxiliary Output will not function.


Max Crank Time

 

Used only on Touch Start Start Switch Mode, this is the maximum amount of time the starter will be allowed to crank if the engine does not start.

 


 

Starter control Examples

 

 

Example 1:  Normal Mode with Anti-theft

 

Assume Starter Control is set up as:

 

Start Switch Mode = Normal

Starter Deactivation RPM = 600 RPM

Use Anti-theft Lockout = Yes

Use Neutral/Park Lockout = No

 

With the above settings the ECUs Starter Control would activate the starter motor if:

· Engine speed is less than 600, and
· The anti-theft signal is off and
· The driver presses the start button (or turns the key).

 

 

Example 2:  Start / Stop Mode with Neutral / Park Lockout

 

Assume Starter Control is set up as:

 

Start Switch Mode = Start / Stop

Starter Deactivation RPM = 550 RPM

Use Anti-theft Lockout = No

Use Neutral/Park Lockout = Yes

 

With the above settings the ECUs Starter Control would activate the starter motor if:

 

· Engine speed is less than 550, and
· The Park/Neutral signal is active and
· The driver presses the start/stop button.

 

With the above settings the ECU would apply a 100% cut to both fuel and ignition if:

 

· Engine speed is greater than 550, and
· The driver presses the start/stop button.

 

Note: The fuel and ignition cut will remain until engine speed is zero RPM.

 

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  • 1 month later...

Slightly different to the above situations, with my car, I'd like to try and use the standard one push start button being a later model BMW our great friend CANbus is everywhere, but there are some switching 12v sources when the master relay flips a basic rundown of what I'd like to do is:
-Push start button
-Master relay goes active; 12v throughout car
-ECU detects 12v activity around the same time ECU powers up, DI as above most probably. (There is actually a 2 stage accessory and then ignition power key procedure like any other car, however, most of the time they happen almost simultaneously, unless the clutch is not depressed, etc.)
-ECU triggers start relay
-When 12v is taken away, ECU will turn off, engine dies normally 

In the event of a stall, the car would have to turn off the 12v DI source and re-energise it in order to power the starter motor again. 
Does this sound possible?

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  • 4 years later...

I'd like to wire in the Start/Stop button and use the system described above. That all makes sense with wiring in the button from a switched ignition source, then to an ECU DI and then connect the starter relay to an ECU Aux Output. However I'd also like to keep the key system active as per the OEM setup where the key is turned to the STA position and provides 12V to the starter relay. However to achieve this it would be apparent I need to connect the key STA wire to the same wire the ECU Aux Output is connected to. This would make it so the ECU could see 12V to the Aux Output which I assume is bad. Would adding in a diode to the Aux Output wire stop the ECU getting back fed 12V into an output?

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In most cars the starter switch would excite the solenoid directly, whereas the ecu aux would only be switching the coil of a relay to drive the solenoid, so assuming yours is like this they should be isolated from each other. 

Mlw7UFu.png

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The key currently switches the relay coil to drive the starter solenoid. I was going to use 1 relay for both key and ECU and use both to power the coil of that relay.

Based on the diagram I should be using 2 relays instead of trying to use a diode to split the circuits?

I still think a correctly specified diode would work here. It's a brand new engine harness and fuse/relay box so I have no issues with being able to install the diode inline with the ECU output. Although I am expecting the ECU to output 12v to switch the relay if I am correct.

 

 

 

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ECU is a Monsoon X. Fuse and Relay box is the MaxxECU one. Planning to use Aux 6 for the relay coil. DI 3 for the start/stop button/key input.

Just doing some research as I type this post and looking at how the other relays operate based on the LINK Power Supplies diagram and the way the fuse and relay box is wired and I now understand that none of the relays are supplied 12V to the coil from the ECU, they are all grounded through the ECU.

The Starter and ECU/Main Relay are grounded to the chassis however.

I have spoken with the owner and we have decided that it is better if we reduce the complexity of the system and do the following.

  • As per the first line, use DI 3 for the start/stop button input and wire 12V from the ignition switch to the button.
  • Also wire the STA position from the key to the same DI 3 input.
  • Then wire 12V to the starter relay coil pin 86 after the ECU/Main relay so it only gets power with ignition ON
  • Use Aux 6 to ground the starter relay coil pin 85 and program the ECU to use Example 1 or similar in Simons post above.
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Yes a second relay would be an option but I have managed to modify the fuse box easily without cutting anything to make this happen.

Thanks for your help on this. I'm new to ECUs and DI and Aux things but I now have a better understanding of it. If I go back and look at how the GEN4 3SGTE from the Caldina is setup with 12v controls for valves I see the same pattern. Wiring I mostly get but how ECUs operate is a different thing.

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One last question. Do I provide 12V to the switch to be grounded through the ECU DI pin or should I be grounding the switch and activating the Pull-Up resistor as per the example in the help menu for Pull-Up Resistors? Or can I do it either way?

The way the key is setup, this would provide 12V to the ECU so I would assume I have to match this with the Start/Stop button due to them both being wired to the same DI pin and therefore not activate the Pull-Up resistor. I feel I have answered my own question.

At this point in time the ECU is connected to a power supply and the PC and not the engine/car so I can't test it, I haven't even done the wiring harness yet but I have everything mapped out.

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