Car idles! But runs after key is removed?!

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Jon k
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Car idles! But runs after key is removed?!

Post by Jon k »

Hey guys the car idles on full fuel and spark control. I still have my motronic ecu in the car doing stuff like idle control valve (going to remove it later) along with output to tach etc. When I remove the key from the car, the car continues to run! What the hell is going on? It sputtered out after like 6 seconds when the motronic was controlling fuel pump relay, but with MS controlling the fuel pump relay, the car like held 900 rpm and i pulled the fuel pump fuse to get it to stop! This is kinda scary - what's happening?

With motronic controlling fuel pump relay - car will sputter out after ~3 - 5 secs, with MS doing fuel pump, it rev'd and I pulled fuse in panic!
Danny
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Post by Danny »

Sounds to me like you have your megasquirt on an perminent live, rather than an ignition switched live. Therefore when you turn off the ignition, your megasquirt continues to see 12 volts and carrys on as normal! The megasquirt needs to be connected to something that stays live during cranking, but also turns off with the ignition.
GTI Mk2, 16v head,8v bottom end, eaton M45 blower, megasquirted on dual fuel!
jsmcortina
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Post by jsmcortina »

I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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Jon k
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Post by Jon k »

James - what would my alternator charge light (do I even have one?!) have to do with it? It never stayed on before - I don't think. I have no idea where this light is you're talking about or why it would cause it to stay on.

It can't be a perminant +12v because the unit does not connect to the laptop while the key is off.
chicksdigwagons
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Post by chicksdigwagons »

We had the same problem when we rewired the engine bay on my buddies Audi. The solution was in the alternator wiring. We mistakingly wired the alternator feed line with the relay for megasquirt, keeping it on through the feedback from the alternator.
Jon k
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Post by Jon k »

chicksdigwagons wrote:We had the same problem when we rewired the engine bay on my buddies Audi. The solution was in the alternator wiring. We mistakingly wired the alternator feed line with the relay for megasquirt, keeping it on through the feedback from the alternator.
And the diode trick worked? What did you end up doing to fix?
jsmcortina
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Post by jsmcortina »

Don't question it, just try it. As I said in the post it fixed the same problem on my car.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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milosch01
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Post by milosch01 »

I have had the same problem with an old DS style GM alternator when the mechanical regulator had arced. Then I upgraded to the internally-regulated type and had to install a diode to get the engine to stop with the key off. Didn't matter if using Megasquirt or not.
Jon k
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Post by Jon k »

milosch01 wrote:I have had the same problem with an old DS style GM alternator when the mechanical regulator had arced. Then I upgraded to the internally-regulated type and had to install a diode to get the engine to stop with the key off. Didn't matter if using Megasquirt or not.
So weird james, going to try it today.
Jon k
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Post by Jon k »

James - where do I want to put the 1N4001? Here is a diagram I found.

Image

Was thinking 85b (terminal 4?) off of "unloading relay".

But I see that it already has an "uncoupling diode"
Jon k
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Post by Jon k »

Anyone? Look at the diagram - isn't there already a diode there?
jsmcortina
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Post by jsmcortina »

You'll have to work this one out yourself.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
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Jon k
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Post by Jon k »

jsmcortina wrote:You'll have to work this one out yourself.

James
I am talking to BMW techs right now - they said the main relay is left on ~3 seconds after key is removed so as to avoid "post ignition". Looks like I need to make another relay.
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