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Author: Subject: Silly question alert...
James24785

posted on 8/5/18 at 06:30 PM Reply With Quote
Silly question alert...

Im currently in the middle of a rewire and fitting some new switches. I want to fit a push button start, but will be retaining the standard ignition barrel for now.

Do I just switch 12v to the small connector on the starter motor?

Also can I take a feed from the dash battery warning light to illuminate my push button? Push button will illuminate on ignition, and then go out once the engine is running.

Told ya it was a silly question. Well, two



Cheers

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gremlin1234

posted on 8/5/18 at 06:45 PM Reply With Quote
1, yes that should work
2, though it seems a good idea, no, it may not work, because many alternators use the light as a reference, and can screw up charging.
(you would probably be ok with and led for the button illumination.)

and, no, not a silly question!

edit:
but maybe you could use the oil pressure warning to light the button

[Edited on 8/5/18 by gremlin1234]

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James24785

posted on 8/5/18 at 06:48 PM Reply With Quote
Brilliant, cheers.
I take it the trigger for the starter motor pulls very little current, and should be fine without a relay?

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gremlin1234

posted on 8/5/18 at 06:56 PM Reply With Quote
quote:
Originally posted by James24785
Brilliant, cheers.
I take it the trigger for the starter motor pulls very little current, and should be fine without a relay?
the starter circuit has the relay/solenoid built in, but do use a good quality button/switch (at least 5A)

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big_wasa

posted on 8/5/18 at 07:04 PM Reply With Quote
The starter motor solenoid draws something like 10a continues and a higher initial spike.

The old sierra switch handles that but newer stuff uses a relay.
I use a relay.

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James24785

posted on 8/5/18 at 07:05 PM Reply With Quote
Using a savage switch, which I think is rated to 15A if I remember correctly
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James24785

posted on 8/5/18 at 07:06 PM Reply With Quote
I think I'll just chuck a relay in to be safe
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gremlin1234

posted on 8/5/18 at 07:13 PM Reply With Quote
quote:
Originally posted by James24785
I think I'll just chuck a relay in to be safe
yep that seems sensible

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dave r

posted on 8/5/18 at 07:43 PM Reply With Quote
also if you feed the relay from the oil switch , you can disable the starter button, after the engine fires
it saves mates in the car pressing buttons when you are driving along and engaging the starter





I'd love to give my imaginary friend a great big hug,

but this jacket makes it impossible.

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James24785

posted on 8/5/18 at 07:47 PM Reply With Quote
Not a bad shout that!
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birdii

posted on 9/5/18 at 09:35 AM Reply With Quote
I've added a savage start switch to my car this last weekend - decided to go with a relay for a reliability.

I have used the charge indicator as illumination but my car has a different charge light system, its one of those little boxes for classic vehicles which illuminates a warning light when your voltage drops below 12.5V, i had to do this as my alternator choice didn't have a warning light connection. This has worked perfect for me.

I also considered the oil pressure switch as a safety but then thought it could be a real irritation - engines can definitely put the oil light out while cranking, if that happens before it starts you would be screwed.
I also considered using a configurable output from my emerald ECU, i'm sure i could fudge one of the options such as VVT activation and use the output as a switch to enable/disable the starter relay around a certain RPM point. Decided in the end that it shouldn't be necessary and i put my button to the right of the steering wheel so passengers can't fiddle.
Dan

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Mr Whippy

posted on 9/5/18 at 09:59 AM Reply With Quote
if you have a steering lock and this is disabled by the ignition key, then insure the starter button is fed by the ignition switch

otherwise what will happen is you will jump in the car start the engine and drive off with the steering lock still on...I know this from experience

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jps

posted on 9/5/18 at 10:30 AM Reply With Quote
Sort of related - I was wondering if there is benefit to being able to crank the engine without ignition to raise oil pressure before starting it each time? Having a 'start' button, and a separate switch to make ignition 'live', would enable this?
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SPYDER

posted on 9/5/18 at 10:47 AM Reply With Quote
^^^^^^ Meanwhile, whilst you are cranking you are filling the (probably cold) cylinders with unburnt fuel, effectively washing the bores.
If there was any benefit to your proposed strategy then manufacturers would be using it.

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jps

posted on 9/5/18 at 10:54 AM Reply With Quote
quote:
Originally posted by SPYDER
^^^^^^ Meanwhile, whilst you are cranking you are filling the (probably cold) cylinders with unburnt fuel, effectively washing the bores.
If there was any benefit to your proposed strategy then manufacturers would be using it.


Good point - I mentioned it because 'turn it over with no spark to build oil pressure before starting' was advice i got on a thread I posted about recommissioning my Pinto...

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SPYDER

posted on 9/5/18 at 11:17 AM Reply With Quote
If "recommissioning" then I might agree. I will be doing something similar when first starting my new engine build but I will drive the oil pump directly to build pressure. In general use though, no.
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HowardB

posted on 9/5/18 at 11:18 AM Reply With Quote
quote:
Originally posted by jps
quote:
Originally posted by SPYDER
^^^^^^ Meanwhile, whilst you are cranking you are filling the (probably cold) cylinders with unburnt fuel, effectively washing the bores.
If there was any benefit to your proposed strategy then manufacturers would be using it.


Good point - I mentioned it because 'turn it over with no spark to build oil pressure before starting' was advice i got on a thread I posted about recommissioning my Pinto...


You could have it a switch to isolate the fuel pump - then ignition is not important, and it would be possible to crank without firing,... should you wish





Howard

Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)

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