Injector polarity
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Part of the Furniture
Joined: Jun 2005
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From: Cheshire, CT USA
Injector polarity
poking around in my engine compartment today, while changing out the marelli to coil on plug, I notice the inejectors are getting fed the wrong polarity. They are marked + on the injector but that isnt whats + on the wiring as verified by a meter. Everything seems to work for the most part, should I bother trying to fix it?
Its a big turbo motor and green injectors.
Also finding crappy motor ground (800 ohms to ground) and a strange injector flutter when I turn on the key. The injectors seem to fire for about half a second when I turn the key on, before I even crank.
bob
Its a big turbo motor and green injectors.
Also finding crappy motor ground (800 ohms to ground) and a strange injector flutter when I turn on the key. The injectors seem to fire for about half a second when I turn the key on, before I even crank.
bob
Too many posts.. I need a life!!
Joined: Jan 2005
Posts: 888
Likes: 3
Re: Injector polarity
Taken from an automotive engineers site I lurk on
It would appear then that the + marking is to aid diagnostics or assembly.
I have been testing and designing electronic fuel injectors for more than two decades and have yet to figure out why Bosch and some others indicate polarity. There is nothing but a coil inside conventional electromagnetic injectors. I have done extensive magnetic testing and there is a small difference the shape of the first pulse when you reverse polarity due to hysterisis. Any trace of this is gone by the 3rd pulse so it is insignificant.
There is a significant back EMF when the magnetic field collapses but this is absorbed by either an RC or (more commonly) zener circuit in the ECU. The breakdown voltage of the insulation is typically more than an order of magnitude higher than the back EMF voltage.
Siemens, Delphi, ourselves and many others do not indicate polarity.
There is a significant back EMF when the magnetic field collapses but this is absorbed by either an RC or (more commonly) zener circuit in the ECU. The breakdown voltage of the insulation is typically more than an order of magnitude higher than the back EMF voltage.
Siemens, Delphi, ourselves and many others do not indicate polarity.
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