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Checking your injectors electrical circuits
Published by Deckchair5
22-07-2007
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Checking your injectors electrical circuits

You may have an injector fault and you wonder “Is it the wiring or is it the injector?”
Here’s an easy method to check the wiring to your injectors

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12volt is constantly supplied directly to all the injectors N70 (wire MB in this wiring diag for a 1.6 Stilo MB = Brown and White)
And each injector timing is done by the ECU by supplying a path to earth
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An injector is a simple electrical solenoid valve which opens and closes the injector to spray fuel into the cylinder. This picture shows the actual connector on an injector which you can test for continuity using this method without actually needing to physically get at it

Just for reference here are the Italian wiring codes

N= BLACK
B= WHITE
C= ORANGE
M= BROWN
A= LIGHT BLUE
S= PINK
V= GREEN
R= RED
Z= PURPLE
G= YELLOW
H= GREY
L= BLUE

Ok Now each injector solenoid should be a closed circuit i.e. a continuous electrical path with no breaks so if we check the resistance of each circuit they should all be the same, on my 1.6 Stilo they were each 15 ohms. That's the resistance through the solenoid coil. The actual figure isn’t so important but that they should all be the same
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Injector multi connector D81 just lever up catch and pull to disconnect

So with ignition switched off and a cold engine disconnect the D81 connector and using your multimeter check the resistance between the 12v supply pin and each injector pin. The 12v supply pin is easy to spot as it’s the extra large one in the centre of the 5 pins in there. Do each circuit in turn (always one probe on the 12v supply and the other on one of the other pins) and they should all be the same. No circuit at all (infinitely high resistance) or zero resistance would show a wiring fault or injector solenoid burn out.

Be clear what you’re testing here though, you are testing the integrity of the wiring circuit to the injector, the injector internal solenoid for continuity, the connection of each injector connector and the earth supply back to the D81 connector.
Thanks gearfinger, bigfathairybiker thanked for this post
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Old 24-07-2007   #1
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Re: Checking injectors electrical circuits

Excellent guide - cheers, where is the D81 wire?
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Old 24-07-2007   #2
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Re: Checking injectors electrical circuits

Haven't found it yet?
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Here it is
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Old 24-07-2007   #3
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Re: Checking injectors electrical circuits

Quote Originally Posted by Deckchair5 View Post
Haven't found it yet?
Attachment 30846
Here it is
Cheers found it - done the test - 2 were not reading anything, while others read 16ohms, then was playing about with the different pins, i.e. resistance between them - and then checked one last time and all four had 16ohms, does this mean the 2 injectors which i pressumed were faulty due to the OBD diagnostic tool, have faulty wiring, which casues the EML to come and while the car starts to jerk.

If there is a fault in the wiring, does it mean i odnt have to change the actual injectors??? .

took it to fiat hooked it up and then said, no problems with it, but then on the way home EML came up, taking it back tommorow.
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Old 24-07-2007   #4
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Re: Checking injectors electrical circuits

also any guide on how i get to the actual injectors.
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Old 24-07-2007   #5
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Cool Re: Checking injectors electrical circuits

Right strip down that one .. inlet manifold has to come off
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Old 24-07-2007   #6
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Re: Checking injectors electrical circuits

Quote Originally Posted by PNL View Post
Right strip down that one .. inlet manifold has to come off
no it dont
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Old 24-07-2007   #7
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Re: Checking injectors electrical circuits

Quote Originally Posted by PNL View Post
Right strip down that one .. inlet manifold has to come off
Inlet mainfold is accessed via the front grill or from under the car!
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Old 25-07-2007   #8
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Re: Checking injectors electrical circuits

done the test - 2 were not reading anything, while others read 16ohms, then was playing about with the different pins, i.e. resistance between them - and then checked one last time and all four had 16ohms, does this mean the 2 injectors which i pressumed were faulty due to the OBD diagnostic tool, have faulty wiring, which casues the EML to come and while the car starts to jerk.
Like it says in the guide, if the resistance is the same- around 15 ohms - in all the circuits then all the circuits are good. Zero or a much higher resistance would indicate a problem in the circuit
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Re: Checking injectors electrical circuits

Right...I'm a newbie here, so please pardon my ignorance/stupidity!

I'm getting the Engine Management Light on the dash randomly. Sometimes it's there, sometime's it's not. Occassionally when I start the engine, it ticks over for a second, then cuts out, and takes maybe 3 or 4 attempts to get the engine to run properly. I took the car to the local garage (having had a very bad experience with the Fiat dealership in this area!) and the diagnostic test indicated a problem with the injectors/wiring to the injectors.

So, would carrying out the checks in this original post be a good starting point to determine if it's the wiring/injectors?

If it is, and it turns out that the problem is the wiring, what'd be the next step? New wires/loom?

Cheers for any help or advice, Andy.
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Old 06-12-2011   #10
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Re: Checking your injectors electrical circuits

Took me a while to get around to needing this guide, engine warning light came on, dragged out the old OBD cable (Hadnt required it since last winter to be fair) and found injection issues on no 3, turns out the injector is very high resistance. So one new (to me) injector later and a few resets, and everything is working again.
Thanks for the guide and wiring diagrams Decks.
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