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3 Posts
Discussion Starter #1
My injector is not working for some reason I checked for any contaminates, which was cleared off. Then again some issue so I checked the harness just to make sure. But the voltages were weird. It was 8.3V when off and 5.2 when cranking. Last time a wire broke during which the voltage values were 0V to 12V. Can anybody help me understand this problem


313 Posts
First, I'm gonna assume this is about a Gen2 Duke...
and I may be wrong because you haven't indicated...
so this may only be an experiment in the random psychology or surreal cosmic nature of diagnostics...

Ok, look at it like this:
It is only vaguely productive for you to evaluate injector circuit control the way that you currently are.
I think perhaps that is also [way too many syllables] only to be paraphrasing the idea that won't work.

By the way, super scores for having a DVOM, and for being willing to actually jump in and use it...

But what you should be doing with it instead is
*evaluating the voltage level on the Brown/White wire, via back-probing the socket
*with the injector plugged in
*with the key on
*with the black DVOM lead attached to a legitimate frame and harness ground.

If you do that and you have an actual 12V, then you do not have a power supply issue.
But if you only have around 9 or 10 or even less volts, start back tracking through the diagrams I uploaded...
until you find out where the full 12v exists.
IOW... is it just a poor connection, or a fuse that only looks like it's good, or is it a bad relay??
Stuff like that.

Ok, so now it gets just a little trickier.
If you have 12v at the injector, all you really want to know now is
a) does that 12V also exist on the downstream [Blue/White] side of the injector, with injector plugged in and key on...and
b) can the ECU pulse the Blue/White Injector line.

If you have a test light, you can hook one end to ground, and the probe end into the Blue/White cavity, with the injector plugged in of course, then crank the engine.
If the ECU is pulsing the injector, the test light will toggle on and off.
But there is no reason for the injector Blue/White wire to be in a ground state with Key On Engine Off...
so if you didn't prove 12V on the Blue/White with the key on, and injector plugged in, is the injector electrically open?
Test it's internal resistance, unplugged, with your DVOM. Is injector resistance between 12.8 and 16.8 ohms (corrected)?

If all that works/proves itself good,
go back to the first thing you should have done.
Grab a stethoscope with a long thin probe, and have a friend crank the engine while you listen carefully to the body of the injector. Listen for the cyclic 'clicking' sounds that prove the injector isn't simply stuck.

Sorry bout the long litany, this is sooooo much quicker and automatic when I'm just doing it.
I hope it helps.
Post back, of course, so we know what happened.

001 - Power from Battery.jpg 002 - K30 Relay, from Fuse3.jpg 003 - Gen2 Injector wiring.jpg

3 Posts
Discussion Starter #3
I have checked everything you mentioned, the injector is working. We checked the resistance and directly connected to 12V and the vibration of the injector confirmed it.
The wiring is the issue right now, the ground had 3.3V. I don’t know how was that possible. But to ensure grounding I connected the ground wire (black white) directly to battery negative. If received proper values and injector was working with harness. But now the injector is continuously spraying. When starting the fuel pump there is fuel flow, it does spray and fuel sprays after switching off the entire system.
After which the harness seems to have grounding issues.
checked the wiring not sure what’s wrong, removed my grounding modification, it was cranking it injector wasn’t, added my mods again injector was working in same manner.
What shall I do next??

313 Posts
the ground had 3.3V. I don’t know how was that possible. But to ensure grounding I connected the ground wire (black white) directly to battery negative. If received proper values and injector was working with harness. But now the injector is continuously spraying.
Wait a minute...

are you saying one terminal of the injector connector had 12V on it, and you hooked the 'other' terminal of that connector to battery ground?!?
if so, you just forced the injector to be in a constant spray mode, which is not how it is intended to work.
also, leaving it that way for any extended period of time will ultimately damage the injector, remove that modification.

If you were trying to measure voltage on the side of the injector that the ECU is supposed to toggle on/off to ground,
your DVOM will show not 12V, not 0V, but something in between if the ECU is toggling it.
But... that should be examined with a DSO, not a DVOM.

Without any modifications to the harness, if you listened to the injector while a friend cranked the engine, was the injector clicking?

Also... if you're really not familiar with DSO analysis of inductive solenoid circuits, it is unlikely I can lead you to the correct conclusion in the absence of that experience or that tool.
to wit, attempting to use a DVOM in the manner you keep falling back to is inadvertently misleading you.

What shall I do next??
Stop attempting to diagnose this system with the tools you have available. Take the vehicle to a mechanic who has a DSO and have him check the injector waveform for a possible defective driver inside the ECU.

Also... Did you ever actually check to see if you were also missing 'spark', from the coil wire?

Something tells me that until you get this bird to a mechanic who can just fly through the proper tests to confirm [everything you need to know], you are kinda [spinning your wheels] by wishing you could come up with the right answer, but...

well, do you understand I'm sorta recommending you stop trying to diag this on your own?
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