Irregular voltage from Injector 3

[mooseclap05]

Hi all, Cyl 3 is dead. Running on 5. Checked for the plug, spark, coil pack (All are fine). Finally got around to measuring the voltage and it isn't reading 12 volts like all the others. The meter instead reads around 2~3~4 volts. Question is my injector bad? or is my ecu bad? or is the wiring between the ecu and the injector bad? Also, I went ahead and soldered a injector female plug with extended wires so i can directly test the wire upstream to the ecu. is my thinking right on this? any help is appreciated. I was working on this with DAZ just a couple nights before he past away, which saddens me . RIP. Unfortunately, after learning the sad news i walked away from the car for a bit in dismay, but DAZ would have wanted me to finish this build so I'm in it till she blows and then some more.

[vavJETTAw36]

What voltage are your other injectors?


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[DieselElectric]

Injectors are controlled by the ECM cycling the ground.

They should all be wired straight to a 12v source.

If 5 of the 6 injectors are getting a 12v when measured from the positive on the connector to ground (don't use the ground on the connector), and one has low voltage, check your wiring.

Usually the positives splice off at the injector harness (not sure on this platform), but I would start peeling away the loom and closely inspect the injector harness.

[mooseclap05]

Injectors are controlled by the ECM cycling the ground.

They should all be wired straight to a 12v source.

If 5 of the 6 injectors are getting a 12v when measured from the positive on the connector to ground (don't use the ground on the connector), and one has low voltage, check your wiring.

Usually the positives splice off at the injector harness (not sure on this platform), but I would start peeling away the loom and closely inspect the injector harness.

The PO replaced the engine wire harness at Audi..lol So DAZ was thinking it could be a bad ECU, or bad wiring, or a open injector

[mooseclap05]

Also takin a noid light to it today

[DieselElectric]

The PO replaced the engine wire harness at Audi..lol So DAZ was thinking it could be a bad ECU, or bad wiring, or a open injector

Ecu wouldn't effect your voltage to the injector. There is a fused positive line going straight to all of the injectors when the key is on, and the ECU fires the injectors by actuating the ground. Voltage does not come from the ECU, so you can eliminate that from your possible culprits.

Injector won't have any effect on your voltage.

How did you get your voltage reading?

The fact that the harness was changed just gives more reason to look into it.

Test voltage with the injector disconnected and connect your negative lead to the battery ground. If you don't have 12v, but have 12v on the other injectors, then the problem is likely only a few inches into the harness.

[mooseclap05]

How did you get your voltage reading?

Right off the 2 wires coming out of the female plug to the injector

[Nollywood]

Right off the 2 wires coming out of the female plug to the injector

You need to measure from the switched 12V feed to ground. Measuring across the terminals will not provide any reliable readings. The ECU triggers the ground to each injector in pulses.

Measure V from terminal 1 for injector #3 connector to the cylinder head. This is a common switched 12V to all the injectors, so make sure the ignition is in the "on" position.

This connection is straight from the chassis connector under the ECU, and is spidered to all 6 injectors. As the rest are working, the break in most likely to be after the nearest injector, so pretty easy to locate. Find it, repair it.

[mooseclap05]

Thank you

Locating now

[mooseclap05]

Got an extra hand to turn the key "on" ignition. looks like I'm getting 12v for a split second.

"Measure V from terminal 1 for injector #3 connector to the cylinder head" where is terminal 1? the diagram photos I'm seeing are distorted.

[DieselElectric]

Plugs are usually numbered. Bust out your magnifying glass if need be.

[mooseclap05]

Found it! PO mis-installed the injector plug to the N80. i switched them and its running on all 6 now!

[zillarob]

I hope it wasnt like that for long
Have an allroad out front with 0psi comp in cyl 3 because they ran it like that.

[vavJETTAw36]

Wait what did the po do? Just didn't plug the n80 in?


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[zillarob]

They are the same connector and kind of in the same neighborhood so you can swap them if you try.
It is pretty obvious where they go if you just look at the harness so hard to fk up.

[mooseclap05]

They are the same connector and kind of in the same neighborhood so you can swap them if you try.
It is pretty obvious where they go if you just look at the harness so hard to fk up.

Ya, i unplugged the hats and figured it out real quick lol

Also its running great, been driving it all day. Missed those 2nd gear pulls lol