injector issue

~NASTYSTROKER96~ · Jan 20, 2012

i just put injectors in my truck last weekend and its been havin an injector miss fire ever since, me and a buddy pulled the covers back off and found that the front injector on the driver side is only gettin 20V? we put a new valve cover gasket with harness on and still is only gettin 20V? could the idm cause this?

Tom S · Jan 20, 2012

I am not sure on the voltage value. However sure the IDM could cause a misfire but I would not think that would be all that likely to coincidentally happed right when you swapped injectors. Did you watch it run with the valve cover off?

woodduck97 · Jan 20, 2012

You need a special meter to read the voltage going out to the injectors because the signal is to fast for a standard meter to detect. If you have a another IDM to swap I would try that. If that does not work you may have possibly torn a oring when installing the injectors causing ur problem. Also how long have you driven the truck since the install? To help narrow the problem down if it is missing at a idle as well have the valve covers off and unplug the injectors one by one to figure out which one is not hitting as well. Then swap that injector into another cylinder and drive the truck to purge the air and follow the steps again to see if that is the problem injector.

~NASTYSTROKER96~ · Jan 20, 2012

ive only drove it around town alittle bit, dont want to drive it too much with it running like it is, it runs rough all through the rpms and you can hear a miss, we have ran it without the covers on it and pulled each plug and found that one injector to be firing very weakly with it showing less volts than the others. you can be goin and the torque converter locks in and it starts shaking real bad. would i need to run a buzz test to see if it is that injector for sure?

woodduck97 · Jan 20, 2012

If you have a scanner to run a buzz test I would to see if you hear a weak selonoid.

neverkickn · Jan 20, 2012

This procedure will allow you to test the whole circuit from the idm plug to the injector.

Make sure you dont pierce the wires with the voltmeter. The injector wires have electro magnetic shielding that should not be damaged. Unplug the harness from the idm and connect to the pins.

~NASTYSTROKER96~ · Jan 20, 2012

nice i might try that, could the plug goin into the valve cover be bad too?

neverkickn · Jan 20, 2012

~NASTYSTROKER96~ said:
nice i might try that, could the plug goin into the valve cover be bad too?

if you have an open somewhere then it could be anywhere. If it doesnt ohm out good, then you start unplugging stuff and testing the harnesses individually.

Is the idm on an obs hard to get to? Reason I ask is if it is it may be easier to check the vc harness and injector solenoid first.

Let me see if I can find the vc gasket pinout sheet and the ohm spec.

neverkickn · Jan 20, 2012

Couldn't find the diagram but if you unplug the harness from outside the vc, the center pin is common and the pins on the left and right are for the injectors. The outer pins are for the glow plugs.

You should read 2.5 to 3.5 ohms. If you get a bad reading on an injector then you will need to pull the vc to check the solenoid by itself. If everything is good then you will need to test the harness back to the idm. If it is in the wiring, it should show up somewhere in that test.

Is the problem intermittent or constant? Have you ruled out a mechanical problem?

~NASTYSTROKER96~ · Jan 20, 2012

the problem is constant, only started doin it after i swap injectors, but i dont see how the injector would be bad if its only gettin low voltage to it? i just replaced the connector and its still doin it

neverkickn · Jan 20, 2012

You have to start somewhere. You need to rule stuff out till you find the problem starting with the most likely. Are you sure you got the injector seated all the way? Have you pulled the vc's to see if there is excessive oil or no oil coming from this injector?

I have no idea what you should see on a meter when reading voltage as the injector fires, but I am pretty sure you aren't going to get an accurate reading with a standard meter.

If you suspect an electrical problem with that one injector then you need to ohm the wiring. You replaced the vc gasket and uvch's right? So the only thing left is the solenoid itself, the wiring harness, and the idm.

The other alternative is a mechanical problem. Something like the injector has internal issues or you didn't seat the injector all the way or you damaged an oring on the injector during installation.