Injectors not pulsing..need help

[1976CamaroGuy]

Ok, I need some help as I can’t figure out what’s going on.


My engine is a 2004 5.3 with LS1 injectors, Intake, coils and DBC throttle body.


The PCM is a 2004 express Van tune with the blue / green connectors.


I have fuel and spark but no injector pulse. I’m unsure where to look at this point. I have power at the injector on the 12v side but the noid light isn’t lighting up when I crank the motor.


Keep in mind this engine was running fine before I decided to move the PCM inside the car to clean up the engine bay. It has vats delete already in the programming and nothing has been changed there.


I re-wired and rebuilt my harness by shortening wires and added new wiring for most of the wiring. I meticulously labeled everything and doubled checked twice before inserting wire into pcm connector.


I also over-grounded the harness by putting ground terminals for inside the car and back of the engine head. Everything soldered and goes to each point. I also added grounds from the motor to firewall and motor to frame. Battery ground is on the engine block.


Here’s what I have done so far:


• Verified spark with a spark plug ignition tool (It lights up when cranking


• Verified fuel pressure with a gauge on the fuel rail @ 58lbs. Fuel squirted out of the rail and you can hear the pump priming when turning the key switch on.


• Verified 12 volts on the pcm and sensor circuits when cranking


• Verified motor will actually run by squirting starter fluid inside the throttle body


• Checked all grounds, including back of the head and inside the car.


• Pulled codes with a reader, at first I got a P0107 with meant issues with map sensor. I pulled the plug and checked 5v reference and low reference on the terminals..both were good so I put the plug back in. Cleared codes and checked again. Check engine light is still on but no codes now. I’m guessing the plug was partially out of the map sensor or something.


• I checked PCM grounds on terminals blue connector 1, 24, 27, 40, 64, 67 and green connector 1 and 40…..all were good.


• Battery has a full charge


• Checked fuses on my main fuse block for the harness, all good.


What can cause the injectors not to pulse? I was monkeying around with it for a split second last night and got it to work for one start cycle.


The noid light was working too. But for some reason it quit and I can’t duplicate it.


I need to check the wiring at the crank and camshaft sensor next but I am running out of ideas and the fact that I am not getting codes for either is making me less than optimistic about it.


I just don’t know why the check engine light is on.


It’s got to be something simple, just not sure where to look


Thanks in advance

[andrewb70]

Sounds like you need to double check everything that you did.

The injectors get constant +12 and the ECU triggers a ground signal to fire them. Hope that helps a little.

Andrew

[1976CamaroGuy]

Thanks, I'm going through and checking everything. I checked for power on the camshaft position sensor plug and I have 12v reference on the red wire and low reference on the pink/black wire like I am supposed to...I was under the impression that the camshaft position sensor controls injector pulse so I def wanted to check that plug.

[1976CamaroGuy]

It's ALIVE!

Someone on nastyz28 pointed out my TPS error on my HPtuners scan so I started looking into that

I'm actually kind of embarrassed about this but here is what happened

I had the TPS low reference and 5v reference wires reversed. At some point a few years ago I removed the DBW throttle body set-up and added a PCM capable and cable throttle body set-up.

But to do this I had to add the specific wires to my 2004 harness which included TPS and IAC valve.

During the process I made notes in my 2004 Harness spreadsheet for Pin 8 and Pin 60 on the blue connector for low reference and 5 volts, only difference is I flipped the wire colors.

I actually installed it this way on my harness before I recently modified it, so it's been this way all along. Makes sense now why I was fighting idle and running issues before taking it to the body shop. All I did was labeled the wires based on my old pin outs and re-installed them the same way on this one.

I went to eficonnections website and looked at their info on the TPS pigtail and compared it to my spreadsheet, the colors were backwards. I pulled a unmodified 2004 GTO pin out list and sure enough it didn't match what I had.

Went and looked at my PCM connectors and I did in fact have them backwards, moved them to the correct spot.

Engine fired right up and didn't miss a lick

[andrewb70]

Glad you have it figured out. This could have been a lot more complicated!

Andrew

[1976CamaroGuy]

Yeah no doubt, the one thing about having issues like this is that it forces you to learn these EFI systems a little more. I take away more understanding on what each component does and why it does certain functions. Def a learning experience