Injectors Not Firing

[jakebdb56]

I went yesterday to tune a truck that my buddy did a motor swap in and we're having a little issue that I can't put my finger on. Here's the setup:

2004 V6 Silverado
Swapped to a LQ4/L92 setup
Throttle body works just fine
SVO Green Top injectors
4L80E Segment swap on V8 OS

Basically what's happening is injectors 2/4/5 aren't doing anything. I know the injectors are fine, and the stock L92 injectors did the same thing before I swapped them for 42's that I know work. I checked the injector clips and they're all soldered really well and the leads have continuity all the way to the PCM connectors. They're also getting a good switched 12v power to the connector. With the motor idling (like shit) you can just unplug those injector clips and it doesn't effect the motor. If you unplug the ones that are firing 1/3/7/6/8 it'll make the motor stumble and die. I haven't used a noid light, but using the multimeter I'm not getting a ground pulse to the clips that aren't working but I am getting a pulse to the ones that are working.

I figured okay maybe it's just a bad PCM so I hooked up a spare one I had and did a write entire with the tune file. Same problem with the same cylinders. Is it possible that the OS could be corrupt and not telling the injectors to fire?

The V8 base file that I got segment swapped was from another customer's truck that was a 2004 V8 etc.

I don't have my laptop with me, but I will post the tune file later.

Also, one thing that's strange is the gas gauge shows exactly the opposite of what's in the tank. Full tank shows empty on gauge, empty tank shows full on gauge. Never had that problem on my buddy's 2006 V6 truck that we put an LS2 into. Maybe that's a sign that something is up?

Thanks for reading my novel lol, just need some ideas on how to trace/diagnose this problem.

[jakebdb56]

This is the file that I started from, I don't have the one with all the correct fueling changes or anything in this file since it's on my laptop across town.

[RMS-Man]

I've had SVO Injectors that didn't want to fire after sitting on the shelf for a while. This happened on 2 different vehicles. While the car was running like crap I started banging on metal body of each injector with a big wrench and they started firing again. Never had anymore trouble out of them.

I used a mechanics stethoscope to listen to each injector and you could tell they were not firing.

[Google]

I went yesterday to tune a truck that my buddy did a motor swap in and we're having a little issue that I can't put my finger on. Here's the setup:

2004 V6 Silverado
Swapped to a LQ4/L92 setup
Throttle body works just fine
SVO Green Top injectors
4L80E Segment swap on V8 OS

Basically what's happening is injectors 2/4/5 aren't doing anything. I know the injectors are fine, and the stock L92 injectors did the same thing before I swapped them for 42's that I know work. I checked the injector clips and they're all soldered really well and the leads have continuity all the way to the PCM connectors. They're also getting a good switched 12v power to the connector. With the motor idling (like shit) you can just unplug those injector clips and it doesn't effect the motor. If you unplug the ones that are firing 1/3/7/6/8 it'll make the motor stumble and die. I haven't used a noid light, but using the multimeter I'm not getting a ground pulse to the clips that aren't working but I am getting a pulse to the ones that are working.

I figured okay maybe it's just a bad PCM so I hooked up a spare one I had and did a write entire with the tune file. Same problem with the same cylinders. Is it possible that the OS could be corrupt and not telling the injectors to fire?

The V8 base file that I got segment swapped was from another customer's truck that was a 2004 V8 etc.

I don't have my laptop with me, but I will post the tune file later.

Also, one thing that's strange is the gas gauge shows exactly the opposite of what's in the tank. Full tank shows empty on gauge, empty tank shows full on gauge. Never had that problem on my buddy's 2006 V6 truck that we put an LS2 into. Maybe that's a sign that something is up?

Thanks for reading my novel lol, just need some ideas on how to trace/diagnose this problem.

Just wondering if you have tried to load a different tune into it and see if the injectors fire? Would help you eleminate the tune as the problem. I know that the injector bank 1 has a different power supply then bank 2 so if your not firing on 2/4/5 then power is out. Maybe one bad ground at the pcm of the 4 grounds. I have seen it mess with functions before like this when a ground is missing from the pcm.


Just something else to try n help you rule out things.

[69lt1bird]

I haven't used a noid light, but using the multimeter I'm not getting a ground pulse to the clips that aren't working but I am getting a pulse to the ones that are working.

Check continuity of the wires from the PCM to the injector connector.

They are in Connector 1 (C1) BLUE

Pin 4 = injector 2 ground
Pin 44 = injector 4 ground
Pin 76 = injector 5 ground

[jakebdb56]

Just wondering if you have tried to load a different tune into it and see if the injectors fire? Would help you eleminate the tune as the problem. I know that the injector bank 1 has a different power supply then bank 2 so if your not firing on 2/4/5 then power is out. Maybe one bad ground at the pcm of the 4 grounds. I have seen it mess with functions before like this when a ground is missing from the pcm.


Just something else to try n help you rule out things.

Yeah that's actually what I ended up trying last night, no luck. I'm beginning to think that it's a ground issue since all the wires in question have continuity and the injectors have the correct switched 12v. We did find out that it's a compound no fuel no spark for the cylinders. 2/4/5 no injector firing, but 4 doesn't have spark either. I'm having Zach look over the harness today and check all the grounds. Might just jump the grounds over at the buss center to a chassis ground or just directly to the battery to rule that out. I'm really hoping we can get it figured out tonight because it's starting to get frustrating lol.

Check continuity of the wires from the PCM to the injector connector.

They are in Connector 1 (C1) BLUE

Pin 4 = injector 2 ground
Pin 44 = injector 4 ground
Pin 76 = injector 5 ground

Yeah that's the first thing I checked after checking for switched power. I'm leaning towards the grounds to the PCM not being good because a bad ground could be screwing up both the injector and coil ground signals.

Thanks for yall's input, its nice having more than two brains thinking about it

[jakebdb56]

Haven't had a chance to test the grounds yet, but another odd thing I noticed was that before I stopped working on it I had the MAF set to fail but it wouldn't throw a MAF code (all are mil on first). Kinda weird I thought.

[NoGamesLS1]

Have you tried a node light tester?

[jakebdb56]

Have you tried a node light tester?

Haven't used a noid light, but I've used my multimeter and it picks up pulse on the cylinders firing the injectors but not on the ones not firing. As for the spark, we're using a timing light to test for it.

[NoGamesLS1]

A couple months ago I started getting a miss. I found that the rear 4 cylinders (5-8) were not firing or firing intermittently by feeling the primaries. This is what I did as far as troubleshooting:

1) Pull plug and checked for spark. Hooked up plug to all coil packs to make sure it fires. All coils have spark.
2) Replaced plugs on non-firing cylinders.
3) Swapped non-firing cylinder injectors with firing cylinder injectors
4) Swapped plug wires.
5) Swapped coil packs from ds->ps
6) Swapped PCM
7)Node light
8)Check pressure at the rail
9)Changed plugs

When I unplugged the front 4 injector the rear four would fire. It was the strangest thing. I spent almost 2 weeks trying to figure it out until one day they all fired up. I searched over several forums and could find anything. I know this probably isn't helping you a lot, but I feel you pain and frustration. I will keep this in the back of my head.

[MM Alexander]

A couple months ago I started getting a miss. I found that the rear 4 cylinders (5-8) were not firing or firing intermittently by feeling the primaries. This is what I did as far as troubleshooting:

I literally just joined this forum because of this thread. I'm having the EXACT same problem with my 06 GTO.
As I was driving home from work a few weeks back (cruising in 6th gear at 65 on 45 heading south) my car starts to vibrate. I initially thought it was the tires/road (maybe a blow out).
I continue on another mile or so and speed up (raise rpms above 2400 and it smooths out slightly) in order to try and exit.
Get off the free way and pop the hood. The car is shaking pretty hard and missing but no check engine light at this point. I look over the motor and nothing obvious (Harmonic balancer still in tact, no loud knocks or pings). I decided to chance it making it home (figure the worst it could do is stop and I'm stuck waiting on road side assistance to arrive). Make it to my Dads and I break out a few tools to diagnose.
I started disconnecting coils one by one and find the back four cylinders (last 2 on either side of the motor) are not firing. I pull the plugs and they don't look abnormal.
Suspecting I could have broken springs (Comp 918's ) I pull the valve covers ... No issue to be found all looks fine.
I decide to swap the coils around on re-assembly (to see if the coils themselves failed ... which would be strange for all 4 to fail at once but you never know). Nope, no change there, still not firing on 5-6-7-8.
I limp it home on 4 cylinders and park it in the garage for the night (right next to my Turbocharged Mustang that grenade'd it's motor less than two weeks ago .... FML at this point ).
I figure it could be electrical (though all the coils have power on them) or a bad sensor of some sort.
I took the following day off to look over the car further. Tested all the coils, swapped around plugs and wires, tested for power to the injectors (could only test the positive since I didn't have a noid light handy ... I'll make one when I get home). Nothing wrong on any of that, still no understanding/meaning for the lack of combustion on 5,6,7,8. I've scoured the entire car schematics and there really isn't a whole lot involved in the powering of the injectors coils. A pair of power wires for coils and injectors (4 per wire/fuse) which both are in fine. I'm wondering if the injectors (though it's weird for it only to be the back injectors) are clogged because if I let it run, the 4 cylinders with no fire don't have wet plugs (from unburned gas). Weird as I know for a fact that the cylinders are not completing the combustion process (header primaries for those cylinders are cold ... literally no heat on them for about 5 -10 minutes until the radiant heat from the other primaries starts to spread).
Going to pull the covers again, let it run with them off and see if the cam hasn't cracked.

When I unplugged the front 4 injector the rear four would fire. It was the strangest thing.

I haven't done that (never crossed my mind to try) but I will next week (working in Oklahoma until then).

I spent almost 2 weeks trying to figure it out until one day they all fired up. I searched over several forums and could find anything. I know this probably isn't helping you a lot, but I feel you pain and frustration. I will keep this in the back of my head.

Well, I only got like a day and a few hours into the troubleshooting before I had to jump on a plane. I plan to spend the Turkey Holiday looking for the problem (noid light will be in hand). I've perused various search engines with different worded quarries in search of similar issues (which is how I found this posting).
I hope and answer or some that PFM that you experienced happens for me. At this point I'm

[Google]

sounds like a crank or cam sensor problem.

[MM Alexander]

sounds like a crank or cam sensor problem.

Wouldn't that (either one) cause a total "no fire" issue as opposed to it simply being the back 4?
Also, wouldn't those trip the MIL?
Could you elaborate on either a bit further?

[Google]

Wouldn't that (either one) cause a total "no fire" issue as opposed to it simply being the back 4?
Also, wouldn't those trip the MIL?
Could you elaborate on either a bit further?

injectors power is supplied to each bank eg; two different fuses. not back 4 and front 4. pcm supplies a ground to fire the injector via a driver in the pcm. so if your getting power to bank 1 cyl 1,3, then you have to be getting power to cyl. 5, and 7 unless you have a short very close to the injectors them self.. with in 6" or so.. you said you have checked all the wiring. now if the pcm is not getting 1 of the 4 pcm grounds assuming it is an 0411 pcm, then it will cause this problem.. but again you said you checked the wiring..

so the only other thing to tell the injectors to fire would be cam/crank sensor. if the cam sensor is not picking up a full pulse or not sending the pulse correct then it could cause a not start and or a start but not all cyl's to work correct.

last option would be a bad pcm, as I have not seen one just go out on it's own without a short to ground.. I doubt it is the pcm.

[MM Alexander]

injectors power is supplied to each bank eg; two different fuses. not back 4 and front 4. pcm supplies a ground to fire the injector via a driver in the pcm. so if your getting power to bank 1 cyl 1,3, then you have to be getting power to cyl. 5, and 7 unless you have a short very close to the injectors them self.. with in 6" or so.. you said you have checked all the wiring.

I fully understand the wiring. The coils & injectors for 2,4,6,8 are powered by Red > Pink for injectors ( S154 )
Red to coils ( S137 )
1,3,5,7 are powered by Lt. Grn > Pink for injectors (S155)
Lt. Grn to coils ( S138 )
I covered all those (and associated fuses) thoroughly. I didn't have a noid light nor did I have any LED's (to make one in a pinch) but I will once I return back home.

now if the pcm is not getting 1 of the 4 pcm grounds assuming it is an 0411 pcm, then it will cause this problem.. but again you said you checked the wiring..

Yeah, I'm leaning towards the negative from the computer not being supplied (again no noid light so I didn't check the pulse to the injectors).

so the only other thing to tell the injectors to fire would be cam/crank sensor. if the cam sensor is not picking up a full pulse or not sending the pulse correct then it could cause a not start and or a start but not all cyl's to work correct.

That's what I was asking for clarity on (not the wiring itself ... though I will assume you were trying to be helpful ... the repetitive "you said you checked the wiring" did seem a bit condescending) .
I've only dealt with crank/cam sensors once, on a Mercedes I owned a year or so back. When it went, the car would not fire at all. I guess I'll have to add checking the cam sensor to the list.

last option would be a bad pcm, as I have not seen one just go out on it's own without a short to ground.. I doubt it is the pcm.

I concur, I've rarely seen a PCM die in normal operation (save for quite a few late 80's early 90's Buicks ... Those crappy arse things had bad boards and would cut on and off over bumps).
Thanks for the help.
I'm now going to look up the testing procedure for the cam sensor in these cars.

[Google]

no, I was not tring to be an A$$. just hinting that it is prolly wiring.. lol I have seen alot of gound problems on the rear of the cyl head after cold weather and the aluminum shrinking more then in the summer. But it could be a cam-crank sensor problem as well. Hope you find the problem though!

[jakebdb56]

Sorry I hadn't posted on here lately.

Well, we've done everything pretty much to solve the issue besides changing cam sensors.

The only problem we have right now is Cylinder 6 (or 8, can't recall exactly right now) isn't getting spark no matter what we do. The wiring is fine and all wires have continuity. All of the injectors are firing correctly, but just no damn spark on one cylinder.

I tested the injector deal using another injector and plugging it into the harness and making sure it clicks. We're using a timing light to test for spark, and the plug is definitely wet from fuel just no spark.

We replaced the harness, crank sensor, 3 PCM's, 5 different OS's, 3 sets of coil packs, 2 sets of injectors, and even jumpered the grounds for the PCM to the battery.

So could a cam sensor actually cause just one cylinder not to spark?

Also, we dropped the pan to make sure the reluctor on the crank was fine too and it's ok.

Any insight would be great because we're at a loss right now. It kinda drives you to consuming beverages after a while lol

[Google]

Sorry I hadn't posted on here lately.

Well, we've done everything pretty much to solve the issue besides changing cam sensors.

The only problem we have right now is Cylinder 6 (or 8, can't recall exactly right now) isn't getting spark no matter what we do. The wiring is fine and all wires have continuity. All of the injectors are firing correctly, but just no damn spark on one cylinder.

I tested the injector deal using another injector and plugging it into the harness and making sure it clicks. We're using a timing light to test for spark, and the plug is definitely wet from fuel just no spark.

We replaced the harness, crank sensor, 3 PCM's, 5 different OS's, 3 sets of coil packs, 2 sets of injectors, and even jumpered the grounds for the PCM to the battery.

So could a cam sensor actually cause just one cylinder not to spark?

Also, we dropped the pan to make sure the reluctor on the crank was fine too and it's ok.

Any insight would be great because we're at a loss right now. It kinda drives you to consuming beverages after a while lol

can you hook a volt meter up to the pcm ground signal wire for that coil and see if the pcm is sending the ground to fire the coil?

have you tryed changing the one spark plug as the plug will not spark if it is shorting to the head and not the electrode and this could give a false negitive on your test light? same for the spark plug wire.. odd but it could be the problem.

[jakebdb56]

Yeah that's the only cylinder that doesn't get a ground pulse although the pulse wire is continuous to the PCM without loss of signal. I would have loved to find a chewed up wire amongst all of this, that would have been too easy.

We tried swapping plugs, wires, and coils and no improvement. He went ahead and put new MSD wires on it to be safe.

One thing that's odd is the primaries of 6 and 8 are red hot at idle. I remember now that the no spark issue is only on cylinder 4 because I remember the 6 and 8 red primary deal being really weird. They're stainless headers and was easy to see at night. All other are fine.

[Google]

red hot meens it has to much resistance in the wire and or bad ground and it is drawing from the + side. also could be a short to a + on the power side and different item is tring to draw the power from the coil.