Injectors are off the truck

[.justin.]

So here's the background. For as long as I've had tuning software now, I've had severe trim differences between the left and right banks, Intermittent stutter at idle, etc. I've exhausted all avenues up to this point and am checking out my injectors (radix supplied). I plan to re-instal them with the odd-cylinder injectors switched with the even-cylinder ones to see if the Trim issues follow.

 

In the mean-time, what obvious signs of issues might I see looking at one? O-ring appears chunked around the base of a few of them, I plan on replacing them. What O-rings do I purchase as a replacement? How do I go about cleaning the injectors while they are off the truck?

[TurbochargedBerserker]

How big were the differences? Where there differences in the O2s as well? Every truck I've seen has minor differences between the banks -- its just normal. I've seen up to 4 points in difference.

 

 

One thing you can do with the injectors out is to check the resistance. They should all be very close together. If you say 7 at 14.5ohms and 1 a 5 ohms, you have a faulty injector.

 

I'd do that before switching sides.

 

Injectors don't really need cleaning off a pressurized flow bench, imo. You can try it with carb cleaner and compressed air, but don't expect much.

[.justin.]

How big were the differences?  Where there differences in the O2s as well?  Every truck I've seen has minor differences between the banks -- its just normal.  I've seen up to 4 points in difference.

 

 

One thing you can do with the injectors out is to check the resistance.  They should all be very close together.  If you say 7 at 14.5ohms and 1 a 5 ohms, you have a faulty injector.

 

I'd do that before switching sides.

 

Injectors don't really need cleaning off a pressurized flow bench, imo.  You can try it with carb cleaner and compressed air, but don't expect much.

<{POST_SNAPBACK}>

10-15% difference in LTFT at low load. When autotuning with the wideband there was a lean condition at 2600rpms decellerating that no amount of fuel adding could fix (DFCO disabled). when I kick into PE mode the pass bank is ALWAYS lower than the drivers bank. sometimes a few mv, sometimes as much as 30mv. Seems a lot like inconsistent flow issues. As a result of that, I can run as rich as 11:1 and still get random KR spikes in the 4-5* range.

 

I'll give the resistance test a try and see what I come up with. Thanks

[mcwarren]

This won't help until you get it back together....... run an injector balance test (not a cylinder balance test) with Tech 2 (measures injector fuel flow by comparing pressure drop). This test will isolate which injector(s) if any are contributing to your concern. I agree with your switching banks since you have the injectors off to see if your fuel trim problem moves with injectors or stays with bank 2.

[.justin.]

This won't help until you get it back together....... run an injector balance test (not a cylinder balance test) with Tech 2 (measures injector fuel flow by comparing pressure drop). This test will isolate which injector(s) if any are contributing to your concern.  I agree with your switching banks since you have the injectors off to see if your fuel trim problem moves with injectors or stays with bank 2.

<{POST_SNAPBACK}>

 

I've read about that recently and inquired with Synergy motorsports if they have a Tech 2 or not. Otherwise I don't have access to one

 

How much would a dealer charge to run that test and how long does the process take?

[mcwarren]

One thing you can do with the injectors out is to check the resistance.

Good point, GM specs on LQ9 injectors are 11 to 14 ohms at 50 to 90 degrees F with no more than 3 ohms difference.

I've read about that recently and inquired with Synergy motorsports if they have a Tech 2 or not. Otherwise I don't have access to one

The Injector balance test can also be ran with a Kent-Moore special tool number J39021 if that helps any.

How much would a dealer charge to run that test and how long does the process take?

My guess is about 1.5 to 2.0 hours labor at whatever the going rate is in your area.

[.justin.]

One thing you can do with the injectors out is to check the resistance.

Good point, GM specs on LQ9 injectors are 11 to 14 ohms at 50 to 90 degrees F with no more than 3 ohms difference.

<{POST_SNAPBACK}>

 

4 injectors sit at 11.7V, the other 4 at 11.8V, so the electronics look good.

 

I've sprayed some seafoam into each of them to soak overnight, will reinstall tomorrow on the opposite bank and see what the results are.

 

[mcwarren]

4 injectors sit at 11.7V, the other 4 at 11.8V, so the electronics look good

 

I agree....if you find that your fuel trim concern moves with your injectors to bank 1 consider having the fuel injector balance test performed.

[TurbochargedBerserker]

And if it doesn't, check your harness, connections, and possibly the PCM.

 

Do you have a fuel pressure gauge?

[.justin.]

And if it doesn't, check your harness, connections, and possibly the PCM.

 

Do you have a fuel pressure gauge?

<{POST_SNAPBACK}>

 

Yep, pressure is good. 62-63psi in boost and doesnt' fluctuate.

 

I've thought of connections as a possible culprit, will definitely inspect all of them as I reassemble everything tonight.

 

thanks

[TurbochargedBerserker]

Well that's a good FP so it must be in the harness or injectors somewhere.

[.justin.]

Well that's a good FP so it must be in the harness or injectors somewhere.

<{POST_SNAPBACK}>

 

That's what I'm hoping If this trim problem moves, I know that injectors are the problem and I can either replace four for $160 or upgrade to larger and replace them all in anticipation of future mods.

[.justin.]

And the injectors are back on and working Man, that was infinitely harder to mount them than to remove them.

 

And it appears that the issue is much better now Idle is smoother, Trims are ALL negative and within 2% of eachother (right now) whereas before, right into Closed Loop, bank 1 would go neg, bank 2 would go positive.

Readings look a bit better in PE mode now as well. Readings between the two banks are a lot closer now, with 8-10mv difference on average.

[04CHASE]

when you pu them back on did you remove your fuel rails? when i did the swap i didnt think to do this until i called erik, made the re-install very easy!

[.justin.]

when you pu them back on did you remove your fuel rails? when i did the swap i didnt think to do this until i called erik, made the re-install very easy!

<{POST_SNAPBACK}>

 

The problem is I had very limited space on the passenger side, due to the radix J-tube. To remove, I unbolted the rail in it's 6 places, lifter it off of the injectors and pulled them out one by one. To remount, I place the injectors all down in the intake manifold and pressed the rails down onto them. Very difficult to press the injectors down into place that were under the J-tube.