I have had issues with negative fuel trims for quite sometime. I thought negative fuel trims meant the system was running rich, but it actually means the system is running rich and the computer then tries to compensate by removing fuel.

In the last few months, the truck has thrown a rich code a few times but that is after several hundred miles. Ive also read that since one leaky injector richens one cylinder, the computer pulls fuel from the entire engine, causing the other cylinder to go lean, which can cause a misfire in one lean cylinder. I recently had one plug broken and misfire.

At idle, the fuel trims begin around -3% and can slowly work themselves up to -17%. I finally got a wideband installed and working today and it appears that WOT is 12.0-12.5AFR and cruising is 14.0-14.5 AFR.

After some reading, it seems all these issues point towards a leaky or drippy injector. How can I find out if that is the problem? 2000 S10 4.3

 

You need to isolate the fuel rail...the way that I've always checked for leaky injectors (on different manufacturers), is to hook up a fuel pressure gauge to the fuel rail, fire up the fuel pump to get pressure up, then clamp off the feed and return lines to the fuel rail and observe the gauge. With pressure built up, and both lines clamped off, the fuel rail should maintain pressure. If pressure drops, it is doing so in the form of a leaky injector

 

could also just take your rail off your intake with the injectors still clipped in the rail and power up and see if one leaks.

 

what happend to the plug, how did it break? from you or while running? was this on a nitrous run?

 

Might want to have a back up set of o-rings for when the rail goes back together to insure that there aren't any leaks

 

never seen an o-ring fail, Ive always re-used o-rings. been a while since ive messed with stock rails, dont they have a clip holding them in like the ls1 rail does?

 

IIRC, there's a clip that holds the injector into the rail, so when you pull the rail up, the injectors should stay attached like you mentioned. I've seen o-rings go bad once re-used, but then again I've also seen them re-used without problem...it's kinda hit or miss.

 

For the pressure to drop all the way from 60 psi to 5 within 5 seconds with key on engine off, could that be a leaky injector dropping that much fuel into the cylinder?

 

More than likely if that is the only symptom you have coupled with a "slow" starting engine, your fuel pump check valve is shot.