2004 lb7 running diablosport predator on highest tune. Around 3000psi at idle 5000-10000 cruising around and doesn't go over 17000 at WOT. On stock injectors at 260k but balance rates are within 3+- and it doesn't haze. Could it just be this tuner? Maybe change the fuel filter or fpr?
LB7: Fuel rail pressure low at WOT
- Thread starter tyler.frost92
- Start date
Injector return rates can be through the roof and still have balance rates all +or- 2, I've had multiple customer trucks like this... Especially if you are saying you have 260k miles on the original injectors.
Pull the banjo bolts from the return lines from each head and from the cp3 and from the fuel rail relief valve and run them into separate containers
You can also pull the return line off from the engine going to the tank and run it into a can. Crank the engine for 15 seconds with the FICM unplugged and measure how much fuel is returned. GM spec for the whole engine is 3.5 onces I believe, but that is way to much to allow it to hold rail with any sort of tune. I deally you want less than 2 onces for the whole engine. If you get more fuel out, then take the return line off from the CP3 and recheck to see if the CP3 or injectors is returning the excess fuel.
To your original question, YES.
If your fuel pressure was actually that low at WOT, I'm thinking you'd be popping codes and triggering limp mode. If it's not limping, I'm guessing it's feeding ya BS data. Some tuners or add on boxes used trickery to jack the pressure. I know the Quadzilla I tested on a Ford did, but have no experience with the Diablo on the Duramax.
First I'd put it back to stock and check it again at WOT. If it's a true fueling issue it will still be there. Ultimately you need to compare the requested fuel pressure to actual fuel pressure pids with a decent scanner. They should track within 1000lbs all the way up the scale.