LB7 - P0193 (Fuel Rail Pressure Low during Power Enrichment)
Texas Diesel Company has the factory GM computer in-house! This allows us to quickly and effectively diagnose your vehicle saving you both time and money. We are also able to provide in-house programming of all components & modules installed in your vehicle, no different than the Chevrolet/GMC dealership would. If you’re another local shop interested in having us re-program a module for you, please call (903) 292-0400
The primary cause for this issue is typically a fuel system issue. First you want to check if the fuel filter has been replaced recently. If this information is not available, it might be a good idea to go ahead and replace it. Don’t forget to re-prime the system using the plunger on top of fuel filter housing, this will take quite a few pumps. Do this until the plunger gets stiff and
then try to re-start. You may have to complete the sequence 3 or 4 times before the system is fully primed.
If this doesn’t fix your problem, hook a vacuum gauge to the service fitting and check the vacuum. You should expect to see less than 5” of vacuum at wide open throttle position in park. If you have an issue where your actual fuel rail pressure is higher than the desired, it may be time to replace your fuel pressure regulator. If your actual fuel rail pressure is lower than desired, it would be best to suspect a fault somewhere in your high-pressure fuel system.
From this point, we recommend doing an external visual inspection. If there are no visual leaks, try removing the relief valve line and make sure that it isn’t hanging open allowing all your fuel pressure to escape the rail. If you find nothing there remove both valve covers and re-install your high pressure fuel lines to check for any visible leaks while cranking. Make sure to wear eye protection while doing this. At this point if the vehicle is not running it is best to suspect either a bad high-pressure pump (not as likely) or a bad set of injectors (likely). LB7 injectors are notorious for going out in a set, in-fact GM issued a recall for all LB7 models to have all their injectors replaced, under warranty, just a few years after their production.