I just recently added a Vortec VS-2 to my '99GT. Got it tuned up at NEDyno and ran 353rwhp - all was well (other signifcant mods are Magnaflow X-pipe and cat backs, Accufab TB 70mm TB and plenum). Injectors are 30#.
After a week the following started to happen.
After 5 minutes of driving at about 3-4rpm I lose fuel pressure. I ran a data logger and watched the fuel pump duty cycle as well as FP. 4K is when it starts to build any decent boost so I didn't even push it. The dying process happens in less than 2 seconds.
Nominally it was running about 40psi and 22% duty cycle on the pump. When it lost pressure, PSI dropped below 20 and duty cycle picked up to 50% and stayed there.
It would crank fine. I can hear the fuel pump re-pressurizing the system each time I turn the key on (there's a subtle clunk from the rear).
After an hour of sitting she fired back up just fine and I drove it back home. On the way home, I took it up past 4K and it immediately spluttered and nearly died out.
The FP came with the Vortec kit, it's a 255Lph Walbro which Vortec indicate they have had no issues with it. They tell me the problem is with the tune yet it ran fine on the dyno over 12 runs.
One specific question - why didn't the pump go over 50% duty cycle?
One major thing - when I replaced the fuel pump, I damaged the seal where the filler pipe enters the tank - it leaks - a lot !. I'm going to fix that this weekend but could I have damaged any venting? Could the tank be building a negative pressure thus preventing any more gas no matter how hard the pump tries?
Thanks for any insight.
After a week the following started to happen.
After 5 minutes of driving at about 3-4rpm I lose fuel pressure. I ran a data logger and watched the fuel pump duty cycle as well as FP. 4K is when it starts to build any decent boost so I didn't even push it. The dying process happens in less than 2 seconds.
Nominally it was running about 40psi and 22% duty cycle on the pump. When it lost pressure, PSI dropped below 20 and duty cycle picked up to 50% and stayed there.
It would crank fine. I can hear the fuel pump re-pressurizing the system each time I turn the key on (there's a subtle clunk from the rear).
After an hour of sitting she fired back up just fine and I drove it back home. On the way home, I took it up past 4K and it immediately spluttered and nearly died out.
The FP came with the Vortec kit, it's a 255Lph Walbro which Vortec indicate they have had no issues with it. They tell me the problem is with the tune yet it ran fine on the dyno over 12 runs.
One specific question - why didn't the pump go over 50% duty cycle?
One major thing - when I replaced the fuel pump, I damaged the seal where the filler pipe enters the tank - it leaks - a lot !. I'm going to fix that this weekend but could I have damaged any venting? Could the tank be building a negative pressure thus preventing any more gas no matter how hard the pump tries?
Thanks for any insight.
