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GMC Sierra Hard Starting, Flooding

Q. Hi Vincent, I recently purchased a 2000 GMC Sierra. About two weeks ago I began to notice that it was starting rough. After firing up there was a vibration for a few seconds, like it had been partially flooded. Occasionally it doesn't fire up on the first attempt and I have to try it again with the accelerator pressed a tiny bit.

GMC Sierra Hard Starting, Flooding

It then fires up but again shakes as though it's flooded. It always starts and seems to do this in no definite pattern. Sometimes it happens when the engine is cold and sometimes when it is hot. Now even when it does start right away it behaves as though it has got too much gas for a few seconds.

It runs fine after this and generates normal power and has normal fuel economy for the engine. Any suggestions as to what the cause might be? Perhaps there are many possibilities? I know that the truck did not do this before as it previously belonged to my Dad.

  • 2000 GMC Sierra (Ext Cab)
  • 5.3 Liter
  • Automatic
  • 42000 miles
  • Fuel Injected
  • ABS
  • P/S, A/C, Cruise control

Thanks for any help you can give,


There is a 95% chance that the fuel pressure regulator is leaking. It's mounted on the fuel rail on the drivers side of engine. There is a vacuum line that goes to it. If you were to pull this vacuum line off with the engine not running, you will probably see some gas drip out. If so, it's bad.

GMC Sierra Hard Starting, Flooding

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