01 vilverado 5.3, it used to fire up instanly upon turning the key over. Now sometimes I have to try and start it two or three times and when it does start it doesn't "fire" right up like it used to. It almost feels like it is starving for fuel. Once it is running it is fine and it seems to do it more in the morning when it is cold- well sort of cold I live in Phoenix. Fuel pressure reads fine at fuel rail. Any suggestions???

 

Winter blend fuel contains more Ethanol which can cause extended cranking times.

Unplug the vacuum hose at the fuel pressure regulator and see if any fuel drips out, or better yet if you have a vacuum test pump see if it holds constant vacuum.

Could also be dirty injectors or carbon build-up in the combustion chamber.

Spark plugs could need replaced.

Check high tension plug wires, if any read over 30,000ohm replace the set.

 

starter solenoid possibly

 

Im gonna start with the plugs- question:
Where isthe fuel pressure regulator located, and how do I check the ohms on the plug wires? Thanks bud.

 

The fuel pressure regulator is on top of the driver side of motor on the fuel rail it is a small black round device with a vacuum hose coming out of it, it will have a metal clip secureing it to the fuel rail, it is very easy to check and replace.

To test the spark plug wires use an OHM meter set to "OHM infinity" if it has that setting other wise use the highest ohm setting, remove each wire and connect the red electrode on your meter to one end and the black electrode to the other end, make sure to get a good connection and then read the gauge, if it reads more then 30,000 ohms then make double sure that you got a good connection and if so buy a new set of plug wires. Hint: the plug wires are rarely bad.
Make a good visual inspection of each wire looking for any obvious signs of damage as well.

 

How's the battery?

 

ZX12100F1- I was playing around last night, removed the vacuumm line from the pressure regulator - no fuel dripped outwhether the engine was cold or just turned off. I know that the regulator maintains fuel pressure on the rails but I'm not sure exactly how.
Also I tested the system prime at the fuse box and it is priming as well as I can hear the pump turn onconsistently.
The more I think about it I tend to lean away from the plugs and wires since I have only 48K on the truck and they should be good for at least 100K.
The difficulty is the problem is very intermittent sometimes every day some times not for weeks and once it starts I can shut it off and it fires up immediately on the next turn.
Any other suggestions?

 

Dirty fuel injectors or bad quality gasoline.

The regulator is simple spring loaded diaphram device, the vacuum pulling on one side of the diaphram reduces fuel pressure at idle and other low load operating conditions, when you mash the gas pedal or are under a heavy load manifold vacuum is reduced wich casues a rise in fuel pressure to help assist in supplying extra fuel needed.
If the diaphram is punctured it will allow fuel to be sucked into the engine the engine will run poorly, the regulator has nothing to do with the fuel pump cycling on or off, the pump will cycle for 2 seconds when the key is turned to RUN or START.

 

Since I have heard a lot of people are having similar problems I figured I would fill you in I found it:
Changed plugs, fuel filter, fuel pressure regulator, cleaned injectors - Nothing fixed
Turned out to be the fuel pump- even though it did pump fuel it was not enough pressure so at start up it was taking to long to prime. I replaced it and now it starts just like new!!!
Yipee !!!!!