got a good one....HARD START

[texpert]

97 yukon 5.7l


problem :hard start

symptons:

1. will start with short cranks only (turn the key for half a second).
2. now thats its cooler in the mornings, here in ny, its starts quicker, otherwise later in the day when it warms up outside it wont start right away. sometimes i kill the battery trying to start it, after i throw the jumper cables on them it starts up after a few minutes (with short cranks).
3. DEFINITELY will not start at all with normal key turning (just kills the battery).
4. once my car is running, i do get a little hesitation while accelerating ( if i punch it) i accelerate fine when its a soft push on the gas pedal.
5. i put two cans of injector cleaner on a recent fill-up. drove about 40 miles didnt seem to help.next day worked perfect. two weeks later problem came up again almost instantly after i jumped my battery.

I REPLACED THE DISTRIBUTOR CAP, PLUGS, ROTOR, FUEL FILTER AND STARTER. NO FIX!


I HAVE A FEELING IT COULD BE O2 SENSORS AND/OR BAD BATTERY CABLES, WHAT DO YOU GUYS THINK COULD BE THE PROBLEM?

[2000CAYukon]

You need to test the fuel pressure to make sure it is in range. Should be 55-60 at idle. Also, if you shut the engine off, the pressure should not drop very fast.

The Fuel Pressure Regulator is a common part to fail on these engine causing hard starts, especially after an hour or two of sitting.

//2000CAYukon

[borchelt]

Good thought around the battery cables. Usually the ground side. I'd replace it.

[94 Jimmy]

Good to check the fuel pressure, but if it were low it wouldn't start cold either. It sounds like it's flooding, possibly because it's getting bad O2 snsor readings. When it's warm try pressing the accelerator all the way to the floor while cranking. This tells the computer to shut off all of the injectors to clear a flood. Without additional the air entering the combustion chamber should clear the flood rapidly.
Do you have a rotton egg or burned hair smell from the exhaust? This is an indication of a rich mixture being burned in the catalytic converter.
I had a similar problem when my O2 sensor drifted to a rich reading. The computer dutifully leaned the mixture so when I was sitting at a stop light the engine would sputter and die. No codes, no nothing, the computer thought it was doing the right thing. The problem had to progress until the computer noted that the sensor was not transitioning between a rich and lean reading often enough.
The O2 sensors only work on a warm engine, the computer uses stored readings to start when cold and if the sensor was reading lean it would richen up the mixture as the sensors come on line.
You can go to www.scantool.net and pick up an OBDII decoder which will read out all of your sensor readings on a laptop or PC.
Good luck
94