1999 GMC Truck, Hard to Start when engine warm?

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engines
gmc

#1

Auto tech told me, that my fuel pump had low pressere 40 psi. Install new oem fuel

pump, new NGK sparkplugs, new fuel pump.

Same old thing…Starts fast, when cold,starts slow when warm…same as before, What’s Next? (5.3 liter engine).


#2

What’s Next?


#3

Are there any CEL error codes? Has the spark been checked? What is the fuel pressure numbers now? How come I don’t see a new fuel filter on the list?

OK I suspect a sensor.


#4

When the fuel pump was replaced with a oem new fuel pump, we also installed a new fuel filter (old filter
pretty dirty), and also replaced plug with NGK platium tip plugs. No check engine light. The truck
starts fine when cold, but hard to start after driving for a somewhat short period of time. Same as
before we did all the above. The reason I changed the fuel pump was, that a mechanic checked the fuel
pressure…pressure was low, about 40 psi. Also, last winter, and the winter before that, when real cold
I would get a couple of check engine codes: P0430 X2 on bank 2, and P0 171-Bank 1, and p) 174 Bank.
After the weather warmed up again…light would go off. No check engine light has ever come on again?


#5

When the fuel pump was replaced was the connector replaced as well? GM had a problem from 96-03 with a voltage drop through the fuel pump connector resulting in low fuel pressure. Also have you spoken to GM about this problem? There was a TSB issued involving your truck that recommended a flash of the ECM to cure a lean condition during hot restart. I have attached the TSB that has the proper ECM calibration numbers. Your local GM dealer should be able to tell you if the update has been done or should be done from the vin#. Hope it helps.
~Michael