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97 Chevy: 350 Vortec..throttle body..starts right..runs good

Customer Question

97 Chevy Silverado - 350 Vortec - multi port fuel injected. It gets no fuel on startup. If you pour gas in the throttle body it starts right up and runs good with good throttle response. A new fuel pressure regulator was put in and pump is running good. Haven't pressure tested it yet but sounds good. Any thoughts?
Submitted: 11 years ago.
Category: Car
Expert:  Steve replied 11 years ago.
Sounds like an unusual problem!   Anything that would normally affect a fuel system to cause starting problems should also cause driveability problems like hesitation, etc...
   One possibility might be a faulty throttle position sensor or a short to voltage in the throttle position sensor circuit.   A TPS should normally show about 1 volt, possibly slightly less, on teh signal return wire of the circuit. If a throttle position sensor is sending back a high voltage, in teh vicinity of 4 volts, the computer will enter "clear flood" mode, where it shuts off fuel pulse during crankling to allow a flooded engine to clear.    If you have a scan tool you can easily monitor this; if not, you can check for this condition by backprobing teh TPS signal circuit at the rear of the powertrain controller plug and monitoring voltage with a high impedance DVOM during cranking.
   if anything else occurs to me, I'll let you know!
Expert:  Steve replied 11 years ago.
I've done a little research on this problem, and found GM service bulletin #99066F which very closely matches your symptoms.
   Apparently, these engines had some problems with deposits forming and clogging the poppet type fuel injectors used on this engine, causing (among other symptoms) hard starting from lack of fuel.   While most solvents will not remove these, GM has come out with a solvent and service procedure to clean the injectors to resolve the problem.   The best part is they have issued a warranty for 200,000 miles regardless of ownership for this condition.   (the warranty coverage probably does not cover diagnostic labor to verify the condition; you may need to pay for this yourself).    
   I would suggest calling your local GM dealer, mentioning the TSB and your symptoms, and give them the VIN number of your truck. They can quickly and easily check their system to see if this procedure and warranty coverage pplies to your vehicle, and make arrangements to resolve the issue for you.
Hope this helps!
Customer: replied 11 years ago.
Reply to Steve Rapp's Post: I will try this within the following week - sorry about the delay. If this is the problem I will pay the fee.

Thanks!!
Expert:  Davo replied 11 years ago.
 I suggest you check the fuel pressure if it is even 5 psi low that engine will not start without adding fuel as you have described.The bulletin that was addressed by Steve will only apply if you live in California and bought the truck there it also only addresses a hard start,misfire,rough idle or a service engine soon light NOT a no start.You have not mentioned any of those symptoms only a no start condition where you have to add fuel to start the engine.You will find a new fuel pump will correct the problem.When you change the pump you must also change the wiring pigtail at the pump.Failure to do so will cause a repeat fuel pump failure about 6 months from now give or take a little.You need to make sure that you installed the proper regulator also there are several calibrations for those trucks.I would suggest replacing the fuel filter while you are at it.The spec for the fuel pressure is 60-66 psi key on engine off if its down to 55 psi it is not enough and it will not start properly.Cycle the key several times to get the correct reading,do it in the morning if possible before the engine is warm.I have seen this problem many times in my shop.If this helps you please click on my ACCEPT button.Thank you for choosing Just Answer.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: My son is out of town until Friday - I will have him check it then. Thanks for the help - I will pay as soon as he finds out if this solves the issue.

Thanks again,
CAT

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