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Fuel injector..timing..electronics..accelerator to keep running…

Customer Question
my 305 engine wont run...
my 305 engine wont run changed egi, computer, fuel injector per code check also reset distibutor timing and checked all electronics per book all was good have to pump accelerator to keep running but backfires what else do i check
Submitted: 8 years ago.Category: GM
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Answered in 2 minutes by:
6/29/2010
GM Mechanic: Danny, GMC Technician replied 8 years ago
Danny
Danny, GMC Technician
Category: GM
Satisfied Customers: 5,064
Experience: Fleet mech with gmc vehicles as our primary service auto's
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Is your convertor clogged?
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Customer reply replied 8 years ago

are you meaning catalytic converters they are recent installed

GM Mechanic: Danny, GMC Technician replied 8 years ago
do you hear a clicking sound at the thottle body. I am sure you have checked your rotor and cap for carbon cracks.
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Customer reply replied 8 years ago
no clicking sounds checked cap , everthing under distributor cap is new what is square electronic device attached to map we could not check this device
GM Mechanic: Danny, GMC Technician replied 8 years ago

http://www.mediafire.com/?mgiy1johwjd

 

 

IAC Valve Operation And Fuel Pressure Regulation


The Throttle Body Injector (TBI) unit is made up of two major castings: a throttle body and a fuel body. The throttle body contains an Idle Air Control (IAC) valve to control idle air flow and a throttle position sensor mounted on the throttle valve shaft. The fuel body contains a fuel meter cover with an integral fuel pressure regulator to maintain constant fuel pressure and an injector on 4 cylinder models or injectors on V6 and V8 models.

The throttle body portion of the TBI may also contain several ports located above or below the throttle valve(s) to provide vacuum signals to various vacuum operated equipment.

Each fuel injector is a solenoid operated device controlled by the ECM. Incoming fuel is directed towards the lower end of the injector assembly, Fig. 2. When the ECM actuates the injector solenoid, the normally closed ball valve is lifted off its seat and pressurized fuel is injected in a conical spray pattern at the TBI bore wall(s) above the throttle valve(s). Excess fuel is routed through the pressure regulator before being returned to the fuel tank.

The fuel pressure regulator is integral with the TBI fuel meter cover and is serviced as an assembly with the meter cover only.

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GM Mechanic: Danny, GMC Technician replied 8 years ago
graphic

Edited by Danny on 6/29/2010 at 6:36 PM EST
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GM Mechanic: Danny, GMC Technician replied 8 years ago

this is testing for map sensor.

 

 

http://www.mediafire.com/?mgiy1johwjd

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Customer reply replied 8 years ago
what in your opinion causes backfire and wont run without pumping accelerator
GM Mechanic: Danny, GMC Technician replied 8 years ago
what do the plugs look like? You may need a throttle body or the valves may be damaged
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Customer reply replied 8 years ago

plugs looked running lean changed out with new ones. throttle body sensor or what how could valves be damaged

GM Mechanic: Danny, GMC Technician replied 8 years ago
Unless you have replaced or rebuilt the engine lately its a 23 year engine. replace the fuel filter if you havent and also the fuel pressure reg.

Edited by Danny on 6/29/2010 at 9:28 PM EST
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GM Mechanic: Danny, GMC Technician replied 8 years ago
If its a tinny back fire its lean on gas it its smokeing popping back fire is difference.
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Customer reply replied 8 years ago
i need to talk to mechanic again to make sure i asked everthing
Customer reply replied 8 years ago
could this problem be cracked cam shaft or bad timing chain
GM Mechanic: Danny, GMC Technician replied 8 years ago
I dont believe so at all. Some vehicles in the late 80s used a spark control module. That would be on the right side of the TBI unit, mounted on a bracket. Some have a ignition control module in the distrbutor make sure a new one was replaced if yours called for it. I know you said you replaced the distrbutor already.
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