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2005 GMC Sierra 1500 Question: my 2005 GMC Sierra V-6 4.3Liter will not crank.Eliminated fuel problem.No fire.

 

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djhyche, Daytona Beach, FL, January 15, 2012, 09:04
 Rookie

I have never had a problem with this truck.Went to the store the other day and when leaving the truck would not start.checked fuel pump and fuel relay.both are in working order.not getting fire to plugs.all the fuses are good.Fuel pressure is good.could my crank relay sensor cause this?Or could plugs be fouled.

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    patrick mannion from Greg Solow's Engine Room, January 15, 2012, 09:11
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     Master

    It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. Battery is OK if it cranks over sufficiently fast enough to support combustion.Check for fuel pressure (you will need a fuel pressure gauge and look up the specified fuel pressure for your vehicle). Remove the fuel hose that goes to the fuel rail and get a friend to crank over the engine to see you have adequate fuel volume (you should have approximately 1 pint of gasoline in ten seconds of cranking). Off course take proper precautions as gasoline is highly flamable. Next "listen" to the fuel injector. Using a mechanic's stethoscope (or use a long screw driver placing the handle end up to your ear place the metal tip end of the screwdriver against the body of the fuel injector), get a friend to crank over the engine while you "listen" to the fuel injector listen to each injector at the same point of the injector body. You should hear "click, click, click" as the injector is electrically opened and closed by the computer. If the injector is not being triggered you will not have fuel getting into the engine's cylinders. Disconnect the electrical connector at the fuel injector with the ignition key in the "on" position, (next position after the accessory position) you should have 12 volts at one of the two wires at the injector. This true for most vehicles but you need to consult a workshop manual for your vehicle to see that this is true for your vehicle. When the engine is running the second wire at the injector gets (triggered) grounded by the computer in your vehicle many times a second controlling exactly when and how much fuel gets injected into the engine. Check for ignition spark. Use caution when checking ignition spark firstly it provides very high voltage (about 15,000 to 40,000 volts) but it is low amperage, it can give an unexpected shock but is unlikely to kill anyone, secondly the spark produced can ignite any flammable gas or liquid (for example gasoline or the gaseous vapors of a lead acid battery). Remove the spark plug wire (or ignition coil if the ignition system on your car is coil over plug type), place an old spark plug with the gap between the electrode and shell of the spark plug "widened" to about .060" or .070" of an inch. Firmly ground the spark plug shell to a good engine ground. Hold the spark plug wire or coil with an insulated pliers and get a friend to crank over the engine while you watch for a pulsing bright spark jumping across the spark plug gap. Look on Youtube for a video on "Check for spark" or Check for ignition spark" I am sure someone has posted a good video clip. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online

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    djhyche, January 15, 2012, 09:44
     Rookie

    Thank you for your very informative help......I have checked the plug wire for fire by taking a screw driver and placing it in the end of the plug wire and grounding the shaft on the motor and could not see a spark not even a dull orange spark.....did this on the #2 and #4 cylinders.no fire on either...have not checked coil pacs which are located at the opposite end of the plug wire and plug into some kind of distributor housing...I am not familiar with....wondering if the crank sensor down by the harmonic balancer may also need replaced or checked..or is the a sensor or relay of some kind in the housing that the coil pacs plug into....dont know any thing really about non-distrubtor systems...

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    turtlerockett January 15, 2012, 13:11
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    My 99 4.3 died one day like that. Ended up being the rotor button. Replace it if you havnt done so recently.

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    djhyche, January 15, 2012, 14:10
     Rookie

    its a V6 vortex motor,fuel injected,there is no distributor or distributor cap.has coil packs for each cylinder.

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