motor turns over but won't start. on 1999 Jeep Wrangler

my 99 jeep wrangler started but then back fired, so my son turned it off now it turns over but won't start acts like its not getting enough fuel to start, can anyone give me any suggestions on what might be wrong?

by in Clinton, MI on October 02, 2010
1 answer 1 comment
ANSWER by on October 02, 2010
So many things can cause the engine not to start or stop running it is hard to guess at a cause without being able to do some diagnostic tests. An engine needs fuel, spark and mechanical integrity to run. Fuel pressure and volume is easy to check (even "opening" a fuel line while someone cranks the engine over will verify the presence of fuel but won't verify pressure). Ignition spark is easy to verify, and after that plugging in a scan tool to the 16 pin diagnostic socket under the dash can verify the operation of a lots of key engine sensors without having to do intrusive testing at each sensor. Many sensors on the engine are shared by both the ignition and fuel system, failure of any of these may cause an engine to stop running. Check for fuel pressure (you will need a fuel pressure gauge and look 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). 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 engines 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 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 spark at the spark plug to see if the ignition system is producing spark.
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COMMENT by on May 06, 2011
Do you here your fuel pump buzzing when you turn on your ignition switch? If not, try replacing the fuel pump relay. Joe
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