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Steps needed to diagnose injectors :
Safety first . Be careful around engine compartment . Avoid moving parts and electrical parts that might shock you . Wear safety glasses and gloves .
Read all steps first . If your primary concern is injectors , then this diagnose will help . It is not necessary for there to be fuel pressure in the fuel lines since it is not the fuel pump or pressure that determines when the injectors open .
1 - Multimeter - Turn car off . Disconnect injector electrical connector and measure the resistance of the injector by placing multimeter to read ohms . Resistance varies by make and model . Average is 15 ohms for some GM models . Refer to a Haynes or Chilton manual for specific resistance value . If it passes resistance test that means that the electrical portion of the injector is ok .
2 - Noid light (available for rental at some auto parts stores including Advance Auto Parts ) - Disable coil(s) so car won't start by accident . Disconnect electrical connector to injector . Connect noid light to electrical connector . Crank ( not start ) engine using key switch (not a remote starter ) and look to see that the noid light flashes/lights up steadly . If it lights up then the connector is carrying voltage to injector . If it didn't light up the wires might have a short or computer is defective . Check the all fuses , relays , and engine codes ( if any ) before determining a short or computer is At Fault .
3 - Stethoscope/screwdriver - Leave the coil(s) diabled . If the injector is at least getting voltage ( step 2 ) then you can perform the third and most important test . Recconect the electrical connector to the injector . Have a friend Crank ( not start ) the engine using key switch ( not remote starter ) while you place the stethoscope against injector and listen for a clicking sound . This is the sound of injector opening . If you do not have a stethoscope , $14 at Sears , then place a long screwdriver against injector and listen through handle (avoid coming in contract with engine , specially electrical and moving parts ) . If you don't hear any sound coming from injector then it is failing to open and this means the injector is BAD .
- Step 3 can be performed with one person with the engine running , vehicle in Park Position , and wheels shocked . Remember to stay away from moving parts and anything electrical that might shock you .
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