Random's Non-Start Troubleshooting Advice
10-14-2014, 12:47 PM
#1
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Random's Non-Start Troubleshooting Advice
This was good enough to justify a sticky.
Start with the basics...after cranking pull a spark plug. Is it wet? If not, you're not getting fuel. Check the fuel system (pump, fuze, lines, filter)
If it's wet, then you've got fuel, but no spark
That spark plug you just pulled, leave it attached to the plug wire and ground plug against HEAD/Intake Manifold or Engine Block (WEAR RUBBER GLOVES). Have someone crank the engine. Do you see a spark firing? If not, there's your problem. Check your coil packs, plugs, plug wires, Crank Position Sensor and Cam Position Sensor.
If you've got Fuel and Spark...your problem is air...or ECU.
Easy enough to test for air. Leave throttle 1/4 cracked and crank engine. If it won't start, and the plugs are wet (but have spark) when you pull them...then things MIGHT get ugly.
If Fuel, Spark and AIR are all good...then you've got a wacked out sensor somewhere. Check them all. TPS? Cam Position Sensor, Crank Position Sensor, Knock Sensor, MAF/MAP and TPS Chances are one if them is reading screwy. If you've got access to an OBD-2 reader, it will make life much easier. You should be able to get a static listing of all sensors values with the ignition on...then check the values with the engine turning. If anything goes wacky once the engine is rotating...you either mixed up sensors/plugs or youve got a bad sensor.
Check for wet/gassy spark plugs first. If they are dry, I's probably either a fuel pump circuit(blown fuse) or clogged fuel rail or something similar. Did you reuse YOUR fuel rail and YOUR injectors? If not, consider it. Who knows what condition those injectors were/are in, ditto for that fuel rail.
If it's wet, then you've got fuel, but no spark
That spark plug you just pulled, leave it attached to the plug wire and ground plug against HEAD/Intake Manifold or Engine Block (WEAR RUBBER GLOVES). Have someone crank the engine. Do you see a spark firing? If not, there's your problem. Check your coil packs, plugs, plug wires, Crank Position Sensor and Cam Position Sensor.
If you've got Fuel and Spark...your problem is air...or ECU.
Easy enough to test for air. Leave throttle 1/4 cracked and crank engine. If it won't start, and the plugs are wet (but have spark) when you pull them...then things MIGHT get ugly.
If Fuel, Spark and AIR are all good...then you've got a wacked out sensor somewhere. Check them all. TPS? Cam Position Sensor, Crank Position Sensor, Knock Sensor, MAF/MAP and TPS Chances are one if them is reading screwy. If you've got access to an OBD-2 reader, it will make life much easier. You should be able to get a static listing of all sensors values with the ignition on...then check the values with the engine turning. If anything goes wacky once the engine is rotating...you either mixed up sensors/plugs or youve got a bad sensor.
Check for wet/gassy spark plugs first. If they are dry, I's probably either a fuel pump circuit(blown fuse) or clogged fuel rail or something similar. Did you reuse YOUR fuel rail and YOUR injectors? If not, consider it. Who knows what condition those injectors were/are in, ditto for that fuel rail.
10-14-2014, 07:43 PM
#2
Super Moderator
I would argue the FIRST thing, before pulling out any tools, is to grab a scantool with monitoring. Check for codes and associated freeze frame data.