Bruce
08-01-2004, 08:26 AM
The basic tools you need are:
An Injector Noid Light
An Air gap tool, for testing for spark, it must demand that the spark jump at leas 1/2" air gap.
An LED trouble light
Advanced tools:
Direct Scan
Cam sensor adjuster
Ohm Meter
What an engine needs to run:
Fuel in the correct amount
Spark at the right time
Compression
Usually the lack of compression, is an easy one. The motor just spins without any drag on the starter. The test is using a compression guage and making sure you do have at least some compression. Reads of less then 80 PSI, and you have serious problems.
Spark.
You want to test at the spark plug end of the plug wire, and make sure you have a large bright spark, at least 1/2" long. You also have to make sure there is a place in the cylinder for the spark to happen. 6 wet/heavily fouled plugs will stop an engine from starting just as effectively as a dead module. If you don't have spark then you need to back track from there. Check the fuse box, and make sure ALL the fuels are OK. Then pull the connector off the ignition module and make sure you have power at the pink/black wires. Obviously when I say check for power make sure the key is on. If you have power, then hook up you Direct Scan and crank the engine, do you see an rpm displayed when cranking?. If you do, then you know the crank sensor is OK. If you see an rpm displayed, then you want to next check for the cam sensor working. If you have cam and crank sensors functioning, then you have a dead module or coils. It'd be rare to have all three coils die, but check them with an ohm meter if possible.
If you had spark, and compression, then the only other thing is fuel.
Put the injector Noid light in, and crank the engine. Does the light flicker?. If not check for 12v at the injector connector. If you have 12v then the problem is the ecm isn't grounding the injector to fire it. It would be an open wire, or dead ecm. It's rare to see all 6 injector drivers die at the same time, or all 6 wires go open (unless you forgot to plug the injecot harness in). Oh, a *no ground* condition for the ecm would do it, so check the grounds on the back of the head.
If the injectors are firing, and you have spark, and compression, then the next item is to make sure you have fuel, and that it has enough pressure. Hook up the fuel pressure guage, and that'll tell you if it's right. If not then make sure the pump is fine electrically. You should hear it run when you first turn on the key, for a second or two.
Diagnostics just mean using some logic, and looking at the situation. Stay calm, if you're frustrated, you can make mistakes, or overlook the obvious.
And at times, you can have several items fail at once so again don't lose your calm.
*******
An LED trouble light.
I haven't seen one commercially available, but what I ALWAYS carry is a lil dodad, that I made from a Radio Shack Bright LED, a couple jumper wires, and a 1K ohm resistor. I took and soldered the resistor to one leg of the LED, and then a jumpre wire to that, and then one to the other leg. Then used heat shrink on all of it. And always remember LEDs are polarity sensitive. So if you're looking for a problem, be sure you have it hooked up correctly. There are bipolarity LEDs, but, IMO they just ain't bright enough for using on the side of the road in sunlight. If you make one, might play with it some to make sure it's working, and you know how to make sure you have a cam sensor pulse, etc.. Nothing worse then having the tools and not know how to use them when you need them. There are also any number of universal Weatherpack connector interceptor harnesses for diagnostics. Generally they have 4 wires and some easy to tap into thingies, so that you and say unplug the cam sensor, plug in that harness thingie, then hook up your LED and make sure the sensor is in fact triggering.
I'm not trying to give you a total *look here* do it this way blow by blow list off all the ways things can fail, but rather introduce you to the thought pattern of diagnostics, and a how to be able to track something down.
HTH
An Injector Noid Light
An Air gap tool, for testing for spark, it must demand that the spark jump at leas 1/2" air gap.
An LED trouble light
Advanced tools:
Direct Scan
Cam sensor adjuster
Ohm Meter
What an engine needs to run:
Fuel in the correct amount
Spark at the right time
Compression
Usually the lack of compression, is an easy one. The motor just spins without any drag on the starter. The test is using a compression guage and making sure you do have at least some compression. Reads of less then 80 PSI, and you have serious problems.
Spark.
You want to test at the spark plug end of the plug wire, and make sure you have a large bright spark, at least 1/2" long. You also have to make sure there is a place in the cylinder for the spark to happen. 6 wet/heavily fouled plugs will stop an engine from starting just as effectively as a dead module. If you don't have spark then you need to back track from there. Check the fuse box, and make sure ALL the fuels are OK. Then pull the connector off the ignition module and make sure you have power at the pink/black wires. Obviously when I say check for power make sure the key is on. If you have power, then hook up you Direct Scan and crank the engine, do you see an rpm displayed when cranking?. If you do, then you know the crank sensor is OK. If you see an rpm displayed, then you want to next check for the cam sensor working. If you have cam and crank sensors functioning, then you have a dead module or coils. It'd be rare to have all three coils die, but check them with an ohm meter if possible.
If you had spark, and compression, then the only other thing is fuel.
Put the injector Noid light in, and crank the engine. Does the light flicker?. If not check for 12v at the injector connector. If you have 12v then the problem is the ecm isn't grounding the injector to fire it. It would be an open wire, or dead ecm. It's rare to see all 6 injector drivers die at the same time, or all 6 wires go open (unless you forgot to plug the injecot harness in). Oh, a *no ground* condition for the ecm would do it, so check the grounds on the back of the head.
If the injectors are firing, and you have spark, and compression, then the next item is to make sure you have fuel, and that it has enough pressure. Hook up the fuel pressure guage, and that'll tell you if it's right. If not then make sure the pump is fine electrically. You should hear it run when you first turn on the key, for a second or two.
Diagnostics just mean using some logic, and looking at the situation. Stay calm, if you're frustrated, you can make mistakes, or overlook the obvious.
And at times, you can have several items fail at once so again don't lose your calm.
*******
An LED trouble light.
I haven't seen one commercially available, but what I ALWAYS carry is a lil dodad, that I made from a Radio Shack Bright LED, a couple jumper wires, and a 1K ohm resistor. I took and soldered the resistor to one leg of the LED, and then a jumpre wire to that, and then one to the other leg. Then used heat shrink on all of it. And always remember LEDs are polarity sensitive. So if you're looking for a problem, be sure you have it hooked up correctly. There are bipolarity LEDs, but, IMO they just ain't bright enough for using on the side of the road in sunlight. If you make one, might play with it some to make sure it's working, and you know how to make sure you have a cam sensor pulse, etc.. Nothing worse then having the tools and not know how to use them when you need them. There are also any number of universal Weatherpack connector interceptor harnesses for diagnostics. Generally they have 4 wires and some easy to tap into thingies, so that you and say unplug the cam sensor, plug in that harness thingie, then hook up your LED and make sure the sensor is in fact triggering.
I'm not trying to give you a total *look here* do it this way blow by blow list off all the ways things can fail, but rather introduce you to the thought pattern of diagnostics, and a how to be able to track something down.
HTH