951S With No Spark
04-13-2005, 03:33 PM
#16
Race Director
Dimitry, I like to work backwards from the end results first because it tells you a lot about ALL of the components in between without having to troubleshoot each and every single one.
I. So the very first test I do is check the speed/ref. signal at the DME connector (which also happens to be the very first step in the DME/KLR Service Manual). It will check your sensor's output as well as alignment, and the wiring-harness in between in one easy step. Then work backwards. If no signal at the DME connector, but at the sensor-plugs, then harness is bad. If signal at sensor plug is weak, then sensor's alignment is bad. If no signal at sensor plugs at all, sensor is probably bad.
A 'scope is the only tool you can use to check the speed/ref. sensors really. But it sounds like your sensors are OK if you're getting spark. The waveforms should look like this:
This tells you instantly whether you're getting the proper signal. I've seen people troubleshoot by swapping plugs, swapping plug-wires, distributor and rotor, coil, injectors, injector-harness, fuel-pressure, FPR & dampener, fuel-pump, fuel-pump wiring, DME-relay, etc, etc., etc. when all they had to do was check the sensor signal to see that they've got a bad sensor.
II.Same thing with the spark, pull the spark-wire and spark-plug. Stick spark-plug back into connector and lay on the intake-manifold to ground and crank to see if you've got spark. This will test the plugs, the plug-wires the distributor, the rotor, the coil all in one step. Then work backwards. If no spark, replace plug with, known good one. If not, then pull center wire from distributor and stick a plug into it to test the coil. If spark here, but not at end of plug-wires, then either the wires, the distributor or rotor is bad (or mis-aligned).
"I also took a test light, and the negative side of the coil was not flashing (Indicating no signal from DME). The DME does have power from the DME relay. I'll check wiring and connection tonight."
How did you hook up the test-light? Both sides of the coil is hot and the DME grounds the green wire going to the coil to collapse the field. The way you would hook up the test-light is ground one end to the body, like the bolt that clamps down the coil. Touch the +positive lead to the green wire on the coil. The light should always be on, then when the coil fires, the light blinks off. It's a very short-duration signal, less than 10ms and the bulb may not dim long enough for you to catch it.
"I'm checking spark out of the coil - not from the plug wires."
So you get a spark if you stick a plug into the center-wire that goes to the distributor? Just no spark coming out of the individual plug wires? That sounds like a problem with the distributor rotor, cap or plug-wires. I think you did the simplest and easiest test and it shows you've got spark coming from the coil. So the DME must be working correctly.
III. Same methodology with the fuel. Yank the fuel-rail and put little clear plastic cups under each injector to catch the fuel. Crank the engine over and see if you've got fuel-squirting out. This tests the injectors, the injector wiring, the fuel-rail, the FPR, the fuel-pump, the fuel-filter all in one step. If you've got fuel squirting into the cups, all those components are fine. If not, work backwards, measure the impedance of each injector, measure the differences in fuel-volumes collected in the cups.
Then measure the connectors for shorts (with DME/ISV/CV disconnected, key ON, should have power to ALL the rearward pins on each connector, no power to front pin). Then measure continuity between the forward pins and the DME connector to verify wiring in between.
I. So the very first test I do is check the speed/ref. signal at the DME connector (which also happens to be the very first step in the DME/KLR Service Manual). It will check your sensor's output as well as alignment, and the wiring-harness in between in one easy step. Then work backwards. If no signal at the DME connector, but at the sensor-plugs, then harness is bad. If signal at sensor plug is weak, then sensor's alignment is bad. If no signal at sensor plugs at all, sensor is probably bad.
A 'scope is the only tool you can use to check the speed/ref. sensors really. But it sounds like your sensors are OK if you're getting spark. The waveforms should look like this:
This tells you instantly whether you're getting the proper signal. I've seen people troubleshoot by swapping plugs, swapping plug-wires, distributor and rotor, coil, injectors, injector-harness, fuel-pressure, FPR & dampener, fuel-pump, fuel-pump wiring, DME-relay, etc, etc., etc. when all they had to do was check the sensor signal to see that they've got a bad sensor.
II.Same thing with the spark, pull the spark-wire and spark-plug. Stick spark-plug back into connector and lay on the intake-manifold to ground and crank to see if you've got spark. This will test the plugs, the plug-wires the distributor, the rotor, the coil all in one step. Then work backwards. If no spark, replace plug with, known good one. If not, then pull center wire from distributor and stick a plug into it to test the coil. If spark here, but not at end of plug-wires, then either the wires, the distributor or rotor is bad (or mis-aligned).
"I also took a test light, and the negative side of the coil was not flashing (Indicating no signal from DME). The DME does have power from the DME relay. I'll check wiring and connection tonight."
How did you hook up the test-light? Both sides of the coil is hot and the DME grounds the green wire going to the coil to collapse the field. The way you would hook up the test-light is ground one end to the body, like the bolt that clamps down the coil. Touch the +positive lead to the green wire on the coil. The light should always be on, then when the coil fires, the light blinks off. It's a very short-duration signal, less than 10ms and the bulb may not dim long enough for you to catch it.
"I'm checking spark out of the coil - not from the plug wires."
So you get a spark if you stick a plug into the center-wire that goes to the distributor? Just no spark coming out of the individual plug wires? That sounds like a problem with the distributor rotor, cap or plug-wires. I think you did the simplest and easiest test and it shows you've got spark coming from the coil. So the DME must be working correctly.
III. Same methodology with the fuel. Yank the fuel-rail and put little clear plastic cups under each injector to catch the fuel. Crank the engine over and see if you've got fuel-squirting out. This tests the injectors, the injector wiring, the fuel-rail, the FPR, the fuel-pump, the fuel-filter all in one step. If you've got fuel squirting into the cups, all those components are fine. If not, work backwards, measure the impedance of each injector, measure the differences in fuel-volumes collected in the cups.
Then measure the connectors for shorts (with DME/ISV/CV disconnected, key ON, should have power to ALL the rearward pins on each connector, no power to front pin). Then measure continuity between the forward pins and the DME connector to verify wiring in between.
Last edited by Danno; 04-13-2005 at 03:53 PM.
04-13-2005, 09:25 PM
#17
Rennlist Member
Thread Starter
Danno - There is no spark coming out of the coil at all. The field is not being collapsed. Bummer, now I have to go see if my boss will let me borrow his Vantage so i can graph the signals.
04-13-2005, 10:04 PM
#18
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why got to all that trouble? just borrow the sensors from Tom and slap em in there. Shouldn't take ya more than a few minutes.
Did the sensors pass the clarks-garage test?
Did the sensors pass the clarks-garage test?
04-14-2005, 03:38 PM
#19
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Dmitry,
My Jedi Master Auto Technology teacher would allways reinterate.....KISS!
Which in auto mechanic speak means, Keep It Simple Stupid.
Like Danno says, start at the plugs. If the plugs are sparking, you have eliminated the entire electrical system, so look to another system. If no spark, work backwards from the end.
Not the middle.
More often than not, you will find the problem closer to the end than the start of a system. If you start at the middle, you will not know which way to go.
My Jedi Master Auto Technology teacher would allways reinterate.....KISS!
Which in auto mechanic speak means, Keep It Simple Stupid.
Like Danno says, start at the plugs. If the plugs are sparking, you have eliminated the entire electrical system, so look to another system. If no spark, work backwards from the end.
Not the middle.
More often than not, you will find the problem closer to the end than the start of a system. If you start at the middle, you will not know which way to go.