Testing coils on a coil over plug system?

[magnumv8]

Hey Art.....I personally have had cam and crank sensor failures that caused a loss of power and the engine did not want to run unless the rpms were up.....they can fail and send a false trigger signal to the ECU......


D L Rambo....

[art leong]

Originally Posted by magnumv8

Hey Art.....I personally have had cam and crank sensor failures that caused a loss of power and the engine did not want to run unless the rpms were up.....they can fail and send a false trigger signal to the ECU......


D L Rambo....

That sounds like my problem. I'll check them out in this order. Because the only way I know of the check the pickups is to replace them.
I'm going to wire a direct hot line to the ECU (bypassing switch panel). Then I'll check out the coils. If they are good I'm going to replace the ECU (They sent me a spare) If that isn't it I'll replace the pickups. Then If it isn't fixed I'll have thrown all the parts at it I can think of.
Today I started it up and was able to get it in gear with out to much trouble. I let it warm up fully then shut it down It got to late to start it up again (hot). I'll try it tomorrow If it gets worse when it's hot. I'm thinking coils.

[Ed Wright]

The correct way to diagnose those is checking the sensor wave forms with a good lab scope. Not by just throwing parts at it. You may find a poor ground or reference voltage issue instead of the sensor.

[buzzinhalfdozen]

Originally Posted by magnumv8

Hey Art.....I personally have had cam and crank sensor failures that caused a loss of power and the engine did not want to run unless the rpms were up.....they can fail and send a false trigger signal to the ECU......


D L Rambo....

Most modern Engine Management system only use the cam sensor @ start up to synchronize the fuel and Ign. events... most systems will continue to run correctly even if you unplug the cam sync. Now the crank sensor is a different story, yes they can be intermittent, and after reading back thru the posts I see Art's running a VR ( Variable Reluctance) sensor, this type of sensor is very sensitive to 2 things.... air gap and RFI. He could try making the gap slightly less or more and see if it effects the running. Most VR sensors run best @ .050 gap, check the resistance of the sensor, you can also hook up a DVOM set to AC volts with sensor unhooked crank engine sensor should produce about 1 volt AC while cranking.

[art leong]

Originally Posted by Ed Wright

The correct way to diagnose those is checking the sensor wave forms with a good lab scope. Not by just throwing parts at it. You may find a poor ground or reference voltage issue instead of the sensor.

Thanks Ed but I don't have a scope. And by the time I load up the car and take it to someone that does and knows how to use it. It would be much cheaper to just throw the parts at it.

Originally Posted by buzzinhalfdozen

Most modern Engine Management system only use the cam sensor @ start up to synchronize the fuel and Ign. events... most systems will continue to run correctly even if you unplug the cam sync. Now the crank sensor is a different story, yes they can be intermittent, and after reading back thru the posts I see Art's running a VR ( Variable Reluctance) sensor, this type of sensor is very sensitive to 2 things.... air gap and RFI. He could try making the gap slightly less or more and see if it effects the running. Most VR sensors run best @ .050 gap, check the resistance of the sensor, you can also hook up a DVOM set to AC volts with sensor unhooked crank engine sensor should produce about 1 volt AC while cranking.

I'll check the air gap on the crank sensor and try to check the sensor. Can I just hook up the wires to my volt meter (AC mode). And then crank the motor over with the starter?
I did move some wires around when I changed intakes and converters, I'll take a look to make sure nothing is running close and parallel.

[buzzinhalfdozen]

Art, yes hook up your meter and check the resistance, then switch meter to AC volts and crank the engine, you should see Approx. 1 volt AC give or take it depends on the cranking speed the faster it turns the higher the voltage. You said you moved some wires around... anything near the crank sensor or it's wiring? As I said these type sensors are quite sensitive to interference. By the way is this sensor shielded? Also as Ed stated there's no real replacement for proper diagnsis, I realize not everyone has a scope on hand... however by simply replacing a part you could be missing many things, poor connections broken wires ect. that's why that strategy sometimes back fires on people. We see alot of vehicles from other shops that have had large amounts of parts hung only to find simple wiring issues as the source of the problem. We have alot of customers balk at our charge to diag. their veh. however with a proper diagnosis a sucessful repair is almost guaranteed.

[art leong]

Originally Posted by buzzinhalfdozen

Art, yes hook up your meter and check the resistance, then switch meter to AC volts and crank the engine, you should see Approx. 1 volt AC give or take it depends on the cranking speed the faster it turns the higher the voltage. You said you moved some wires around... anything near the crank sensor or it's wiring? As I said these type sensors are quite sensitive to interference. By the way is this sensor shielded?

Nothing in the front of the motor was touched. But the cam sensor (hall effect) wires were moved a bit whe I put new trans in, then moved again when I changed intakes.
I called msd a while back, and asked how to check the cam sensor. They said if the light is on it's fine, that there is no other way to check it other than replace it.

[buzzinhalfdozen]

So you're running an MSD Ign. and a seperate controller for fuel? And yes they are partially right... if it has a cam sync LED that blinks it is seeing the signal however a hall sensor is easily checked, you could even use a DVOM if it has a fast enough sample rate, most switch from 0 to 5 volts. Adger had stated that you are seeing the engine go lean during the event is this the case and if so what reading are you getting?

[art leong]

Originally Posted by buzzinhalfdozen

So you're running an MSD Ign. and a seperate controller for fuel? And yes they are partially right... if it has a cam sync LED that blinks it is seeing the signal however a hall sensor is easily checked, you could even use a DVOM if it has a fast enough sample rate, most switch from 0 to 5 volts. Adger had stated that you are seeing the engine go lean during the event is this the case and if so what reading are you getting?

No mds ignition, only a hall effect sensor on my intake cam. The wires from it are in the back of the motor (drivers side in my case). And my battery and wires are also in close proximity. When changing the trans all these wires were moved a bit to get at the bolts etc. Again as always I got "excellent" customer service from msd. They said there was no way to check the sensor. I would have checked it way back on my list if I knew it could be done.
I was going lean during the 2 step operation. Which I believe is normal. During the stalls it doesn't seems to indicate anything but slowing to a stop.

[buzzinhalfdozen]

Art, as I stated before, and this is just my opinion from nearly 30 years of driveabilty diagnosis. A crank or cam sensor issue will 99% of the time result in an immediate stall, not slowly quit running. Basically if this engine runs normally in nuetral and you place it in gear you are really only doing 1 thing, increasing the load. The sensor responsible for measuring engine load is the MAP sensor. You said it seems to read normally, what BAR sensor are you using, after quickly scanning some of your systems operating capabilities I saw that you can use MAP or Throttle pos. as your load measurement. From my perspective the engine needs 2 things to happen when it's loaded 1 the fuel needs to increase and 2 the spark instant needs to increase. From what you're saying the engine just seems to slow down to the point of quitting which to me at least indicates it is lacking in proper amount of fuel or spark lead to maintain it's desired idle speed. If I understand correctly you have an indicator lite for Cam sync input? Perhaps on the ECU, if so does this lite quit blinking just prior to stall. Sorry for all the questions but I'm really baffled by this situation and trying to determine what's Not causing it.