'94 Jetta III Gl 2.0 5 spd problem

[large_arge]

Every once in a while my car will not start. It will crank fine but no spark. 8 months ago I changed the coil, and the entire distributor. 2 weeks ago after work it would not start and I had to have it towed home. I was not getting any secondary spark from the coil. I tested coil and it tested as bad so I replaced. Still no spark. Bought a used ECM and still nothing. I am only getting 5 volts at the 2 outside prongs of the Hall sender. Tried everything I could think of and still nothing. Today I unplugged the Knock sensor and the dang thing started. I plugged back in and it is now running. I am at a loss. Would a bad knock sensor cause a no spark occurrence? I believe the crank position sensor plug is located next to the knock sensor plug and I moved the wires around some but did not unplug. Could it be short in either one fo these plugs? I do not trust the vehicle at this time and am at my wits end. Also, I still only have 5 volts at the Hall sender but it is running. ANy suggestions?

Thanks

[stuzman]

Originally Posted by large_arge

Every once in a while my car will not start. It will crank fine but no spark. 8 months ago I changed the coil, and the entire distributor. 2 weeks ago after work it would not start and I had to have it towed home. I was not getting any secondary spark from the coil. I tested coil and it tested as bad so I replaced. Still no spark. Bought a used ECM and still nothing. I am only getting 5 volts at the 2 outside prongs of the Hall sender. Tried everything I could think of and still nothing. Today I unplugged the Knock sensor and the dang thing started. I plugged back in and it is now running. I am at a loss. Would a bad knock sensor cause a no spark occurrence? I believe the crank position sensor plug is located next to the knock sensor plug and I moved the wires around some but did not unplug. Could it be short in either one fo these plugs? I do not trust the vehicle at this time and am at my wits end. Also, I still only have 5 volts at the Hall sender but it is running. ANy suggestions?

Thanks

I looked at the wiring for the camshaft sensor for a 94 and it shows that pins 2 and 3 are going back to the ECM and pin 1 is going to ground. So, the voltage between pins 1 and 3 that you measured are probably okay (it sounds like it's TTL). Even in the service manual, it says that there should be a minimum of 4VDC. Just out of curiosity, I looked up the diagram for a 96 (which is what I have) and pin three goes back to 12V through the ignition. So, in your case, I'm sure the 5VDC is correct. You can hook up a scope or DMM to pins 2 and 1 and see if you get a signal from the sensor when the engine is cranking.

How did you check the coil? As far as the knock sensor, it wouldn't be the first item on my list, but a wire from it being grounded out could probably create a no-start. Do you have a diagram for this car?

[large_arge]

Originally Posted by stuzman

I looked at the wiring for the camshaft sensor for a 94 and it shows that pins 2 and 3 are going back to the ECM and pin 1 is going to ground. So, the voltage between pins 1 and 3 that you measured are probably okay (it sounds like it's TTL). Even in the service manual, it says that there should be a minimum of 4VDC. Just out of curiosity, I looked up the diagram for a 96 (which is what I have) and pin three goes back to 12V through the ignition. So, in your case, I'm sure the 5VDC is correct. You can hook up a scope or DMM to pins 2 and 1 and see if you get a signal from the sensor when the engine is cranking.

How did you check the coil? As far as the knock sensor, it wouldn't be the first item on my list, but a wire from it being grounded out could probably create a no-start. Do you have a diagram for this car?

Thanks for the reply and the information. The only wiring diagram I have are what was in the Chilton's manual and the manual I checked out at the Library. I tested the coil with an Ohm meter and the secondary circuit showed to be completely open. I drove the car to work today and it is running fine. I will continue trouble shooting and update as well.

Thanks again.