| Electronics > Projects, Designs, and Technical Stuff |
| Improvised oscilloscope probe for Automotive ignition analysis. |
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| Jim-0000:
--- Quote from: tautech on January 04, 2019, 07:09:32 am ---Things to double check: Battery to chassis and engine block grounds. Coil ground. Points plate ground. Broken cable conductors, typically old cabling where bending forces have broken the internal strands. Cracked dizzy cap or rotor. Dicky carbon and/or spring in the dizzy cap. --- End quote --- All good points and all will be checked again this Sunday. I hope to be assisting. I suspect point #1 the most. Battery is in the back, as I have explained. The distributor earthing is another one we will check, (I hope). |
| Jim-0000:
--- Quote from: joeqsmith on January 04, 2019, 04:57:59 am ---Maybe this will help: https://www.princeton.edu/ssp/tiger_cub/library/ignition_waveforms.pdf --- End quote --- I have already linked it in the first post. Very good paper from 1977. |
| Jim-0000:
--- Quote from: joeqsmith on January 04, 2019, 04:38:21 am ---Coax is RG400/U. I have a trimmer cap up near the clamp to trim the voltage level. The large braid goes to the block, the clamp goes around the plug wire. As mentioned, this forms a capacitive divider. I feed this into a 50 ohm termination (built into the scope). I test the ignition parts off the engine. --- End quote --- Where did you buy the clamp please Joe? |
| tautech:
--- Quote from: Jim-0000 on January 04, 2019, 08:18:25 am --- --- Quote from: tautech on January 04, 2019, 07:09:32 am ---Things to double check: Battery to chassis and engine block grounds. Coil ground. Points plate ground. Broken cable conductors, typically old cabling where bending forces have broken the internal strands. Cracked dizzy cap or rotor. Dicky carbon and/or spring in the dizzy cap. --- End quote --- All good points and all will be checked again this Sunday. I hope to be assisting. I suspect point #1 the most. Battery is in the back, as I have explained. The distributor earthing is another one we will check, (I hope). --- End quote --- Some points plates used a slipper contact while others used a very fine and soft braid or wire. If intact they give no problems but a slipper contact can if the wiper hasn’t enough tension. Good hunting. |
| soldar:
If the spark has enough voltage, and it should, and it only fails under load, that means is is not high enough to spark through the compressed mixture or it is sparking somewhere else. Some spark plugs can be defective and the spark jump internally. Or if the plug's cap are not good the spark can be jumping totally outside the plug directly to the block. Or it can be inside the coil. But you say all these items have been replaced.... Yeah, it's no fun troubleshooting something which happens only under heavy load. |
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