Re: i istalled the wrong installed the wrong spark plugs!!!!!
To check if the coil mounting plate is properly grounded to the block, set you meter to OHMs. If it's not an auto-ranging meter, set it to the lowest setting for OHMs. Put one lead on the block, the other on the mounting plate. Make sure you're getting a good connection. Sometimes the paint and crud will need to be cleaned off. You should read a dead short. There should be a black wire that is attached to the mounting plate and the block. You'll have to kind of look around for it. This wire is what connects the two together (plate to the block).
The coil ground wires are on the back side of the mounting plate. The wire is attached to one of the bolts that mounts the coil to the plate. Just make sure they are there and connected. Taking the plate off the motor to check them is probably not worth the effort and can create problems if you aren't careful.
Next I would do the idle test and momentarily pull a plug wire off to see if the idle changes. If it does not, note the cylinder. It may be helpful in focusing on where to look next. If I were a betting man, I would bet that when you pull #4 off, the idle won't change. I could be wrong though. You never know, and don't assume anything.
Next check the rectifier. Easiest way to check this is to disconnect the two Green/Yellow wires going to it. Tape the ends off and perform the idle test again. If the problem goes away, replace it. Radio Shack has a replacement full wave bridge rectifier for less than $5.
Next check the resistance of the stator. Follow the two Blue wires and two Yellow wires that come out from underneath the flywheel. These are the stator windings that supply the voltage to the two CD modules. They go to the 12 position terminal block on the side of the block. The wires should have numbers on them 1 - 4. Don't get them confused with the Blue and Yellow wires that come from the CD modules. They are also marked 1 - 4. Note which terminals they are attached to. Disconnect the Blue and Yellow stator wires marked 1 & 2. Measure the resistance resistance between them. It should read between 680 and 850 OHMs. Reconnect them and do the same thing with the Blue and Yellow stator wires marked 3 and 4. Note, the reading on each par should be within 5 or 10 OHMs of each other. Also, make sure your fingers are not touching the metal part of the leads or stator wires. The meter might read your body resistance and not give a true stator winding resistance reading.
If everything checks out OK, then you may have a bad/weak CD module or coil. First switch #4 coil , or which ever cylinder didn't change in idle speed with one of the other ones and perform the idle test momentarily pulling off a plug wire. If the problem doesn't move then you know it's not a coil. Next reverse the two CD modules. This is where things can easily go wrong if you aren't careful. Make sure you have a good understanding of what you're going to do with the wires and what terminals they are going to go on. Do the idle test again and if the problem moves, then you probably have a bad/weak CD module.
Looking at the spark with a tester or a grounded plug outside the motor gives you a general idea of the spark energy and you can sometimes see a difference, blue or bluish almost clear color spark is good, orange no so good but this test is pretty subjective. Different people see different things especially if they are borderline. What the spark test doesn't do is give you an indication of how the spark is performing inside the cylinder during actual running conditions. Running conditions inside a cylinder are completely different than outside of the cylinder.
To check if the coil mounting plate is properly grounded to the block, set you meter to OHMs. If it's not an auto-ranging meter, set it to the lowest setting for OHMs. Put one lead on the block, the other on the mounting plate. Make sure you're getting a good connection. Sometimes the paint and crud will need to be cleaned off. You should read a dead short. There should be a black wire that is attached to the mounting plate and the block. You'll have to kind of look around for it. This wire is what connects the two together (plate to the block).
The coil ground wires are on the back side of the mounting plate. The wire is attached to one of the bolts that mounts the coil to the plate. Just make sure they are there and connected. Taking the plate off the motor to check them is probably not worth the effort and can create problems if you aren't careful.
Next I would do the idle test and momentarily pull a plug wire off to see if the idle changes. If it does not, note the cylinder. It may be helpful in focusing on where to look next. If I were a betting man, I would bet that when you pull #4 off, the idle won't change. I could be wrong though. You never know, and don't assume anything.
Next check the rectifier. Easiest way to check this is to disconnect the two Green/Yellow wires going to it. Tape the ends off and perform the idle test again. If the problem goes away, replace it. Radio Shack has a replacement full wave bridge rectifier for less than $5.
Next check the resistance of the stator. Follow the two Blue wires and two Yellow wires that come out from underneath the flywheel. These are the stator windings that supply the voltage to the two CD modules. They go to the 12 position terminal block on the side of the block. The wires should have numbers on them 1 - 4. Don't get them confused with the Blue and Yellow wires that come from the CD modules. They are also marked 1 - 4. Note which terminals they are attached to. Disconnect the Blue and Yellow stator wires marked 1 & 2. Measure the resistance resistance between them. It should read between 680 and 850 OHMs. Reconnect them and do the same thing with the Blue and Yellow stator wires marked 3 and 4. Note, the reading on each par should be within 5 or 10 OHMs of each other. Also, make sure your fingers are not touching the metal part of the leads or stator wires. The meter might read your body resistance and not give a true stator winding resistance reading.
If everything checks out OK, then you may have a bad/weak CD module or coil. First switch #4 coil , or which ever cylinder didn't change in idle speed with one of the other ones and perform the idle test momentarily pulling off a plug wire. If the problem doesn't move then you know it's not a coil. Next reverse the two CD modules. This is where things can easily go wrong if you aren't careful. Make sure you have a good understanding of what you're going to do with the wires and what terminals they are going to go on. Do the idle test again and if the problem moves, then you probably have a bad/weak CD module.
Looking at the spark with a tester or a grounded plug outside the motor gives you a general idea of the spark energy and you can sometimes see a difference, blue or bluish almost clear color spark is good, orange no so good but this test is pretty subjective. Different people see different things especially if they are borderline. What the spark test doesn't do is give you an indication of how the spark is performing inside the cylinder during actual running conditions. Running conditions inside a cylinder are completely different than outside of the cylinder.
