I have 1975 Ford 4000 tractor. Haven't used it since November when I planted the fall plots. Went to crank it last week and all it would do is turn over, no firing. I drained the carb and put new fuel in, same results. I started with the carb, got a rebuild kit and rebuilt it. No change, same result. I learned something after I had rebuilt the carb that if you spray ether into the carb and it doesn't fire up for at least a few seconds, its not the carb
I moved on to the coil and the distributor. The distributor cap is new last year.
If I test the voltage on the + terminal and ground terminals on top of the coil I get about 8 volts.
If I leave the meter on the + terminal and use the - on the battery or the block, I get 12.75 volts.
So I'm thinking I have a bad coil and take if off.
If I put a volt meter on the + wire that I unhooked from the coil and the black wire I unhooked from the coil that runs to the distributor I get the 8 volts again. So no coil in between, just the + wire that I unhooked from the coil (it runs to the solenoid) and black wire I unhooked that runs to the distributor. about 8 volts.
Now if I leave the volt meter on the same + wire I unhooked from the coil and ground the volt meter to the - on the battery or the block, its the 12.75 volts.
Now I'm thinking maybe its not the coil maybe its getting a bad ground from the distributor or the distributor is bad.
So I tried to replicate a coil test I had read about. With the coil + wire back on the coil but wire that runs to the distributor off, I unhooked the center distributor wire that runs to the top of the coil from the distributor. I took a spark plug out and attached it to the end that normally goes to the center of the distributor. I attached a ground wire around the threads on the spark plug. According to the test, if I touch the end of the wire I attached to the base of the spark plug to the - on the battery, the spark plug should fire and throw a spark. Nothing ...zero spark. Back to thinking the coil isn't working unless I did the test wrong.
So I did something you're probably not supposed to do....trying something as a "what if" vs knowing if its the right thing or safe.
I know my + going to the coil is good, so I left it plugged in but ran a jumper from the - on the battery to the terminal on the coil that normally runs to the distributor. Now I KNOW I have a good + and - at the coil. So I try the spark plug test again with the spark plug hooked to the end of the center coil wire and a ground wire attached to the spark plug base.....drumb roll.......
Nothing, no spark.
So I put the volt meter back on the coil when KNOW its getting a good + and good - connection right to the battery. It still reads 8 volts from the coil terminal bolts, even though its direct wired to the battery. If I move the - volt meter wire to the - on the battery or the block, it goes back to 12.75 volts.
Apparently even with the coil direct to battery if you read from the coil terminals it will read 8 volts, but soon as you ground it to anything off the coil its 12.75 V
Now is when a mechanic/guru probably says, "No kidding, as the current goes through the coil and you read from the coil terminals, its going to be less" , not sure, thats my guess.
So I'm still a little stumped. I ordered a new coil anyway.
Here is the summary of what I know
1. Turns over fine, no fire at all with ether.
2. + coil wire will read 12.75 volts when grounded to anything but the terminal that has the wire that runs to the distributor. On the terminal ends of the coil, its 8 volts.
3. With the coil off and the volt meter on the + wire that runs to the solenoid and the wire (no longer attached to the coil) that runs to the distributor its 8 volts.
4. Coil terminals only read 8 volts even when wired directly to the battery.
5. If I hook up a spark plug to the end of the wire that comes from the center of the distributor and run a ground wire from the base of the plug and touch it to the - on the battery....no spark.
Any thoughts or suggestions ? Thanks
I moved on to the coil and the distributor. The distributor cap is new last year.
If I test the voltage on the + terminal and ground terminals on top of the coil I get about 8 volts.
If I leave the meter on the + terminal and use the - on the battery or the block, I get 12.75 volts.
So I'm thinking I have a bad coil and take if off.
If I put a volt meter on the + wire that I unhooked from the coil and the black wire I unhooked from the coil that runs to the distributor I get the 8 volts again. So no coil in between, just the + wire that I unhooked from the coil (it runs to the solenoid) and black wire I unhooked that runs to the distributor. about 8 volts.
Now if I leave the volt meter on the same + wire I unhooked from the coil and ground the volt meter to the - on the battery or the block, its the 12.75 volts.
Now I'm thinking maybe its not the coil maybe its getting a bad ground from the distributor or the distributor is bad.
So I tried to replicate a coil test I had read about. With the coil + wire back on the coil but wire that runs to the distributor off, I unhooked the center distributor wire that runs to the top of the coil from the distributor. I took a spark plug out and attached it to the end that normally goes to the center of the distributor. I attached a ground wire around the threads on the spark plug. According to the test, if I touch the end of the wire I attached to the base of the spark plug to the - on the battery, the spark plug should fire and throw a spark. Nothing ...zero spark. Back to thinking the coil isn't working unless I did the test wrong.
So I did something you're probably not supposed to do....trying something as a "what if" vs knowing if its the right thing or safe.
I know my + going to the coil is good, so I left it plugged in but ran a jumper from the - on the battery to the terminal on the coil that normally runs to the distributor. Now I KNOW I have a good + and - at the coil. So I try the spark plug test again with the spark plug hooked to the end of the center coil wire and a ground wire attached to the spark plug base.....drumb roll.......
Nothing, no spark.
So I put the volt meter back on the coil when KNOW its getting a good + and good - connection right to the battery. It still reads 8 volts from the coil terminal bolts, even though its direct wired to the battery. If I move the - volt meter wire to the - on the battery or the block, it goes back to 12.75 volts.
Apparently even with the coil direct to battery if you read from the coil terminals it will read 8 volts, but soon as you ground it to anything off the coil its 12.75 V
Now is when a mechanic/guru probably says, "No kidding, as the current goes through the coil and you read from the coil terminals, its going to be less" , not sure, thats my guess.
So I'm still a little stumped. I ordered a new coil anyway.
Here is the summary of what I know
1. Turns over fine, no fire at all with ether.
2. + coil wire will read 12.75 volts when grounded to anything but the terminal that has the wire that runs to the distributor. On the terminal ends of the coil, its 8 volts.
3. With the coil off and the volt meter on the + wire that runs to the solenoid and the wire (no longer attached to the coil) that runs to the distributor its 8 volts.
4. Coil terminals only read 8 volts even when wired directly to the battery.
5. If I hook up a spark plug to the end of the wire that comes from the center of the distributor and run a ground wire from the base of the plug and touch it to the - on the battery....no spark.
Any thoughts or suggestions ? Thanks
