Back from a recent trip to mexico and am tired of fighting my bad ground any longer. I have a 70' FJ40, original F with a 78' distributor and a Jacobs electronics electronic ignition set-up. A few months back I posted that I was having trouble starting the truck, it would turn over fine until the Jacobs would fire, then it would die, then slowly start turning over again. The only way it would start would be if by chance the motor was in the right posotion so that the key could be turned back to run, giving the power to the Jacobs, and have enough momentum to fire. Once started, the amp arm would peg and remain between full and half way up as long as it ran. So a ground problem was suspected. I have searched for months for this damn bad ground and have yet to uncover it. I've tried unplugging everything I can, but it still does it. I'm wondering if it could be the Jacobs Box, and if so, how do I test it? Is there a way I can bypass all the electrical and only run the truck with the battery, alt and ignittion hooked up? How do I wire it to do that? Any thoughts would be greatly appreciated.

ON a lighter note, besides the starting/electrical issue the truck did great over the 8000 mile treck to jungles of the Yucatan. Not a single broken part, well except those two winch cables and a tow rope. And the motor, (F, rebuilt head, Jacobs ignition, tri y headers, weber 38) ran great and besides the actual miles (now over 185,000) the hours were tremendous due to the fact that it ran basically from sun up to sun down (didn't want to face the will it start battle but once a day).

Gotta love these little things!

tom

I wouldn't assume it is a ground problem from just what you described. It sounds like a couple of things simultaneously:
1) The ignition wire from the starter motor to the ignitor/coil is missing or has a bad connection. This wire bypasses the ballast resistor so that the ignitor gets more voltage when cranking as there is a substantial voltage drop when the starter motor is working.
2) The fact that the engine cranking slows when the coil trys to fire suggests that the ingition timing is too advanced, at least at the static setting.

If there is a gorounding problem associated with this it may be the ground strap from the engine to the frame is missing.

Thanks for the responce pin head.

I have replaced the ground strap from the motor to frame, the ground wire for the battery, the starter, the coil wire 3 times (they are replaced free of charge by Jacobs) and yet the problem persists.

I am not sure of the bypass wire you refer to. When I replaced the starter I hooked everything up as before. Would the wiring need to be changed since this was a 70' points type dist swapped out with a 78' magnetic pick-up style dist? On the original starter there were 2 wires, one wire from the battery and one from the ignition switch, however the new starter I have has an extra black wire that comes off the starter. I was told just to tape it off and leave it. Is this right?

What about the amp meter always reading a full or almost full charging situation? I have a new battery and voltage regulator.

This is a bear of a problem. Everything ran great when the Jacobs was first installed, but after about 6 months, this problem began. This is why I would like to bypass everything and run the truck on just the minimum to find out if it is in the heart or out in the body.

thanks
tom

There is supposed to be a large gauge (10-12 ga) wire (black with yellow stripe) going from the spade lug on the passenger side of the starter solenoid to the + side of the ignition coil. This bypasses the key ignition circiut that goes through the ballast resister so that it can deliver a higher voltage to the coil during cranking. Check your spark during cranking and if it isn't hot and consistent (It should jump a 1/4 inch gap with a crack), then you need this wire for reliable starts. You need a Toyota wiring schematic too.

The pegged ammeter thing is normal after cranking but it should drop down to the middle after 10-20 min. If it is still pegged, double check the current from the alternator to see if the gauge is lying. Otherwise, maybe your new voltage regulator isn't doing its job.

thanks, i'll look into the wire this weekend and double check the voltage regulator.
tom

When I had the straight six in my L/C.
I did the same thing with a late model dist in a 72, I was having the same problem. It would'nt idle on its own. Until I connected that dam black wire, off the starter that every one was saying dosnt need to be connected. It ran fine after connecting it the right way.

So here is what I have. There is a solid black wire coming off the solenoid on the driver side and a black and white wire comming off the passenger side of the solenoid. The black and white wire goes to the ignition switch and the black wire is just left hanging there.

I'm running a jacobs ignition with a 78' distributor. Where do these wires need to go? If anyone out there has a jacobs and a later model dist, how did you hook everything up?

thanks
tom

The large black wire that is dangling should go to a spade lug on the passenger side of the solenoid. If your solenoid lacks this connection, it should go to a large ring lug on the lower large connection of the solenoid that goes directly to the starter. That way it should only have voltage when the starter is turning. You only want it to bypass the ballast resistor when the starter is cranking. The other end of the large wire should go the the + terminal of the coil.

I checked it for voltage with the key in the run position and it had no reading. If I check it for voltage with the starter turning over and it is hot, just connect it to the + terminal of the coil. Does this sound right?

The other reason I was thinking there was a bad ground was because when ever anything draws, (brakes, lights, wipers, etc..) the amp meter reads in the negative. If not from a ground problem, could this be from a bad alt that can't keep up with a surge when something is turned on?

thanks for all the help
tom

Originally posted by trw
I checked it for voltage with the key in the run position and it had no reading. If I check it for voltage with the starter turning over and it is hot, just connect it to the + terminal of the coil. Does this sound right?

The other reason I was thinking there was a bad ground was because when ever anything draws, (brakes, lights, wipers, etc..) the amp meter reads in the negative. If not from a ground problem, could this be from a bad alt that can't keep up with a surge when something is turned on?

thanks for all the help
tom

Yes, it is only hot when the starter motor is turning; otherwise your engine won't turn off when you turn the key off. You can test whether this helps cure your starting problem by merely "hot wiring" it by running a temporary wire from the battery + to the coil +.

The ammeter should read negative when you turn on almost anything that consumes power ONLY WHEN the alternator is not working. If the alternator is working, it should only momentarily deflect negative and then read slightly positive or zero.

Pin head!
You nailed it on the head, that was the exact problem my old F eng had. Just forgot exactly what I did to make it work.
What is the exact purpose of the black wire? Is it to bypass the alt/batt untill started,never realy understood the true meaning of it.

It bypasses the ballast resistor temporarily during starting and provides a low resistance circuit during starting so that you will get a consistent and hot spark during start up. The battery voltage drops during starting because of the large amperage required to turn the engine, so with the ballast resistor in line, the spark is iffy. You need the ballast resistor after the engine starts to prevent over saturation of the coil that would lower its life expectation. Just because it may start and can run without this wire doesn't mean it is a good idea. If it wasn't important, Toytoa wouldn't have wasted the time and expense.

I'll hook it up tonight and let you know in the morning.
thanks again
tom