Looking for a little help with a starter issue. On the project I am building I have installed a transmission with ring gear and a starter I know is in working condition (I just removed it from the other T that it was on and started fine)and a freshly charged battery. When I check voltage passing thru the switch to the starter with the cable OFF the starter I get my 6 volts. When I tighten the cable onto the starter and check voltage with the switch in the same "crank" position I am only getting half or 1 volt. I first thought ground issue but I need some help from the good folks on here that have seen this. Thanks everyone for your help.
You have a bad connection some where. It could be one of the battery terminals, the ground strap to the frame, the connections at the starter switch, the start switch itself of the connection at the starter. Or it could be a combination of all of these. Use your volt meter and check from between each of these items. That is from the battery plus to the starter switch, across the starter switch, starter switch to the starter, from the starter case to the frame and to the battery negative. You need to have the starter switch closed (stepped on) when you check these voltages. A voltage greater than a few tenths is a problem. Short of this just take all the connections apart and clean them to a shine and make sure they are tight. If that doesn't work it may just be the starter switch or even a bad battery. good luck.
Thanks Mike. I will go thru all the connections again. Im sure it is going to turn out to me the one thing I never imagined it would be.
Dan and Mike, I wonder what size of cable you used for the starter circuit. I should be tractor or truck size for the current needed to run your starter. Is the ground wire a woven strap just throw it and use a good wire to make your ground strap. Also solder all your eyes connections, it will safe in trouble in a few years.
A quick test is to hold the starter switch down for about a minute and then feel all the terminal ends.
If one is hot enough to burn your fingers, that is the bad connection.
The next test is to measure the voltage across the battery terminals with the starter switch depressed.
If you get less than 5 volts there, your battery is weak or discharged.
If you buy new cables, they will be 2 Gauge 12 volt cables.
If you buy a new ground strap cable, it will also have a 2 Gauge rated capacity.
The original cables were 0 or Zero Gauge, which is 2 sizes larger.
The best cables are 00 or 2/0 Gauge Cables which give you 10 % better conduction.
Milt Webb’s excellent article on how to have a good 6 volt starting system using his 1925 T as an example is located at: http://milttheinstructor.com/Six-Volt_Battery_Performance.pdf It is based on his article/checklist that was in the Mar-Apr 2007 "Vintage Ford."
Note he does recommend having an addition ground to the engine / starter area.
Hap l9l5 cut off
Thanks for all the info. I am using 2 for the cable size.
I have not tested the battery with a load on it but it is the same battery I pulled off the other car to install on this one. And I was wondering about adding an additional ground strap to one of the bolts holding the starter onto the hogs head. I am hoping to get some time tonight to do some more troubleshooting. I will post the results. Thanks again.
Original Model T Ford battery cables were 1/0 gauge.
Ron the Coilman
I was thinking about trading out my braided ground, i have a 1 cable, is there much of a difference v.s. a 1/0 cable, or is this fine?..Thanks
Considering the initial starter current surge is close to 400 amps, 1 Gauge wire is not so good.
Chart.docx (13.8 k)
Not being one to give up easily, here is the chart.
Normal cranking draw is about 150-170 amps. Perhaps more on a tight engine. Locked rotor current is closer to 600 amps.
And I would not hold the starter switch down to find a short by feeling for a hot wire. That can cause some batteries to go nuclear.
Been doing some doodling while snacking...
Using the chart values for 2/0 and no.2 cable at 1000 ft. and dividing by 250 to get the resistance of a 4 foot section the 2/0 value is .0003116 ohms. The No.2 resistance is .0006252 ohms, or about 2 times.
At a draw of 170 amps the voltage losses are .0580 and .1063 volts, a difference of .0483 volts?
Where did I screw up? Is .0483 volts really significant here? Even using a 4ft. braided no.2 ground cable from the battery to the engine block would cause a voltage loss of .0966 volt.
What fakes out most people is the fact that a stock engine, with normal compression, will turn over slowly and often start with as little as 3 volts measured from the starter terminal to an engine ground.
It's not the voltage drop that is a problem. The problem is the inability of the smaller gage wire to pass current. Imagine if your garden hose was the diameter of a pencil. That is the problem. You can imagine voltage as being similar to pressure. Amperage is similar to volume of flow.
Well said Royce!
I am quoting my sophomore year electronics teacher, who was appropriately named James Watt.
Update...IT IS ALIVE!!!!!! I cleaned all connections and went and had 1 ga cables made at the local auto supply. Fresh charge, fresh gas and a few cranks and away it goes. Now just need to do some fine tuning and we should be good to go. Thanks again everyone for all of your help.