confirm that starter is the problem

F

fordmerc7

Member
’41 Mercury won’t start; nary a growl or click from the starter. Car running well when put to bed for the winter. Battery new (planned). Voltage at solenoid 6.7 at BATT side. Voltage 6.7 on starter side when button pushed – but…with cable connected to starter, voltage =0 ! Resistance from starter to any other ground point is 0.7 Ohms which I interpret as a good ground. Touching a cable from battery NEG to starter connector post has no effect (except sparks when I wasn’t quick enough). All cables are correct size.
Because removing the starter looks like a difficult task, please confirm my suspicion that the problem is the starter. If it is the starter, what can go wrong over 5 months? Any secrets for starter removal?
 
>>>Touching a cable from battery NEG to starter connector post has no effect (except sparks when I wasn’t quick enough). >>>

Well yes. Sparks would be expected. But I'd do the touching the other way around so as not to bugger up the threads on the starter posts.

If it were mine, I'd take the plugs out. Then firmly touch the cable from the starter on the negative battery terminal to see if it'll spin.

Jack E/NJ
 
I would suggest that its a bad solenoid. Sometimes they just wear out.
Had the same experience. One day it cranked over. Following day it wouldn't.
New solenoid was the cure.
To check the starter, unbolt all cables and wires that may attach to it.
Then use your battery charger or "jumper box" and attach + cable to the nut on the stater lug and touch the - cable to the starter case. Bendix should engage if starter is good.
 
If the test 19Fordy suggested does not work, one of the brushes may not be making good contact with the armature. Take off the band and check that the springs pushing the brushes in their slots have not bottomed out indicating worn out brushes. Jiggle the brushes that you can reach. It could be that the armature has worn to the point that one of the insulators separating the segments has become a high spot. If so, use a screwdriver or something to rotate the armature a few segments. If this works the problem will likely recur, and you will need to rebuild or replace the starter.
 
Your starter gear may be jammed into a worn flywheel ring gear. Put the gearshift in high gear and rock the car back and forth manually to free it if so. Always try the simple solutions first.
 
Could be something as simple as a loose/corroded battery terminal. Sometimes they'll be good enough to move a voltmeter but good enough to throw a solenoid or spin a starter.

Could be your starter switch. Some of them ground to the dash and the contacts get worn out.

I'd make sure the engine turns freely. If you have a manual transmission, put it in high gear and push the car (forward or backward or both) while somebody watches the belts/pulleys. Don't forget to release the parking brake.

If the engine is free, the next thing is to apply power from a jumper cable directly from Battery to starter terminal (bypass the solenoid). If the starter doesn't even flinch, then I'd pull it out and bench test it. If it spins, then I'd go back to the solenoid.
 
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A friend of mine just had an issue like this with his 37 truck.
Starter would spin, but not engage, I thought it was the bendix, turned out it was just a weak battery.
Could just be a connection. Or ground
 
The voltage between the solonoid terminals should show 6 volts until the button is pushed, then it should drop to zero (or close to it). This is from one big terminal to the other, not to ground. This has to be done with the starter connected.
The voltage at the starter terminal to ground should show zero until the button is pushed, then go to around 6.
Measuring the volts at the output of the solonoid with the starter cable off won't mean much - the starter load is what is causing it to mess up.
It sounds like your solonoid is bad.
 
Jim in Wisconsin said:
The voltage between the solonoid terminals should show 6 volts until the button is pushed, then it should drop to zero (or close to it). This is from one big terminal to the other, not to ground. This has to be done with the starter connected.
The voltage at the starter terminal to ground should show zero until the button is pushed, then go to around 6.
Measuring the volts at the output of the solonoid with the starter cable off won't mean much - the starter load is what is causing it to mess up.
It sounds like your solonoid is bad.
Click to expand...

I agree with this but his post sounded like he bypassed the solenoid and went directly to the starter terminal which sparked and nothing happened. The starter worked before he put the car to bed and the only thing that has happened between then and now is temperature and humidity fluctuations (I assume). Moisture and corrosion. Starter could be tired but I'd start with a few raps with a hammer...it's a free and easy test.
 
Capt Kirk said:
I agree with this but his post sounded like he bypassed the solenoid and went directly to the starter terminal which sparked and nothing happened. The starter worked before he put the car to bed and the only thing that has happened between then and now is temperature and humidity fluctuations (I assume). Moisture and corrosion. Starter could be tired but I'd start with a few raps with a hammer...it's a free and easy test.
Click to expand...
I think I've done everything suggested including the few raps, thus confirming my suspicions about the starter. Capt Kirk has my own concerns about moisture and corrosion being the culprits since I have lots of temperature and humidity fluctuations. I was just hoping for a simpler solution than removing the starter. I guess there is no easy way to do that ???
 
Were use to seeing the resistance measurements for spark plug wires, ignition modules and stuff like that, where we have an acceptable range of resistance measured in large numbers.

I'm not a starter expert but I had to take a bunch of electrical classes for my work. .7 ohms may be too much resistance in a starter. It does not sound like a lot but on a high amperage circuit it makes a huge difference. I'm not sure what the specs are on a flathead starter but I found one site that said a "Ford" starter motor should have between .02 and .04 ohms of resistance between the terminal and case.

Ohms law is used to find either voltage, amperage or resistance providing you have two out of the three measurements. Cover up the one you want to find below. Example: To find voltage multiply amperage by resistance. To find Amperage divide voltage by resistance and to find resistance divide voltage by amperage.

Voltage
_____________

Amperage X Resistance

If we use your measurements below.

6.7 Volts
_____________

Amperage Unknown X .7 Ohms of resistance

We get 6.7 volts divided by .7 ohms which gives you 9.57 amps flowing through the starter. That is not going to crank your engine.

Lets use the specification that was mentioned on another site which may or may not be correct? 6.7 volts divided by .02 Ohms of resistance and you get 335 amps. That will definitely crank your flathead. That is why it takes very little extra resistance in a high amperage circuit to cause big problems. It is so important that all your cables and connection are good. It's even more important on a 6 volt system because it takes more amperage to turn the starter than on a 12 volt system.

Like someone else said, "hit the starter with a hammer" it also helps to cuss at it while your swinging. You need to do this while someone is trying to crank the engine. A lot of times if the starter has a bad spot it will crank. If it cranks you know you have something wrong in the starter. Maybe the brushes are not making good contact? The brush springs are weak or broken. The brushes are just worn down or the armatures has a bad spot where the brushes contact. Look at the brushes first if you decide its the starter.
 
A possibly water intrusion into the cylinders ,try and get a wrench onto the crank nut .or rock the car as has been suggested and check the fan for movement ,Not your problem but I just had a situation were the starter was draining the battery on a couple of turns ,found the front starter housing was turned 180 Deg and the locating dimple was not in place .This set up a dead short ,damaged armature , Ted
 
Getting back to basics - Put a voltmeter on the starter terminal (with the other lead of the meter on a good ground) and push the botton. If you get 5 or 6 volts and the motor don't run, then the motor is bad. If you get 0 or very low volts, the motor can't run and something else is bad- probably the solonoid.
 
Battery 7 years old, didn't hold charge last year end. I thought time for a new one.
Flathead Fever's analysis is point on! 6.7 volts at batt terminal
I pulled the starter and took it to my favorite battery and starter shop.
 
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