70 Duster Starter Relay Voltages

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beep3406

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After 17 years of no starting problems I now can't start my 70 340 automatic Duster. I have looked at a lot of these threads to know how to debug this. One thing I haven't seen are what the starter relay voltages are supposed to be. Here's what I measured on mine:

Battery is 12.67V with no load. Battery is new as the 8 year old one was needing to be replaced.
With key in accessory position battery has 12.31V, BA terminal on starter relay has 12.15V, SOL terminal has 0V.
With key in starting/cranking position, battery has 12.00V, BA terminal on starter relay has 11.40V, SOL terminal has 10.92V.
Do these voltages look right? I'm not going to assume anything before I get to the starter itself. For now I get a single click out of the starter relay when trying to start it - no cranking.
Thanks.
 
hold key to start

check v at large starter terminal. if more than 10v and you get one large thunk out of solenoid, starter or solenoid is bad
 
OK, now I'm seriously stuck.
In going through things I discovered that the 40A fusible link was failing such that occasionally it would turn on the lights weakly but that's about all. So, I replaced that, thinking it was the problem but it wasn't. Tried 3 different fuses with the same results. I removed the brown/yellow wire for the NSS from the starter relay and grounded that relay terminal to the engine block. This also didn't work. I removed the ground wire from the battery to the block and cleaned it again. I don't know what gauge it is but it looks more than thick enough and has lots of copper in it. Looking really expensive to replace I simply reattached it. Again no luck getting the starter to make any noise.
So, I have a new battery with a new starter relay with new fuse and 11.4V on the starter terminal. It's got to be the starter. So, I pull out the starter and buy a new, not remanufactured, starter as Napa had it for <$100. Great. Just for fun, I take the old starter and have it tested and it passes 3 times, no problem, I saw it myself. According to the ammeter at the auto store it is pulling 85A. I haven't done anything with the new starter yet.
What am I missing on figuring out why the starter won't crank?
 
Just wondering, have you tried to turn the motor over by hand with a socket and breaker bar? Is the starter flopping around on the bolts before you lock them down? maybe bendix is getting jammed if the starter is not lined up right. Also have you measured the voltage at the starter?
 
Agree, need more info. Was this a running engine that you started having trouble with? A car you just bought and trying to crank? Have you checked the grounds?
 
With the battery fully charged and the original starter in the car put the negative voltmeter probe on a clean metal spot on the engine then:

What is the voltage with the positive meter probe on the large starter terminal from the battery with the key off?

What is the voltage with the positive meter probe on the large starter terminal from the battery with the key on in the crank position?

What is the voltage with the positive meter probe on the small starter terminal from the start relay with the key on in the crank position?

This all assumes the engine is not physically seized, that is, can be turned by hand.
 
With the new battery at 12.0v with the key in the START position, the starter is not drawing current in the car. If the engine was stuck and the starter just pulling current like crazy, the battery voltage would drop to 10 volts or so with all the current draw; it will draw much more than 85A if jammed.

Look at the battery - cable to the engine block and make sure that is very clean where it connects to the block. And then check the engine to trannie for a good ground connection and where the starter bolts into the bell housing for a good ground. I would even go to the extent of putting the old starter back in, and using one side of a jumper cable to connect directly from the battery - to the starter case and see if that helps.

BTW, taking out the starter may have unjammed something (the solenoid) or made some corrosion go away (causing a bad ground). And, the solenoid may have been jammed and not moving as noted above; it has to move to make the battery connection to the main starter windings.

By any chance do you have a separate big cable from battery + to the starter and another smaller wire to the starter relay's big lug? If so, the battery + cable to the starter may be bad.
 
340doc said:
Just wondering, have you tried to turn the motor over by hand with a socket and breaker bar? Is the starter flopping around on the bolts before you lock them down? maybe bendix is getting jammed if the starter is not lined up right. Also have you measured the voltage at the starter?
Click to expand...
I have not tried to turn the motor over by hand. The starter was not flopping around on the bolts when I removed it. I don't think anything is seized up. It didn't feel jammed when I removed it and has never previously made any unusual noises when starting.
The voltage on the starter when the ignition key is on is 11.40V.
I will try to turn it over by hand if the next few electrical attempts don't pan out.
 
SGBARRACUDA said:
Agree, need more info. Was this a running engine that you started having trouble with? A car you just bought and trying to crank? Have you checked the grounds?
Click to expand...
I've had this car for 17 years and it has been running the entire time. It has never failed to start before. Just about everything mechanical in the drivetrain is new or has been replaced.
I have checked the grounds and rechecked them, everything appears to be well grounded, but I will take another look at everything electrical.
 
Rustedwrench said:
With the battery fully charged and the original starter in the car put the negative voltmeter probe on a clean metal spot on the engine then:

What is the voltage with the positive meter probe on the large starter terminal from the battery with the key off?

What is the voltage with the positive meter probe on the large starter terminal from the battery with the key on in the crank position?

What is the voltage with the positive meter probe on the small starter terminal from the start relay with the key on in the crank position?

This all assumes the engine is not physically seized, that is, can be turned by hand.
Click to expand...

I have to put the original starter back in as neither the old nor new one is currently in the car.

My original data showed with the battery fully charged and the key in the crank position I had 11.40V on the large starter terminal. I can't find the measurement for the small starter terminal.

With the key off the large starter terminal had 12.60V on it.

Sorry for the incomplete data but I'll redo it when I put the starter back in.

Just for fun today I took data without the starter in.
Key off Large starter terminal = 12.55V, Small starter terminal 0V
Key on Large starter terminal = 12.32V, Small starter terminal = 12.00V
 
nm9stheham said:
With the new battery at 12.0v with the key in the START position, the starter is not drawing current in the car. If the engine was stuck and the starter just pulling current like crazy, the battery voltage would drop to 10 volts or so with all the current draw; it will draw much more than 85A if jammed.

Look at the battery - cable to the engine block and make sure that is very clean where it connects to the block. And then check the engine to trannie for a good ground connection and where the starter bolts into the bell housing for a good ground. I would even go to the extent of putting the old starter back in, and using one side of a jumper cable to connect directly from the battery - to the starter case and see if that helps.

BTW, taking out the starter may have unjammed something (the solenoid) or made some corrosion go away (causing a bad ground). And, the solenoid may have been jammed and not moving as noted above; it has to move to make the battery connection to the main starter windings.

By any chance do you have a separate big cable from battery + to the starter and another smaller wire to the starter relay's big lug? If so, the battery + cable to the starter may be bad.
Click to expand...

I agree that I don't think the engine is frozen. The battery voltage never drops very much when trying to start it - the load just doesn't appear to be that great. In this whole process I've never measured the battery below 12.0V.

I am sure the negative cable to the engine block is good and is making good contact. I've removed it twice and am confident in this. I have checked the engine to tranny and to one of the bolts in the bellhousing and the continuity appears good using the meter, but that's as far as I have been able to check. I did try to take the NSS out of the equation by removing the brown/yellow wire from the starter relay and grounding that terminal straight to ground. This didn't have any effect.

I am afraid I may have unjammed the starter solenoid by removing it/transporting it to the auto store.

I do have a separate big + cable but it goes to the large starter terminal while the smaller cable goes through the relay and then to the small starter terminal.

Thanks for your ideas.
 
beep3406 said:
I am afraid I may have unjammed the starter solenoid by removing it/transporting it to the auto store.

I do have a separate big + cable but it goes to the large starter terminal while the smaller cable goes through the relay and then to the small starter terminal.
Click to expand...

I would suggest putting the starter back in and seeing what happens. If it works, then either the stater solenoid is getting erratic (time to replace/rebuild the starter) or look at the separate + cable from the battery that goes direct to the starter's big lug. Put the voltmeter on the starter's big lug and try to crank if it acts up again, and see what you get: if it is at battery voltage, then the cable is good and the solenoid bad; if it drops a lot, then the cable is bad.

And if you get the same issue, then see if you can get your hand safely on the starter body when activating crank to see if you can feel the solenoid activating.

BTW, re-charge your battery; the reading of 12.32 v on the battery when in crank but with no starter in stalled looks a bit on the low side. The only real current draw is the starter relay coil and it should not pull the battery down quite that much. And in looking back at your original post and the voltages, the readings are rather low if there is no cranking action; it might be this low if the solenoid is working but not making contact, and the battery is not well charged; the solenoid pulls 14-16 amps (about the same as 4 standard headlights or dual ones on high beam).


One thing I would ask about with your readings is where the - lead of your meter is being connected; it ought to be on the battery -.
 
could it be the neutral safety sw I think if u un plug it from the relay it will disable it .have you tried jumping with a screw driver at the relay
 
dvav said:
could it be the neutral safety sw I think if u un plug it from the relay it will disable it .have you tried jumping with a screw driver at the relay
Click to expand...
I tried unplugging the NSS and then grounding the NSS terminal on the starter relay but this didn't change anything.
I have not tried jumping the relay using a screwdriver since I've always seen > 11V on the starter while trying to start the car.
 
I would still try to jump the relay just to see if it bumps the starter
 
beep3406 said:
No, I never tried this because I always see >11 V at the starter when trying to start the car.
Click to expand...

You may never have done it in the past but it's time to narrow down and hone in on your problem. If this makes the engine spin then your not getting power to the smaller solenoid wire in the crank position. Now you can work backwards from the solenoid through the switch to see why.
 
dvav said:
I would still try to jump the relay just to see if it bumps the starter
Click to expand...
It is a valid check; but the OP's point is that, with voltage showing at the starter in CRANK, the relay is working and this will not likely show anything new. But sometimes you see something different that gives another clue for diagnosis.
 
nm9stheham said:
It is a valid check; but the OP's point is that, with voltage showing at the starter in CRANK, the relay is working and this will not likely show anything new. But sometimes you see something different that gives another clue for diagnosis.
Click to expand...

But is that 12v at the large terminal(which it will always show) or 12v on the small terminal in the crank position?
 
this might not tell you anything new but might confirm in your mind

get under the car if necessary with a meter, and jumper the 2 solenoid terminals directly across. check voltage while cranking. if you have 10V (hopefully more) at the starter to the starter ground while jumpered, then you are getting enough juice to the starter.

if it won't crank then, you have either starter internal problems, or engine problems, assuming the starter gear is not jammed.
 
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