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Starter Problems

jaymalyon

New member
Hey guys,
I'm working on a 1990 Shamrock with a 351 in it and I'm at a loss with the starter. I originally replaced it because it was seized up from not being used for about 4 years. So bought a new Sierra #18-5920 and installed it. The new starter will turn the engine over BUT there was a good bit of electrical looking smoke and a spark coming off a terminal when I cranked it. NOT GOOD. So I started checking all my connections with my power probe and here's the problem, the terminal where my yellow / red tracer wire (Ignition) connects to the starter is reading as a ground. This is with only my main 12V wire connected. If I leave the ignition wire disconnected and turn the key, the wire reads 12v when it receives the signal. So for whatever reason, I've got a 12-volt signal going straight to a ground that should be a circuit that pops the starter. I'm lost.
 
the yellow/red wire should be the START circuit, from the key switch back to the solenoid....how did you determine that circuit was reading as a 'ground'?

where did the smoke originate from? did you verify the high current carrying conductors were in good (electrical) condition?
 
the yellow/red wire should be the START circuit, from the key switch back to the solenoid....how did you determine that circuit was reading as a 'ground'?

where did the smoke originate from? did you verify the high current carrying conductors were in good (electrical) condition?


Yes, the yellow/red is the start circuit. I've got continuity from the terminal at the starter solenoid all the way to the key.

From what I could see, the smoke was coming from the starter.

The start circuit terminal on the starter solenoid, not the yellow/red wire, is reading as a ground with my power probe/ test light/ multimeter.

Yes, the heavy gauge 12-volt wire is in good shape.
 
..... start circuit terminal on the starter solenoid ... is reading as a ground with my power probe/ test light/ multimeter....

if this means the terminal from the solenoid to the starter motor, that isn't unusual, for most testers are very low current devices. What you are seeing in the 'resistance' of the start motor....you can verify this by disconnecting the short lead going to the motor, from the solenoid.

As far as the smoke goes, that usually indicates something not good in the starter motor....I'd be inclined to ask for another one....Sierra's quality control isn't what is used to be, sad to say....
 
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Hey guys,
I'm working on a 1990 Shamrock with a 351 in it and I'm at a loss with the starter. I originally replaced it because it was seized up from not being used for about 4 years. So bought a new Sierra #18-5920 and installed it.
In my opinion, you'd be better off with a Marine approved HTGR/PMGR starter motor.

Ford HTGR PMGR starter motor.jpg


The new starter will turn the engine over BUT there was a good bit of electrical looking smoke and a spark coming off a terminal when I cranked it. NOT GOOD. So I started checking all my connections with my power probe and here's the problem, the terminal where my yellow / red tracer wire (Ignition) connects to the starter is reading as a ground.
What you're reading is the resistance of the electro-magnetic coil unit within the solenoid unit.

This is with only my main 12V Cable connected.

If I leave the ignition wire disconnected and turn the key, the wire reads 12v when it receives the signal.
That is not an ignition circuit.
As Mark mentioned, that is the starter motor's S terminal circuit (yellow/red strip wire).
S = solenoid!


So for whatever reason, I've got a 12-volt signal going straight to a ground that should be a circuit that pops the starter. I'm lost.
As the S circuit is energized, the electro-magnetic coil becomes energized. You will see a load while energize.
As the coil becomes energized, it pulls the plunger.
The plunger (via internal actuator arm) kicks the pinion gear into the flywheel ring gear as it simultaneously closes the main armature contacts.
Once the main contacts close, the armature should spin........ but only if the main Positive battery cable is connected correctly, and only if the starter motor chassis has a good System Negative Common connection.


Here's an old School Non-gear reduction solenoid style starter motor.
(pinion gear is 1 to 1 with armature)

Starter motor.jpg




Two styles of HTGR/PMGR starter motors
HTGR = high torque gear reduction
PMGR = permanent magnet gear reduction.

(pinion gear is approx 1 to 3 with armature, creating more torque to flywheel)

GM examples only.... not same as Ford!


Starter motors  planetary vs spur gears.jpg



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I believe I have narrowed it down to yet another faulty new part. This is the second new Sierra starter I have installed this year that has malfunctioned. Waiting on a warranty replacement now. The starter I originally removed earlier this year was an Arco. Any reason to think that brand will be any better?
 
I believe I have narrowed it down to yet another faulty new part. This is the second new Sierra starter I have installed this year that has malfunctioned. Waiting on a warranty replacement now. The starter I originally removed earlier this year was an Arco. Any reason to think that brand will be any better?

HTGR/PMGR planetary gear reduction motors are intrinsically OK.... but some brands incorporate a nylon ring gear. The nylon gear will eventually fail.

HTGR/PMGR spur gear reduction motors will use all steel reduction gears.

Starter motors  planetary vs spur gears 2.jpg




One of the problems is..... most suppliers (of the planetary style motors) are not able to tell you if their unit incorporates a nylon gear or a steel gear. When asked, they give us that "deer in the head lights" look!

Starter motors  planetary vs spur gears deer in the head lights .jpg


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