Bizarre starter behavior (won't "bench test" on motor)

[suffusive]

I have a 1996 75hp Force.

I've been having hard start issues, fried OEM starter. Replaced with an Arco. Arco fires up in bench test just fine with jumper cables, however when I install on motor it will no longer "bench test". By that I mean after it's installed on the motor I run the jumper cables to the same spots directly on the starter itself (as if I were testing on a bench) and it won't do anything.

What in the WORLD could possibly cause this? Seem impossible that something is shunting current/voltage away from the starter?!? I even disconnected my main + and - motor leads to help isolate the engine and nothing changed.

 

[Chris1956]

I am not sure about Force engines, but on Mercs the starter is mounted in rubber, and needs a ground cable to the block. Do you have that setup?

 

[suffusive]

No, it directly mounts to the block without isolation. But again: I directly shorted the positive and negative cables to the starter itself while mounted to the engine (positive bolt for +, vertical threaded mounting rod for - terminal) and it WILL NOT turn over.

Basically, how could it being connected to the engine prevent a starter from bench testing?

 

[Chris1956]

Can you put a voltmeter on the positive terminal and the case of the starter (shiny metal) and see if you have 12VDC? I cannot think of any other test.

 

[suffusive]

Yes, I applied the jumper cables directly to the starter and I measured full battery voltage (~12.4V) across the terminals on the starter itself--and again, it was just sitting there doing nothing!

Also worth noting that the jumper cables didn't spark when I put them on the battery terminals.

I did sometimes manage to get some spark, and a tiny bit of movement out of the starter, if I turned the starter shaft a bit.

 

[Chris1956]

Gee, not sure what to suggest. Starter sounds broken, but you said it was new.....

 

[dingbat]

I did sometimes manage to get some spark, and a tiny bit of movement out of the starter, if I turned the starter shaft a bit.

A pair of good jumper cables will give you more that "some" spark when touched together.

How did it behave on the bench?
A good starter will about break your wrist when trying to hold on to it.

It ran on the bench because you didn't have a load on it

 

[The Force power]

Sounds like a "weak/faulty" starter and/or bad ground wire

 

[Nordin]

When you jump start on the engine, where do you connect the negativ wire?
Positive wire at the terminal at the starter and where do you connect the negative?
At the starter housing or at the engine block or where?
If you ground (negative wire) at the housing and the positive wire at the starter terminal it should spark when you touch the wire at the housing.

 

[suffusive]

I had it sitting on the ground when bench testing, didn't hold it. It jumped for sure.

I grounded the negative wire from the battery to one the vertical threaded posts that come out of the starter and bolt into the block. This same location worked just fine when bench testing the starter on the dock, but wouldn't do anything once bolted into the engine.

I'm thought this was super weird, and now I KNOW it's super weird as everyone I've discussed this with has no idea.

 

[dingbat]

I had it sitting on the ground when bench testing, didn't hold it. It jumped for sure.

I grounded the negative wire from the battery to one the vertical threaded posts that come out of the starter and bolt into the block. This same location worked just fine when bench testing the starter on the dock, but wouldn't do anything once bolted into the engine.

I'm thought this was super weird, and now I KNOW it's super weird as everyone I've discussed this with has no idea.

Have you tried turning the motor over by hand?
Perhaps the problem isn’t the starter

 

[jerryjerry05]

Jumper cables won't provide enough power to turn the starter while on the motor, unless you have #4/2/00 size wire for jumper cables.
Then the clamps need to be HEAVY DUTY too.
The battery? load test it?? Battery testers about 25$ at Harbor Freight.
That's one of the tools they sell that actually works.

 

[Grub54891]

Some cheap jumper cables are thick with insulation but have a real small wire in there. Junk.

 

[The Force power]

I'm thought this was super weird, and now I KNOW it's super weird as everyone I've discussed this with has no idea.

There's a logical explanation for it & lots of ideas to diagnose
Does the starter turn the engine with the plug out?

 

[suffusive]

The starter does NOTHING while mounted to the engine, either with the key or directly jumping it to a battery using cables ("bench testing" while mounted). That said, it's not even engaging the flywheel and therefore it's irrelevant if the plugs are in or out.

I'm not sure how jumper cables would get it to fire off the boat but would somehow be inadequate once the starter is mounted to the boat. I'm putting the voltage directly across the starter itself while on the boat, in the exact same position on the starter when I bench test it off the boat.

 

[Nordin]

If you pull the starter from the engine again and "bench test", does it run then?
Something must have happened when you mounted the starter at the engine block.
Worn brushers or bad brush springs, dirty commutator etc.
But you says it is a brand new starter.
If you connect positive wire from battery at the terminal at the starter and the negative wire to the starter housing it should turn over.

 

[The Force power]

Pull the cap & check brushers or brush springs, the contact overload

 

[suffusive]

I have pulled it off and bench tested it many times, works great. Back on boat: nada.

 

[cyclops222]

You have a open wire or a open squeezed on connector. Or loads of battery post corrosion. Need to use a voltmeter with 1 lead on 1 battery post. The other lead is moved along each wire connection until you get a jump up and dowm place.

 

[jerryjerry05]

You using the cables that came on the boat?
If so: and it still won't turn?? then the boat equipment is faulty.
Get new cables or maybe the solenoid is bad? or wired wrong?