85 brat weak crank , good battery, clean terminals

[mkoch]

My 85 Brat started and ran a month ago, then it sat for a month.

I tried to start it, the engine would maybe 1/2 turn over with each try.

Things I did

Replace battery with  a proven strong one.

Clean battery terminals, and cable clamps, clean engine ground connection, clean positive cable connection at starter.

I can swap parts with my healthy 1984 GL!

What should my next step be?

 

 

 

Edited May 5, 2020 by mkoch
typo

[Step-a-toe]

I find corrosion can travel down the aluminium power cable strands.

Swap starter??

[Scoby4wd]

I had a problem where my starter would just click sometimes and not start.

Ended up installing a 12v relay to the  starter signal wire then pulling power off the batter and sending that to the starter via the relay.  Fixed my issue.

[DaveT]

I never had a starter do that, but known good battery takes away #1 thing.
click no crank is fixed by adding the relay, but I never had weak crank due to the problem that causes click no crank.

Worn out contacts on the starter solenoid typically makes a louder intermittent click no crank.  I suppose it could get flaky other ways though.  I'd take a look at those.

 

[idosubaru]

On 5/5/2020 at 12:21 AM, mkoch said:

My 85 Brat started and ran a month ago, then it sat for a month.

I tried to start it, the engine would maybe 1/2 turn over with each try.

Things I did

Replace battery with  a proven strong one.

Clean battery terminals, and cable clamps, clean engine ground connection, clean positive cable connection at starter.

I can swap parts with my healthy 1984 GL!

What should my next step be?

 

 

 

Test for voltage at battery posts (not clamps)

Test for voltage at battery cables (as far back as metal is showing from the posts....clamps, crimp, exposed wire)

Test for voltage at starter. 

How close are all those three measurements? 

Starter needs lots of amps so voltage doesn't tell all the story, but it's a good start to know how much voltage drop you're getting at each of those points.

[mkoch]

we Problem solved, thank you for the advice!

The problem was a hokey dash mounted aftermarket starter switch.

The switch is a rotational one, which breaks contact when the knob is rotated beyond the start position.  The problem is, the switch has a fussy approx. 5 degrees of contact in “start” position.

 

 

[Step-a-toe]

An emergency fix where a relay may have done the job

[mkoch]

Update!

I swapped the starter with my ‘84 GL.

Success!   The engine now turns over with gusto.

The old starter just did not have the power (torque?) to do the job.

Is it common for a starter motor to go to 30% power?   I thought  they just failed outright.

Edited May 8, 2020 by mkoch

[DaveT]

I have not had one do that.  Maybe 1 brush wore out, or broke / stuck.  Forgot if these have 2 or 4 brushes.

[NV Zeno]

It's not often starters fail that way, but not unprecedented.  The starter on one of my Fords failed like that.  Glad you found the problem and got it fixed!

And, thanks for the update..that's very helpful.

Edited May 8, 2020 by NV Zeno
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