Intermittent Slow Cranking

[Mucci]

I’m trying to sort out an intermittent slow cranking issue. The car will crank fast on first try but will then slow to 1 rotation per second right before firing up. 
 

Typically, 4-5 fast cranks, then 4-5 slow cranks, then fires. 
 

Here’s what I’ve tried:

 

- New battery

- New heavier gauge battery cables

- New ground strap

- Disassembled and refreshed starter according to Mikes recommendations. (Checked bushings, lathed down commutator, cleaned and greased)

- Set ignition timing per the manual / Z ball. 
- New plugs and wires

 

 Any more ideas?

Edited June 3, 2020 by Mucci

[TobyB]

ground between engine and chassis? (Only because you don't mention it specifically)

 

Solenoid in starter?

 

t

[AustrianVespaGuy]

2 minutes ago, TobyB said:

ground between engine and chassis?

^ Most likely culprit, start here first!

[tech71]

Seems like you have done most everything to isolate this.

Have you considered the possibility that the armature(or field) copper windings are damaged?

It can happen if they overheat and the sprayed on insulation melts. Excessive cranking without allowing the starter to cool down can cause it.

You have tried so much stuff, got a spare starter you can install?

[Mucci]

42 minutes ago, TobyB said:

ground between engine and chassis? (Only because you don't mention it specifically)

 

Solenoid in starter?

 

t

 

That's the "ground strap" I mentioned replacing. The battery is in the trunk now so the strap goes from the engine to the threaded hole that other ground wires go to on the relay bracket.

 

I've also taken apart and cleaned the solenoid connections. It showed low resistance numbers on a bench test before going back in.

Edited June 3, 2020 by Mucci

[Mucci]

31 minutes ago, tech71 said:

Seems like you have done most everything to isolate this.

Have you considered the possibility that the armature(or field) copper windings are damaged?

It can happen if they overheat and the sprayed on insulation melts. Excessive cranking without allowing the starter to cool down can cause it.

You have tried so much stuff, got a spare starter you can install?

 

Unfortunately not but that's my next step. Just wanted to check if there could be something outside of the starter I'm not considering before pony-ing up for a new starter... since I've already spent so much replacing everything else.

Edited June 3, 2020 by Mucci

[Son of Marty]

Hows the battery ground in the trunk?

[Mucci]

22 minutes ago, Son of Marty said:

Hows the battery ground in the trunk?

 

To the tie down bolt for the rear seat belt.

[tech71]

7 hours ago, Mucci said:

 

Unfortunately not but that's my next step. Just wanted to check if there could be something outside of the starter I'm not considering before pony-ing up for a new starter... since I've already spent so much replacing everything else.

You could probably take it to a decent alternator/starter/electric motor and get it tested before buying a new one.

I feel your pain?

I have at least 3 of them around here, condition unknown. Too much crap laying around, you want one? 

Free to pick up near Eugene or it should fit in a Priority Mail large flat rate box for $20

Edited June 4, 2020 by tech71

[tech71]

11 minutes ago, tech71 said:

You could probably take it to a decent alternator/starter/electric motor shop and get it tested before buying a new one.

I feel your pain?

I have at least 3 of them around here, condition unknown. Too much crap laying around, you want one? 

Free to pick up near Eugene or it should fit in a Priority Mail large flat rate box for $20

 

[Healey3000]

What is the gauge of the heavier cable from the battery to the starter?  The fact that it's slowing down would usually mean a weak battery, but you have a new one.  That then makes me suspect a bad ground at the bolt, where it's heating up locally and compromising the connection.

 

I use the seat belt anchor bolt for battery ground as well.  One day, I tried to start her up and all I got was the solenoid clicking.  After some basic checks with a voltmeter, I concluded that it had to be a grounding problem and sure enough, unbolting and retorquing the seat belt bolt did the trick.  Right as rain.

 

The odd part is that I could see no reason for this.  I took the bolt out, inspected the threads in the hole, and all looked just fine.  Still a mystery.

[TobyB]

If the solenoid contacts looked clean, then maybe it's:

 

Voltmeter time!

 

Get a long chunk of wire, and hook it to the + batt terminal.

Then the meter.

 

Hook the other lead (or another long chunk) to the starter solenoid.

 

See how many millivolts (or volts) you read.  While cranking.

 

Do the same for the negative battery terminal, and the case of the starter.

 

Now do the solenoid.  You should see millivolts (maybe a volt on the positive lead) in all cases, except when the 

starter solenoid's open, when you oughta see 12v

 

Then stick it across the battery while you crank.  

Bad batteries are known to happen, even new.

 

t

 

[Mucci]

1 hour ago, tech71 said:

You could probably take it to a decent alternator/starter/electric motor and get it tested before buying a new one.

I feel your pain?

I have at least 3 of them around here, condition unknown. Too much crap laying around, you want one? 

Free to pick up near Eugene or it should fit in a Priority Mail large flat rate box for $20

 

Thanks, but if I take this thing out one more time a new one's going in

 

54 minutes ago, Healey3000 said:

What is the gauge of the heavier cable from the battery to the starter?  The fact that it's slowing down would usually mean a weak battery, but you have a new one.  That then makes me suspect a bad ground at the bolt, where it's heating up locally and compromising the connection.

 

I use the seat belt anchor bolt for battery ground as well.  One day, I tried to start her up and all I got was the solenoid clicking.  After some basic checks with a voltmeter, I concluded that it had to be a grounding problem and sure enough, unbolting and retorquing the seat belt bolt did the trick.  Right as rain.

 

The odd part is that I could see no reason for this.  I took the bolt out, inspected the threads in the hole, and all looked just fine.  Still a mystery.

 

Unfortunately this problem existed before the battery was in the trunk. I got the new battery and relocation cables to try to solve this issue. The positive cable is 0 gauge from an E36. I'll triple check but I've been making sure to sand all contact points to shiny metal before connecting things.

 

28 minutes ago, TobyB said:

If the solenoid contacts looked clean, then maybe it's:

 

Voltmeter time!

 

Get a long chunk of wire, and hook it to the + batt terminal.

Then the meter.

 

Hook the other lead (or another long chunk) to the starter solenoid.

 

See how many millivolts (or volts) you read.  While cranking.

 

Do the same for the negative battery terminal, and the case of the starter.

 

Now do the solenoid.  You should see millivolts (maybe a volt on the positive lead) in all cases, except when the 

starter solenoid's open, when you oughta see 12v

 

Then stick it across the battery while you crank.  

Bad batteries are known to happen, even new.

 

t

 

 

I'm not sure I follow. How do you crank it over if the + lead goes from battery to meter?

[Healey3000]

If that's a 2002 starter, may as well heave it into the neighbor's pool and plunk in a smaller, lighter e32 or M3 starter.  You'll never look back ?

 

What happens if you try to crank immediately after having just seen it misbehave?  Does it crank slowly or at full throat?

Edited June 4, 2020 by Healey3000

[Mucci]

4 minutes ago, Healey3000 said:

If that's a 2002 starter, may as well heave it into the neighbor's pool and plunk in a smaller, lighter e32 or M3 starter.  You'll never look back ?

 

What happens if you try to crank immediately after having just seen it misbehave?  Does it crank slowly or at full throat?

 

Are those different than an E30 M20 starter?

 

It will crank slow immediately after too.