Intermittent Cranking Issue

[sanibel sailor]

Originally Posted by sailorchic34

DO NOT connect a ground to the other terminal on the solenoid. I would pull the negative cable off and clean the paint off the metal on the engine where its connected (Starter bolt??).

Also how are your batteries. Have you measured the voltage at the batteries when cranking?

The engine builder did not paint the spot where the cable attaches, nevertheless, I previously pulled it, cleaned the terminal and scruffed up the exposed metal of the block.

Battery banks are all new, 4 x 6V golf cart batts for house 2 months old and a group 27 start battery new within week. All fully charged with no loads otherwise.

[sanibel sailor]

Originally Posted by FlyingCloud1937

If you're short handed, use two jumpers with alligator clips. use the meter up by the key SW, and then the jumpers clipped down below. You can only measure voltage drop while under load.


No starter is going to crank an engine when it's only at 4 volts. It should be at a minimum of 9.5 volts while cranking. With strong batteries and high quality, properly sized cables it should be north of 10.5 volts under load.

So you either have bad bats, or bad cables some where.

What does the voltage at the battery do when cranking. If it drops to 4 volts then it's your bats.

Lloyd

Doubt it is batteries as they are all new and charged.
Could be cables, I suppose I could check resistance/Ohms although I do not know how practical that might be. Cables seem to be in good condition visibly.
Have two battery selector switches which I will take out of system and gang all the cable ends together on one bolt
I am planning on hooking a momentary switch from battery terminal on solenoid to switch terminal on solenoid, should make voltage checks much more feasible.

[sanibel sailor]

No starter is going to crank an engine when it's only at 4 volts. It should be at a minimum of 9.5 volts while cranking. With strong batteries and high quality, properly sized cables it should be north of 10.5 volts under load.


One thought is whether the starter is bad. It was just rebuilt, but is the 4 volt reading possibly a reflection of a bad starter? I was thinking it might be that the current is passing thru the starter but it is just not spinning, the low voltage reading being a reflection not of low input voltage, but a low resistance circuit thru starter to ground cable.

Part of the puzzle has to be that the starter spins GREAT when it goes, kind of makes bad batteries, cable and battery switch problems seem less likely.

[Cheechako]

So... what about matching the starter gear to the flywheel for clearance...? GM starters come with shims to accomplish this, although not often necessary. Anyone ever hear of too tight a fit on the gears on a Perkins?

[Dennis.G]

I had similar issue last summer. The intermittent part of it made diagnosis very hard. Things I did:

1. Cleaned every connection in start control and start power circuits including starter case grounding to block. No change.
2. Checked battery - was weak. Installed new battery. No change.
3. Checked heavy gauge starter cable. Saw about 12% voltage drop end to end. Replaced with new cable. No change (except that voltage drop reduced).
4. Replaced start button on temporary basis with another cheap push button up on deck. No change.
5. Took starter to rebuild shop. They cleaned commutator and brushes. Resoldered leads on rotor windings (were in poor shape). No change.
6. Temporary bypass of low current start circuit with push button at starter. Started some 20 times in a row - looking good.
7. Replaced all of the crimp-on ring connectors at solenoid, on/off switch and push button control wiring. Problem solved.

Like so many electrical problems it came down to a bad electrical connector.

Good luck - keep plugging away and you will get it fixed.

[MarkSF]

You need to focus on why you only get 4V at the starter sometimes. It's not normal, and totally unsatisfactory. I strongly suspect a bad connection somewhere in your cabling. Yes, it is perfectly possible to have an intermittent bad connection in the cabling, I have experienced it myself.

With a voltage drop like that, the bad connection is going to be getting VERY hot. I found my bad connection (at a battery post) by feeling for something hot. Be careful though, it could be hot enough to severely burn you.

[boatpoker]

Originally Posted by oldtomcat

You might have a flat spot on the starter. I drove English cars 60 years ago and they were prone yo developing flat spots. They even had a place to put a wrench to turn the starter off the flat spot and try in again.(Lucas electrics)( Charles Lucas was the prince of darkness).

Could Also be a brsh hanging now and then.

Just thoughts

OTC

Had a Jag, a Healey and a Triumph ..... English people should not be allowed to play with electricity

[MarkSF]

Lloyd has given you good advice that I want to reiterate.

The facts are :

When the fault is present, the voltage at the +ve terminal at the starter drops to 4V when cranking (or, rather, trying to crank)

4V isn't enough to crank the starter. A healthy system should give 10V at the starter when cranking.

A reading this low can't be caused by bad brushes or flat spots. I think even a totally jammed starter or engine (hydrolocked) wouldn't give a reading that low.

The possible problems are :

A very weak battery

Cabling between battery and starter that can't conduct starting current.

Lloyd suggested checking the battery voltage AT THE BATTERY when the fault is present, this will eliminate (or prove) the battery as the cause.

[sanibel sailor]

And first place award for evil bastard intermittent problem creating performance seems to be....

Battery selector switch!

No resistance between 1&2, but about 500k to 1M Ohms between them and common. Fixed with a nice 5/16 brass bolt, seems to start every time now, more quickly than before even.

I am planning on dissecting the switch for a post-mortem.

[sanibel sailor]

Autopsy showed distressingly negligible corrosion. Maybe an open contact? I hope this is the problem, it will take months of every time start to be trusting.

[sailorboy1]

replace the damn switch and stopping being paranoid