View Full Version : Electric Start Problems

CrazyKiwi - n/a
27-Feb-09, 06:12 AM
Hi all,

I bought an old cuyuna 300 twin engine to steal the electric start for my other engine combo I am working on.

The starter motor spins when you apply power but the starter cog does not move up the helix.

I have googled but not come up with anything that works.

- The bendix helix system seems well lubricated

- The rotation of the motor is definitely correct (I even tried changing the rotation)

- The bendix system works well if you remove the return spring.

As a piece of side information my electrical connections have only been via car jump start leads; might the problem be that due to poor electrical connections the starter can not develop enough inertia on the helix/ cog to overcome the tension on the return spring?

Thanks in advance for your help.



team black - n/a
27-Feb-09, 07:03 AM
Just to check the obvious, are you using the solenoid to start it? Sometimes it pre-engages the bendix

CrazyKiwi - n/a
27-Feb-09, 08:46 AM
The Solenoid?

When talking about starters people talk of 2 types of solenoid, an electro-mechanical solenoid plunger that moves the bendix or an electro-mechanical relay to carry the high currents.

Which are you refering to?

To clarify, I have had the starter to bits and there is no electro-mechanical plunger to move the bendix.

Please find attached diagrams of how I am currently Testing the bendix style starter motor and also a diagram of how I understand it should be eventually wired.

Also to confirm Team Black are you saying that simply applying power to the starter is not meant to work? What do you mean by pre-engaging the starter?

-As I am trying to test the starter at the moment;


-How I understand the correct way to connect the starter;


Thanks Again


team black - n/a
27-Feb-09, 10:29 AM
based on this I assume you don't have the sort of lump on the side of the starter solenoid then- in which case I would have thought the most likely problem is a poor contact somewhere as mentioned in your original post.

My only suggestion would be to clean the contacts and bolt the cables to their position. If this still fails, and you can borrow a clamp style ammeter, you may get some indication of whether the starter is internally high resistance.

CrazyKiwi - n/a
27-Feb-09, 06:38 PM
I havent tried to check the current it is drawing when running yet but it will be pretty high.

The resistance between the chassis of the starter and its only other terminal is real low, approx 1.5 ohms.

I might have to bite the bullet and buy another battery and wire it up for proper to test it properly.

Thanks for your help


Paul Fitz - n/a
27-Feb-09, 11:16 PM
The most likely reason for it not engaging is insufficient current. Try measuring the voltage accross the battery as the motor loads up. If it drops below 75% of open circuit voltage, the battery is shot, (assuming it is a suitable battery type). Replace the battery and try again.

If the starter is a bendix type (helical) remove all the lubrication from it and run it dry. 'Pre-engaged' starters push the cog into engagement with a solonoid before closing a switch to spin up the motor. If it is this type, remove any grease from the shaft.


CrazyKiwi - n/a
28-Feb-09, 12:18 AM
Hi, Thanks for that advice Paul

Bendix runs free, not much grease on it but alot of slipery oily residue.

I know the battery is in great condition because it starts my v6 car all the time.(Jump starting my bendix starter direct from the car)

I have another battery that I am charging at the moment and I will connect that up for proper and do your suggested current and voltage under load checks.

My temporary connection for testing has only been via a cheap set of jumper leads to my car. Electrical connection is not great.

I will keep the forum posted with my results.



jar2 - n/a
28-Feb-09, 05:03 AM
... has only been via a cheap set of jumper leads ...

I strongly suspect that is your problem - cheap lead have almost no copper (that's why they're cheap http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif ). The voltage drop across them can be very significant (especially the instantaneous drop when the starter is first turned on). You need a BIG current kick to jump the gear forward on the starter.

CrazyKiwi - n/a
28-Feb-09, 06:33 AM
I think I might connect the jumper leads to the car again and give it a couple more tries for test purposes.

My other test battery that I had planned on wiring up is stuffed so no go on that front.

I suspect you are right on the button, When I try it agin I will connect up my multimeter and set it up to work out max current and minimum voltage.

Just as an aside, when I do the proper wiring what sort of size cabling would you guys reccomend for the starter? (Obviously the shorter distance between the battery and starter the better)

Thanks again


team black - n/a
1-Mar-09, 04:30 PM
Take care measuring the current- starters can draw in excess of 90A- hence my suggestion of a clamp meter

CrazyKiwi - n/a
1-Mar-09, 05:29 PM
Thanks for the heads up.

While my auto electrical experience is near nill, my general electrical experience is good.

Thankfully I have an AC/DC Clamp that is cabable of capturing a peak current.

Yes I can imagine the 90 odd amps could just about vaporize a typical direct connect ammeter.

Thanks again


CrazyKiwi - n/a
2-Mar-09, 05:14 AM
An Update for those interested.

I gave the starter a few more jumper leads runs.

Sadly I still cant get the cog to throw up the bendix helix (but works ok when the return sprig is taken off)

The starter is detached from the motor at this stage.

My multimeter / clamp meter can capture max and min voltages and currents.

When the motor was running the current peaked at 78.5 amps and the voltage sagged to 10.14 volts.

Yes I know the voltage sag is large but the starter motor seems to run like stink.


jar2 - n/a
2-Mar-09, 07:17 AM
Couple of things:

The motor needs to be bolted to something fairly solid so that the startup torque reaction is seen by the bendix rather than the motor body. When you turn it on it should give a huge kick as it starts up - you are unlikely to be able to hold the body still during this kick.

The startup current pulse will probably be of the order of 150-200amps. If your cables are too long or not thick enough copper then the instantaneous voltage drop could be around 6 volts thus damping the motor start. Try shortening the jump cables to around 500mm or so.

And lastly - I assume you can screw the cog forward against the spring by hand? It should be pretty easy to do.

CrazyKiwi - n/a
2-Mar-09, 07:44 AM
Thanks John

Yes the cog screw foward against the spring ok.

A big 'doh' stupid me on the start torque thing, of course if the motor is free it will simply pulse and cancel a good portion of the torque on the bendix.

As a test I cut the spring to reduce the pressure against it and re-installed the starter motor back in the spare engine.

The reduced force on the spring allowed the cog to extend out properly and actually turn the ring gear.

It was a bit 'sick' though becuase it would only turn over the engine with one spark plug in. 2 spark plugs in and the compression was just too much.

This may well be because the connections on the end of the jumper leads are poor and thus not allowing a decent amount of current to flow.

Keep in mind I am only strying to start my test engine here(2 cylinder 290cc Cuyuna).

Next step, I think I'll have to save my pennies and buy another battery and wire it up on the bench for proper.

Also I gotta buy another return spring http://hovercraft.org.uk/images/icons/smiley_icons/icon_wink.gif

Will keep you posted.



ecosurveyor - n/a
5-Mar-09, 12:41 PM
Further to John's suggestion - if the motor bearings are a bit sticky - the no load current shouldn't be very big once up to speed - it may be the startup pulse given to the bendix isn't enough to throw it up the screw - these things are known as 'inertia' starters.

Assuming you are running the motor the correct way, does it apparently 'soft start' or go off with a good kick?


CrazyKiwi - n/a
5-Mar-09, 05:16 PM

I am still saving for building my electric system properly until then I wont know for sure whether we have the problem solved or not.

I have the starter bolted to the engine and it looks like the biggest problem was that a bendix starter simply cancels its own torque out when loosely running on the bench.

One other thing with this motor is that the direction of rotation is determined by internal wiring (it must be series wound) and the rotation is not dependant on the polarity of power applied to the external terminals.

Will keep you posted with new progress.