Strange Starter Motor Issue. Please Help.

[ALLAN WARD]

We are currently anchored in a remote river in Brazil with a strange problem.
We were having dinner this evening when all of a sudden our Perkins Prima M50 starter motor started spinning without engaging the solenoid or that is what we presume is happening . I quickly cut the power supply by turning off off the master switch as there was a burning smell coming from the engine compartment at the same time . Everytime we switch on power the starter motor spins freely without engaging the solenoid .
Bear in mind that this takes place with the ignition switched off and no pressing of starter buttons .

Our problem obviously is that we cannot negoitiate the river entrance without an engine so we are pretty stranded right now until we are able to remedy this problem . Please help .

[model 10]

Are you really "stranded"? Will the engine start normally? You may have corrosion growing in/on the solenoid. Power is reaching the motor after the solenoid not before like it is supposed to.

[NoTies]

DO NOT attempt to start the engine as there is every likelihood it will stay engaged after starting, causing a melt down of the armature windings. Inspect starter motor wiring for loosed wires that might have moved and contacted solenoid output wire. If OK then remove starter and check solenoid return spring is free and springing as it should, free up with WD40 or similar if stuck. If OK, disassemble and clean solenoid contacts.

[Reefmagnet]

Two things to check. 1) the start motor positive cable hasn't shorted to the battery cable before the solenoid. I'd check that the cable hasn't come loos at the solenoid terminal and swung around and contacted the other and; 2) That the solenoid is not in fact engaging by disconnecting it's coil +ve lead.

If the contacts inside the solenoid are making the circuit, possible it's a damaged housing. Epoxy / JB Weld onboard can be used to rebuild the contact housing if you have some.

In any event, it's easy enough to jury rig something to bypass the solenoid for starting if desperate.

[Cap Erict3]

Take the starter off and examine it. Start with removing the cables. Problem will likely be obvious.


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Looking for another pretty place to work on the boat.

[undercutter]

Originally Posted by ALLAN WARD

We are currently anchored in a remote river in Brazil with a strange problem.
We were having dinner this evening when all of a sudden our Perkins Prima M50 starter motor started spinning without engaging the solenoid or that is what we presume is happening . I quickly cut the power supply by turning off off the master switch as there was a burning smell coming from the engine compartment at the same time . Everytime we switch on power the starter motor spins freely without engaging the solenoid .
Bear in mind that this takes place with the ignition switched off and no pressing of starter buttons .

Our problem obviously is that we cannot negoitiate the river entrance without an engine so we are pretty stranded right now until we are able to remedy this problem . Please help .

Power to the starter motor is supplied directly from the batteries and is only disconnected by the battery switch. A power lead then comes off the positive terminal to the ignition (starter button) switch at the engine panel which when activated provides power to the solenoid on the starter. this is then supposed to engage the bendex and also close the contact internally to the starter motor itself.

the starter motor requires replacing or rebuilding but good luck finding anywhere to get it repaired where you are.

The only suggestion(s) that I can make are

1 - with the battery switch open or off remove the negative terminal from the starter (I can't remember if they are wired this way as some starters are grounded through the case) which will prevent the starter from turning. Close the battery switch (on) and the starter should not turn. Don't confuse this lead with the main negative lead from the battery which should be connected to the engine block. Depress the ignition switch on the engine control panel and you should hear the bendex engage (you might have to listen closely near the starter to hear this. If the bendex engages have a second person then touch the negative cable from the starter to the engine block where it was connected before or anywhere else that provides a good contact on the block. Careful as the will be a large current draw and sparks will fly.

2 - If I remember correctly the solenoid on these perkins starter is internal not external which is a problem in this situation as you cannot disconnect the positive lead from the starter separately from the solenoid itself. The only other thing that I can think of would be to have someone standing by at the main engine panel with the ignition switch on and holding the starter button and then turn the battery switch on. What should happen is that the solenoid engages at the same time the starter motor starts to turn which is what normally happens when you push the starter button. When the engine starts let go of the starter button and the bendex should disengage however the starter motor will likely keep on turning. You would then have to be able to remove the main power cable from the starter itself to stop the motor from turning. I am not sure at this point whether you could just shut off the battery switch as power would be being supplied from the alternator as well. I do not believe that it would make any difference at this point whether the starter kept turning as long as the solenoid was no longer engaged. Might completely screw the starter but if there is no other way. You could also disconnect the field or exciter wire from the alternator and that way turning off the battery switch would cut power to the starter motor for sure. Option 2 may be the better way as it would certainly be safer than laying alongside the engine while it was turning.

With the battery switch off and the alternator disconnected you would not have any gauges and you would have to shut the engine down manually at the stop solenoid (usually painted red on the injector pump). Marine engines are designed to not require power to keep them running as opposed to most other land based diesels that require power to keep the fuel solenoid open.

can you post your wiring schematic?

You might also try tapping the starter with a hammer or other heavy metal object but I doubt that this will work with this starter.

I learned this lesson the hard way while in Thailand and now always have a spare starter on board.

Good luck and keep us posted.

[undercutter]

Originally Posted by Reefmagnet

Two things to check. 1) the start motor positive cable hasn't shorted to the battery cable before the solenoid. I'd check that the cable hasn't come loos at the solenoid terminal and swung around and contacted the other and; 2) That the solenoid is not in fact engaging by disconnecting it's coil +ve lead.

If the contacts inside the solenoid are making the circuit, possible it's a damaged housing. Epoxy / JB Weld onboard can be used to rebuild the contact housing if you have some.

In any event, it's easy enough to jury rig something to bypass the solenoid for starting if desperate.

I do not believe that these Perkins starters have an external solenoid. At least mine doesn't.

[ALLAN WARD]

Thanks guys!
We have found a broken wire (brown/white) at the negative relay at terminal 86. At the first attempt the starter still turned but at the second all was quiet and we were able to start the engine.

Many thanks for your suggestions and assistance, it is much appreciated!

Allan

[SkiprJohn]

Originally Posted by ALLAN WARD

Thanks guys!
We have found a broken wire (brown/white) at the negative relay at terminal 86. At the first attempt the starter still turned but at the second all was quiet and we were able to start the engine.

Many thanks for your suggestions and assistance, it is much appreciated!

Allan

That is really good news! Well done.

[Bernie10]

Originally Posted by ALLAN WARD

We are currently anchored in a remote river in Brazil with a strange problem.
We were having dinner this evening when all of a sudden our Perkins Prima M50 starter motor started spinning without engaging the solenoid or that is what we presume is happening . I quickly cut the power supply by turning off off the master switch as there was a burning smell coming from the engine compartment at the same time . Everytime we switch on power the starter motor spins freely without engaging the solenoid .
Bear in mind that this takes place with the ignition switched off and no pressing of starter buttons .

Our problem obviously is that we cannot negoitiate the river entrance without an engine so we are pretty stranded right now until we are able to remedy this problem . Please help .

I would first check the wiring on the back of your switch /starter panel to see if the switch or button if there is one hasn't shorted somewhere. Good luck whatever

[Nicholson58]

Originally Posted by NoTies

DO NOT attempt to start the engine as there is every likelihood it will stay engaged after starting, causing a melt down of the armature windings. Inspect starter motor wiring for loosed wires that might have moved and contacted solenoid output wire. If OK then remove starter and check solenoid return spring is free and springing as it should, free up with WD40 or similar if stuck. If OK, disassemble and clean solenoid contacts.

I agree - do not operate until you fix.

Disassemble and inspect. Fix the shorts, corrosion, sticking parts etc. Do not use WD40. This is goop diluted with solvents. When the solvent is gone, you are left with sticky gunk, not oil. If you want oil, use oil.

Clean out all of the moving bits and clean the contacts. If this does not solve your problem, move on to the starter switch & circuit.