Starter fault diagnosis help reqd

[LittleSister]

I have been wrestling with a Bukh DV10 on a recently acquired old boat. Currently it's not starting. I'd appreciate any help pointers people may be able to offer.

It has not run, so far as I am aware, for about a year.

When the engine key is turned 'on', a yellow warning light comes on quite brightly (two otehr lights don't come on). When the key is turned to 'start' a click is heard, the starter doesn't turn, but the volt meter on the engine panel plummets. (Note the click appears to come not from the area of the solenoid and starter, but a separate compartment above the engine.)

Ah! I thought, battery clapped out (it had been left uncharged a long time, and I'd recharged it but it might be past it). Tried using domestic battery from the boat (also recharged). Same result. Maybe also clapped out, I thought.

Tried a spare battery I have, which was in good knick a while ago and used to start engines fine (also recharged). Same result. So it probably isn't (but still could be) that all these batteries are duff.

I have tried turning the gear on the front of the starter, to make sure it wasn't siezed, or just stopped in a position where the brushes (?) aren't making good contact. (I assume, but don't know, this gear is fixed to the starter motor.)

Before I start dismantling the housing around engine to be able to access the wires and terminals, etc., any suggestions as to cause or approach to diagnosis.

(P.S. I haven't been able to start by hand, which I put down to lack of fitness on my part, but the engine turns OK.)

 

[NickRobinson]

Hi-
There are some quite easy tests to try but first we need to know if it is an inertia or more likely, pre engaged starter.

Does the motor have a smaller cylindrical item piggy backed on with a thick and several thinner wires? Or just a cylindrical item with one thick wire? (And possible a square ended shaft you can turn with a spanner)

Nick

 

[duncanmack]

Check your live connection at the starter and the earth connection from engine to battery.

 

[pvb]

When the engine key is turned 'on', a yellow warning light comes on quite brightly (two otehr lights don't come on). When the key is turned to 'start' a click is heard, the starter doesn't turn, but the volt meter on the engine panel plummets. (Note the click appears to come not from the area of the solenoid and starter, but a separate compartment above the engine.)

Shouldn't you start by finding out what's clicking in this "separate compartment"? To be frank, if you're not confident to follow the wiring yourself, you should ask for help from a professional. You'll get all manner of wild guesses on here, but there's no substitute for logically tracing the circuits on the boat.

 

[TQA]

Get a voltmeter and starting at the battery check the voltage. Should be 12.5 ish; get someone to turn the key for a second and see what happens. If it stays above 12 that suggests a bad connection somewhere.

Follow the leads to the starter checking at each connection. If you find a point where the meter reading drops from 12 to below 10 that is your problem.

 

[colvic987]

wondering if you have a relay in this compartment, which might have a loose/corroded or disconnected lead, which is causing the relay to click but not to power up the starter motor....

 

[fisherman]

Get a jump lead and connect the battery+ to the big terminal on the end of the starter motor, if there is sufficient power it should spin, if it has a bendix gear it should turn the engine, but not if the solenoid is the pre-engage type. If you're not confident get someone who understands to help you.

 

[VicS]

The illustrations in the owners manual appear to show a pre-engage type starter.

The fact that the voltmeter reading plummets suggests that the solenoid is operating and energising the starter motor.
You should see the pinion gear on the starter motor move into engagement with the ring gear on the flywheel.

You may have three dodgy batteries, the starter motor may be faulty or there may be a bad connection.

Start by checking ( Disconnect , clean and reconnect) all the battery wiring connections including the negative between battery and engine. Check the connections on the battery isolator switch and the main connections on the solenoid

The battery isolator switch could be faulty ... perhaps worth bypassing it.

Connect a voltmeter directly to the battery. See if the reading on the battery falls in the same way as the panel meter.

 

[VicS]

wondering if you have a relay in this compartment, which might have a loose/corroded or disconnected lead, which is causing the relay to click but not to power up the starter motor....

The wiring diagram does not show a relay in the starter circuit !

As pvb says though investigating the source of the click would be sensible

 

[Easticks28]

It is an obvious point , but I presume that the engine is not seized?

 

[Stu Jackson]

Often there is a fuse between the start button or key switch and the starter solenoid. Check this in addition to all the suggested connections. Good luck.

 

[VicS]

It is an obvious point , but I presume that the engine is not seized?

The OP says " (P.S. I haven't been able to start by hand, which I put down to lack of fitness on my part, but the engine turns OK.)"

 

[VicS]

Often there is a fuse between the start button or key switch and the starter solenoid. Check this in addition to all the suggested connections. Good luck.

Not according to the wiring diagram in the owners manual.
If there was a fuse and it had blown then the volts would not plummet as described anyway.

 

[LittleSister]

Thanks for all the suggestions (especially from those who'd actually read what I wrote!). Keep 'em coming.

FOR CLARIFICATION:

Yes, the starter has a small cyclindrical extra bit on the back with wires as described (solenoid?).

The engine voltage meter plummets and charge is lost from the battery (so I don't think it's a fuse problem, or the solenoid not powering the starter). Battery voltage measured as around 12.7v, 12.8v for all batteries before attempting start, fallen noticeably afterwards (Single handed, so haven't been able to meter the battery directly during.)

The starter is not moving or turning at all when switched on. The gear on the front end (never yet engaged with the gear on the flywheel) can be turned with a screwdriver, so this bit not rotationally siezed. Is it directly connected to the motor?

There is current going somewhere, but not resulting in movement of the starter. As I said, it is possible that all three batteries are duff, but unlikely as the third is tried and tested (though could have suddenly 'died' since last used). I am wondering about some sort of short, or could the motor be siezed and drawing current but not moving?.

I am confident with following wiring, but not familiar with starter motors and their solenoids. The wiring is at present inaccessible behind covers, and I was looking for suggestions for a 'logical approach' for tomorrow when I will be disassembling these (or possibly a 'stop messing about, your thribble-wurbler is obviously shot, get a new one' sort of answer!).

 

[VicS]

Your description of the starter and solenoid are consistent with it being a pre- engage type ( they were fitted to small diesels anyway long before they became commonplace on small petrol engines)

The solenoid does two things. It closes the electrical circuit to the starter motor. It also moves the pinion gear into engagement with the ring gear on the flywheel.

There are good explanations and some fault finding guidance on the TB-Training website http://www.tb-training.co.uk/MarineE06.html#STARTERS & CIRCUITS

without being "hands on" Id not like to say for sure whether the trouble will be a faulty ( even seized) starter motor , a duff battery or a bad connection. Pretty sure it will be one of those though.

 

[cimo]

Thanks for all the suggestions (especially from those who'd actually read what I wrote!). Keep 'em coming.

FOR CLARIFICATION:

Yes, the starter has a small cyclindrical extra bit on the back with wires as described (solenoid?).

Here's where i'd start....................
Bridge the small and large terminals on the starter solenoid with your least favourite screwdrive (expect a spark). If the motor turns, you have an electrical problem somewhere between the keyswitch and the starter solenoid.

If the motor does not turn, you have either a starter motor problem or an electrical problem somewhere between the battery terminals (chase both +ve and -ve sides of the circuit) and the motor solenoid.

(I'm assuming your proven battery is indeed good of course).
Chasing & cleaning the electrical connections is worthwhile advice regardless.

good luck.

 

[fisherman]

As Vic S says, watch out for the neg Ht lead: you can do what you like to the pos side but if the neg is poor its all rats and custard.

 

[LittleSister]

Excellent stuff, chaps, just what I needed.

Vic's post and link has greatly demystified starters for me. Cimo's given me a logical plan of action. And Fisherman has added 'all rats and custard' to my repertoire (and lined up the neg lead for some proper attention).

I'll report back on progress (he said hopefully!).

 

[LittleSister]

PROGRESS!

Pleased to report I have now confirmed the starter itself actually works.

After dismantling the covers around the engine, I decided to by-pass as much of the wiring as possible. I used car jump leads to connect my 'best' battery directly to one of the -ve ground cable terminals on the engine, and to the main +ve terminal on the solenoid. Then shorted out the big +ve terminal to the to the smaller 'switched' terminal, as suggested by various formites, and CLANK/WHIRR! - off it went!

Now retired for a cup of tea to celebrate, and will return to the fray shortly to fettle the wiring so it can be connected properly. Once I've got that sorted I can see if I can actually get the engine itself to run (which was the original task about 5 days ago!).

 

[LittleSister]

Eureka!

Managed to get the engine running using my bodged jump-lead starter set up (see previous post), then stopped it and set about tracking down the wiring problem. The wiring is a bit of a bird's nest, with some its relating to one era of Bukhs, and some to a later arrangement, plus some extra mystery wires thrown in.

It was getting too dark to see the colours properly, so I set about trying to find the not immediately apparent fuse box (there should be one fuse in the starter wire, one in another wire), rummaging around behind the engine bulkhead from the quarter berth. No luck, so I gave up and started trying to make sense of the fuel lines while I was lying there backwards and upside down.

Following one of the fuel lines I came to the back of a switch, felt round to the front of it and there was a button. Pressed it, and the starter lurched into life! (And nearly frightened the life out of me in the process!)

It would seem that the start position on the engine key has been replaced at some point (presumably having become problematic) with a start button, not on the engine switch panel, but out of immediate sight just inside the quarter berth nearby.

That still leaves one or two mysteries about the wiring, but I now have a functioning starter, starter button and engine.

Thank you all for your help. Much appreciated.