BMC 1.5 electrics for starter and glow plugs

[MicB5454]

Hi, new to here!

My BMC 1.5 wiring was the original from 1979 and added to over time, I have been rewiring it as per the old system, the only alteration on the glow plugs side was removing the old busbar/fuse that was there with a single wire to the new fuse box(30 amp fuse), to ammeter there is no relay on this circuit.

Also on the starter side of things(after reading all the articles here) I'm a bit confused. Have starter battery going through switch to solenoid terminal and only have a push button to start all was fine when I tested it, now starter is completely dead help please

[Jen-in-Wellies]

30A might not be enough for the glow plugs. They are often low resistance and could blow a fuse this size. Ask me how I know!

Have you tested voltage to the starter solonoid pin when switch is on and button pressed?

[MicB5454]

There was a 30amp fuse in the original wiring and never a problem with that setup. 

Yes, the voltage was reading 13.3v

[Jen-in-Wellies]

1 minute ago, MicB5454 said:

 

Yes, the voltage was reading 13.3v

What about the return path to the battery? Earth lead from engine to where?

Is there any sort of clunk from the starter, or nothing at all?

[MicB5454]

The earth lead from engine goes back to starter battery 

There is nothing at all

For some reason I have 2 earth leads on the engine one going to leisure batteries and one going to starter is this normal?

[Tracy D'arth]

2 hours ago, MicB5454 said:

Hi, new to here!

My BMC 1.5 wiring was the original from 1979 and added to over time, I have been rewiring it as per the old system, the only alteration on the glow plugs side was removing the old busbar/fuse that was there with a single wire to the new fuse box(30 amp fuse), to ammeter there is no relay on this circuit.

Also on the starter side of things(after reading all the articles here) I'm a bit confused. Have starter battery going through switch to solenoid terminal and only have a push button to start all was fine when I tested it, now starter is completely dead help please

Is the push button just to connect the small terminal on the solenoid to a battery positive supply?

What current rating is the push button?  Solenoids draw about 12 to 15 amps. If yours is a lightweight push button it will be burnt out.

[MicB5454]

I have only had the boat a few months, looking at the push button it's a lucas was probably original to the boat so not sure on amperage, I am going to buy a tractor ignition switch in the next few days.

With 13v going to solenoid I should think switch is ok

[Tony Brooks]

2 hours ago, MicB5454 said:

The earth lead from engine goes back to starter battery 

There is nothing at all

For some reason I have 2 earth leads on the engine one going to leisure batteries and one going to starter is this normal?

 

Not normal, but it is electrically the same as linking the start and engine battery negatives at the battery end.

 

The way you describe the start circuit could mean that you are trying to switch the thick engine battery lead, rather than the thin solenoid operating one.

 

 

2 minutes ago, MicB5454 said:

I have only had the boat a few months, looking at the push button it's a lucas was probably original to the boat so not sure on amperage, I am going to buy a tractor ignition switch in the next few days.

With 13v going to solenoid I should think switch is ok

 

Are you sure that you have connected the solenoid energise wire to the correct small terminal, usually a single 6mm male blade. There is often another 6mm blade twined with a larger one on the main starter positive terminal.

[MicB5454]

Ol thanks for info on earthing.

I have a cable going from battery to a fuse box, then from fuse box to one side of switch and from switch to thin solenoid terminal 

[Tony Brooks]

Just now, MicB5454 said:

Ol thanks for info on earthing.

I have a cable going from battery to a fuse box, then from fuse box to one side of switch and from switch to thin solenoid terminal 

 

That should work, why it does not, I have no idea, unless the starter is jammed or something. Try a test cable from engien batery pos to that solenoid terminal.

[MicB5454]

Also cable from battery to master switch then to starter motor 

I will try that tomorrow, and post the outcome.

Thanks for your replies guys.

[Tony Brooks]

Would this master switch have a removable plastic key, if so they are notoriously unreliable. You could get 13V under just a voltmeter load, but apply the starter current and the voltage after the switch could drop to very low or zero.  Try putting all the wires on just one terminal as a test, thereby cutting the switch contacts out of the circuit.

[MicB5454]

Have already tried that, and that was a no go, I am wondering if moisture might have got into the solenoid as a few days ago the engine bilge had water up to the sump after 2 days of solid rain and forgot to check all cockpit covers were done up tightly, however it did start after that then just died

[Tony Brooks]

You do not mention any sounds and after a few days I doubt the solenoid armature would have rusted solid in the housing, so you should at least get a good click. I also doubt the pinion has rusted onto the shaft, so no click sounds like no electricity to the solenoid coils.

 

You also don't mention having the solenoid or solenoid cap off, so it is unlikely to be a case of the pull in coil not earthing through the motor

[MicB5454]

Having now tried a test cable direct from the battery to the solenoid there is still nothing,  no clicks, no signs of life. I suppose next step is to buy a new starter motor 

[Tony Brooks]

36 minutes ago, MicB5454 said:

Having now tried a test cable direct from the battery to the solenoid there is still nothing,  no clicks, no signs of life. I suppose next step is to buy a new starter motor 

 

Make absolutely sure that the negative (earth) for the engine is tight, clean, and in place because you should have at least got a small spark as you energised the hold in coil. You should have got an even larger spark as the pull in coil energised. Now, when working, the small terminal energises both coils. One earths inside the solenoid case and the other via the actual motor and brushes. So if the brushes were stuck, you should still have got the small hold in coil spark. Retry the cable and if you don't get any sparks it suggests the cable is not conducting (double-check the connection to the battery), the negative is not conducting, or there is something very odd with the solenoid. Check the soldering where the small blade sits on the solenoid cap, and also on the metal backing plate below the main battery cable.

 

Once you get the motor off, I would use a pair of jump leads to test it, but keep your foot firmly on it as the whole body will try to spin when/if it energises.

 

It is not too difficult to inspect the motor brushes, either a band to undo or a slightly domed end cover to remove.

 

You can also take the solenoid off, slide the body off the solenoid armature. This will tell you if the solenoid really has seized up.

 

You will feel a bit of a clot if you buy a new motor, and it makes no difference. I can't help feeling it is a wiring fault, despite the recent immersion.

 

 

 

[MicB5454]

Okay will try what you have stated but not being mechanically minded, may take me a while to figure all this out, thanks Tony 

[Tony Brooks]

Try this. It is very rough and ready but although very poor pactice should work.

 

Take your length of cable connected to the engine battery positive and lightly wipe the bared conductors on the free end across a piece of bright metal on the engine. You should get a shower of sparks. If you don't either the cable is not live or there is no earth. It would be better off it had a 12V light bulb in the cable so you limit the current. The bulb should light up. If the cable sticks to the metal, take the other end from the battery PDQ.

 

If you get a shower of sparks, then do similar on the nut/stud on the solenoid closes to the motor body. This should have a short length of cable on it running into the body or a copper strip linking the solenoid to a body terminal. If you get no sparks, then you know there is no circuit through the motor. If you do get a shower of sparks then you know there is a circuit through the motor, so any fault is likely to be in the solenoid. Then try to assess the size of spark when dabbing the cable end on and off the small solenoid terminal as I described above.

 

You can buy replacement solenoids or take the whole motor to your local autoelectrical shop for testing and/or overhaul.

[MicB5454]

I tested the pos cable to battery earth sparks fly, tested on 3 different parts of the engine and nothing, seems engine is not being earthed, as its grp cruiser how does the engine get grounded 

[bizzard]

17 minutes ago, MicB5454 said:

I tested the pos cable to battery earth sparks fly, tested on 3 different parts of the engine and nothing, seems engine is not being earthed, as its grp cruiser how does the engine get grounded 

Should be a heavy cable bolted to from the engine mass to the neg- terminal of the start battery.

[MicB5454]

I suddenly realised after I posted that last comment 

[Tony Brooks]

36 minutes ago, MicB5454 said:

I tested the pos cable to battery earth sparks fly, tested on 3 different parts of the engine and nothing, seems engine is not being earthed, as its grp cruiser how does the engine get grounded 

 

As Bizzard says, but be aware that some, if not all, 1.5 starters have what appears to be a negative stud connection on the motor end plate. Whilst it is a negative connection and can be used as the connection for the engine negative, if that is done t is all too easy to take it off and forget to put it back on. That job. stud only connects to the case, so I prefer the negative cable to run to a fixing on the engine itself, so it will only be disconnected at an engine change, or similar rarer task.

[MicB5454]

It worked I removed the earth from where it was on engine and placed it onto starter motor bolt turning over great now thank you so much for all your help with this 😀 

Yes the bolt holding the starter on to engine not o e at back of starter

[Tracy D'arth]

It must have been very badly connected to the engine or onto some very odd part of the engine.

[Tony Brooks]

1 minute ago, MicB5454 said:

It worked I removed the earth from where it was on engine and placed it onto starter motor bolt turning over great now thank you so much for all your help with this 😀 

 

That makes no sense unless you have managed to get hold of an insulated return starter, but if you have then the glow plugs, instruments and possibly the alternator may not work, so check they all do. If there is any doubt, then fit another heavy lead between the start motor earth stud and a bolt/stud on the engine.