Starter motor pinion throw adjustment (and other issues)

[David Mutch]

Hi all. Since I changed my starter solenoid, the starter has never quite worked properly. I think there may be two (or more) un-related issues, but perhaps someone will know different. It's a Lucas Starter, on a BMC 1.5. I don't know the exact model, but it's the three-hole starter.

 

Firstly, I often get the dreaded solenoid 'click' when turning the key. Sometimes this will happen quite a few times, other times the engine will crank, but very half-heartedly, and then give up, but, given enough tries, it will eventually turn over properly. The starter battery is in pretty good nick, I believe, and I don't see a huge voltage drop between battery and starter when cranking, so I don't think wiring to the starter is the issue, but haven't ruled it out completely, so would be keen to know what tests people would recommend in this regard.

 

Secondly, when the engine finally does crank, the solenoid 'machine-guns' quite loudly. Again, I don't think battery or wiring are to blame, and I have read posts elsewhere about broken wiring inside the solenoid causing it not to 'hold' when cranking (even with a supposedly brand new solenoid) but can't find any great detail on how to check/fix this.

 

Thirdly (and finally), once the engine fires up, I get a terrible gear crunching type noise, which I assume is the pinion crunching on the fly wheel. The teeth of the pinion look fine, however, and it moves very easily back and forward with no apparent stickiness, so I was wondering whether this could be something to do with needing to adjust the pinion 'throw', as the starter has an eccentric pin type adjuster. I have read some things about how to adjust this properly, but I'm not quite getting it, so was hoping someone might be able to explain it to me like I'm a five year old.

 

I have had the whole starter apart today and cleaned it out (it wasn't all that dirty, to my surprise), but this doesn't seem to have cured any of the problems.

 

All suggestions gratefully received!

 

David

​

[bigste]

My first thought is the pitch of the teeth on the pinion. You say the starter has never been quite right. Could it always have had the wrong pinion. If the pitch of the teeth do not match the fly wheel exactly you will always have problems.

[Wiltshire Moonraker]

When you had the starter apart did you check the brushes were free to move in their holders and that brush springs were pressing them in nicely?

 

One stuck brush or broken spring will make the motor draw excessive current.

 

Hope this helps.

[RLWP]

There is an adjustable pivot that 'times' the engagement of the pinion into the ring gear and the contacting of the switch in the solenoid.

 

I have been lead to believe this is a tricky thing to get right, so I always hand this over to a reconditioner. Otherwise, you get weird results - like you have

 

Richard

[Tony Brooks]

Is the solenoid on the right way round. The battery lead should fit the bolt with just a washer under it, the lead/link to the starter motor should fit onto the stud with a funny shaped metal tag under it that has a thin wire soldered into it.

 

If the solenoid cap has been taken off is it back on the right way round? The twin thick and thin wire should go to the small terminal. The single thin wire should go the the "funny shaped" tag above.

 

I do not have the exact adjustment for the throw but but with just the small (6 or 9 mm blade) terminal energised at 6 volts there should be a very small gap between the pinion and end bracket. If the pinion is hitting the bracket it may not move enough to properly close the solenoid contacts.

 

Check the voltdrop between battery and the small terminal. Undersized wiring or a faulty ignition switch can cause some of your symptoms

 

I can not explain the grinding noise unless its the pinion sprag clutch slipping but certainly make sure you have the correct pinion. Also check ALL the flywheel teeth. They normally only wear/burr in two small areas.

[RLWP]

I can not explain the grinding noise

 

Machine gunning could be a flat battery

 

Richard

[Tony Brooks]

 

Machine gunning could be a flat battery

 

Richard

 

Agreed, usually the most likely - or dirty battery connections but the OP suggests the battery is OK and if he has measured to starter circuit voltdrop I assume he has measured the cranking voltage.

 

If the OP has not perhaps he could post the cranking voltgae at the battery clamps AND on the lead posts.

[David Mutch]

My first thought is the pitch of the teeth on the pinion. You say the starter has never been quite right. Could it always have had the wrong pinion. If the pitch of the teeth do not match the fly wheel exactly you will always have problems.

Thanks. Sorry, I meant that it hasn't been right since I changed the solenoid. Before that it worked fine (until the solenoid got stood on and broken)

When you had the starter apart did you check the brushes were free to move in their holders and that brush springs were pressing them in nicely?

 

One stuck brush or broken spring will make the motor draw excessive current.

 

Hope this helps.

 

Cheers. That was my first thought, but the brushes look nearly new and the springs are strong (I can vouch for that having had to prise the b***ers off a couple of times!) They weren't even particularly dirty

[Tony Brooks]

Thanks. Sorry, I meant that it hasn't been right since I changed the solenoid. Before that it worked fine (until the solenoid got stood on and broken)

 

Cheers. That was my first thought, but the brushes look nearly new and the springs are strong (I can vouch for that having had to prise the b***ers off a couple of times!) They weren't even particularly dirty

 

Good chance its on upside down then.

 

Only the hold in coil will be working.

Edited June 11, 2016 by Tony Brooks

[David Mutch]

 

Agreed, usually the most likely - or dirty battery connections but the OP suggests the battery is OK and if he has measured to starter circuit voltdrop I assume he has measured the cranking voltage.

 

If the OP has not perhaps he could post the cranking voltgae at the battery clamps AND on the lead posts.

 

Thanks Tony. I will check everything you have suggested and report back. Not sure how I will get hold of a 6v power source. What kind of current would it have to be able to supply?

[Tony Brooks]

 

Thanks Tony. I will check everything you have suggested and report back. Not sure how I will get hold of a 6v power source. What kind of current would it have to be able to supply?

 

The reason they said 6 volts was to reduce the current that will flow through the pull in coil because it will not "turn off" as it does normally. Use 12V but be very quick.

 

However with the last bit of info I think that if you kept the same solenoid armature the adjustment is probably OK. Please check the solder pads on teh solenoid cap. The one on the small control terminal should have two wires in it, the one on the other side should have one but remember what I said about fitting the solenoid upside down.

[Sir Nibble]

I think Tony has this one in hand, my first thought was solenoid upside down too. For the adjustment, what I do is power up the solenoid before the link from solenoid to motor is fitted and "Flash" the solenoid motor terminal to earth in order to momentarily power the pull in coil and leave the pinion extended on the hold in coil alone. Correct clearance is 0.025".

[Tony Brooks]

Thanks SirN, No. 1 tip

[Sir Nibble]

There is an adjustable pivot that 'times' the engagement of the pinion into the ring gear and the contacting of the switch in the solenoid.

 

I have been lead to believe this is a tricky thing to get right, so I always hand this over to a reconditioner. Otherwise, you get weird results - like you have

 

Richard

The actual purpose of this small clearance is so that when the pinion is driven along the spiral splines hard against the stop collar by the motor torque, the engagement fork is unloaded and theoretically should float between the pinion flanges without rubbing occurring between rotating and stationary ironmongery. All starters have some form of spring linkage to allow the solenoid to complete it's travel if the pinion is baulked, for instance contacting the ringear tooth to tooth. In this case it's done by a spring loaded plunger within the solenoid armature.

[RLWP]

The actual purpose of this small clearance is so that when the pinion is driven along the spiral splines hard against the stop collar by the motor torque, the engagement fork is unloaded and theoretically should float between the pinion flanges without rubbing occurring between rotating and stationary ironmongery. All starters have some form of spring linkage to allow the solenoid to complete it's travel if the pinion is baulked, for instance contacting the ringear tooth to tooth. In this case it's done by a spring loaded plunger within the solenoid armature.

 

That makes sense, otherwise you are introducing unnecessary wear on the fork

 

Thanks Snibs - I shall continue to pass starters onto specialists, I have enough to do as it is!

 

Richard

[David Mutch]

Thanks once again all. As soon as it stops raining I'll have a go at all that!

[David Mutch]

Thanks once again all. As soon as it stops raining I'll have a go at all that!

[David Mutch]

Hi again all. Well, it's stopped raining for five minutes, so I got the starter off and decided to have another look. So far as I can tell from all your descriptions, the solenoid is the right way up! However, when I came to test the pinion throw, the pinion was going nowhere near the end of its travel (nearly an inch short). This made me suspicious, so I took the thing apart, and it turns out that the armature was in the wrong way round! It must have been like that for years, and never caused a problem before I changed the solenoid! Anyway, I turned it the right way round, and have managed to set the throw to the correct clearance, as far as I can tell.

 

I haven't tested it yet, because before I did, I wanted to positively identify all of the connections on the solenoid, to make sure that the other problems aren't being caused by incorrect wiring. I'm pretty sure I've correctly identified the terminals for the cable from the battery and the link to the motor, but there are two spade terminals on the solenoid, only one of which is normally in use. The soldered terminal in the attached picture is the one to which the wire from the ignition is usually attached; the one that is attached with a nut is usually redundant. Is this right? If so, what is the second terminal for? I have searched Google, but haven't been able to get a definitive answer to this one.

 

Thanks in advance for your assistance!

 

 

[Tony Brooks]

Hi again all. Well, it's stopped raining for five minutes, so I got the starter off and decided to have another look. So far as I can tell from all your descriptions, the solenoid is the right way up! However, when I came to test the pinion throw, the pinion was going nowhere near the end of its travel (nearly an inch short). This made me suspicious, so I took the thing apart, and it turns out that the armature was in the wrong way round! It must have been like that for years, and never caused a problem before I changed the solenoid! Anyway, I turned it the right way round, and have managed to set the throw to the correct clearance, as far as I can tell.

 

I haven't tested it yet, because before I did, I wanted to positively identify all of the connections on the solenoid, to make sure that the other problems aren't being caused by incorrect wiring. I'm pretty sure I've correctly identified the terminals for the cable from the battery and the link to the motor, but there are two spade terminals on the solenoid, only one of which is normally in use. The soldered terminal in the attached picture is the one to which the wire from the ignition is usually attached; the one that is attached with a nut is usually redundant. Is this right? If so, what is the second terminal for? I have searched Google, but haven't been able to get a definitive answer to this one.

 

Thanks in advance for your assistance!

 

DSC_0240.JPG

 

 

Can't see the photo but any blade terminal on a bolt type connection can be ignored. The one with the solder pad, often but not always a 6mm one, is the one that should have two wires soldered into its pad. I think the answer is yes.

 

What I can not understand is how the solenoid armature could be put in backwards, it has a sort of eye think on the fork end but if that's what you found it should now be OK.

[David Mutch]

 

 

Can't see the photo but any blade terminal on a bolt type connection can be ignored. The one with the solder pad, often but not always a 6mm one, is the one that should have two wires soldered into its pad. I think the answer is yes.

 

What I can not understand is how the solenoid armature could be put in backwards, it has a sort of eye think on the fork end but if that's what you found it should now be OK.

 

Thanks Tony. I see that the photo hasn't worked. Not sure what's gone wrong there.

 

The armature has an angle in the middle (where the pin goes through it) of about 10 degrees, so when it is put on the pin with the bend facing away from the solenoid, it cannot travel far enough to engage the pinion properly. Turned 180 degrees along its axis of symmetry (i.e. not swapping the large and small end forks, which you couldn't do, but simply rolling it, so the pin goes through the pivot point from the other side) it starts that 10 degrees further pulled in, and so can now reach the end of its travel when the solenoid pulls in (if that makes any sense.)

 

Right, I shall go and hook it back up and see if that's solved the problem!

[Tony Brooks]

The lower blade is the one connected to the ignition switch.

 

The only think I can think the other blade is for is to feed ballast resistor coil but why a diesel starter needs one is beyond me. SirN may comment further.

 

The solenoid seem to be correctly fitted, I am sure\all should be well now.

[David Mutch]

The lower blade is the one connected to the ignition switch.

 

The only think I can think the other blade is for is to feed ballast resistor coil but why a diesel starter needs one is beyond me. SirN may comment further.

 

The solenoid seem to be correctly fitted, I am sure\all should be well now.

 

Thanks tony. Well, the change to the armature seems to have resolved the machine-gunning and the crunching gears noise! However, the solenoid is still clicking, and the engine cranking somewhat lazily a few times before eventually turning over normally.

 

I have run the multimeter over the ignition circuit and this is what I get:

 

Starter battery resting voltage: 12.9v

Cranking voltage on battery posts: 11.2v

Cranking voltage on battery clamps: 11.2v

Voltage drop between starter battery +ve and battery lead terminal on solenoid: 0.17v

 

Now, here's the bit I don't understand, and which makes me suspect something is very wrong around the ignition switch area. The ignition switch terminal on the solenoid appears to be earthed. That is, I appear to get 12.9v between it and the +ve side of the starter battery. When cranking, this drops to about 8v. Conversely, I get 0v between the terminal and earth, which rises to around 2.5v when cranking. This seems bizarre to me, as I had assumed that it was simply a switched +ve, earthed through the starter body to the engine/hull (I supplied 12v from the +ve when testing the pinion throw, and this worked just fine.) What readings should I be getting here?

 

Anyway, I tried replacing all of the spade connectors, and got the same result. So, I tried bypassing the ignition wire, using another wire - known to be good - between the ignition switch and the solenoid. Same result. I am a bit stumped now as to what to try next. What's weird is that this setup was all working perfectly well until I changed the solenoid, with no other changes to wiring!

[David Mutch]

I think Tony has this one in hand, my first thought was solenoid upside down too. For the adjustment, what I do is power up the solenoid before the link from solenoid to motor is fitted and "Flash" the solenoid motor terminal to earth in order to momentarily power the pull in coil and leave the pinion extended on the hold in coil alone. Correct clearance is 0.025"

 

A special thanks to you, by the way, Sir Nibble, for this. Worked a treat!

[Sir Nibble]

Your voltage readings make complete sense and are fine, except you are evidently losing some on the solenoid feed, probably the switch. I strongly suspect a volt drop and the one place you don't seem to have checked is battery -ve to starter body.

The extra terminal is a ballast ignition terminal as Tony surmised and is only there because it no longer makes sense to make solenoid caps without it.

[bizzard]

A fairly hefty relay switch close to the starter is a good plan to relieve the starter button-key switch of the load and possible volt drop through the wire. I use an old type stand alone car starter solenoid for the purpose, as quite a few boats do.