One for the technical gurus if you can help.

When starting, quite often, the starter motor refuses to engage with the fly wheel, instead making a rather unhealthy rattling sound which I assume is the starting dog rattling against the ring gear. Second or third attempt it finds a gap between the teeth and it roars into life.

I have been advised that I need to take a file to the teeth on the dog gear of the starter motor and put some points back on them. My question is, does this sound like good advice, complete cobblers or something in between? Could there be something else wrong? I don't want to take the starter motor out to find there is nothing wrong with it.

All ideas gratefully received.

My bus number (if any): RM1013

Take the motor off and get it overhauled. To continue running it like that will damage the flywheel ring gear.

It could be the switching mechanism inside the starter is out of adjustment. I had this with my GS for years and it wore out the ring gear in 3 places. Eventually I had to fit a new ring gear. Luckily someone in Devon had some, but I know he has none for the AECs.

There is a good chance the starter will fail on the road so you'll end up with an expensive tow job. To keep running with such a problem is false economy.

I have just the same problem gentlemen so this is very helpful. A local commercial (truck) mechanic had a look at it and couldn't find any problem .... what a great asset it must be to have a Routemaster expert nearby!!

My bus number (if any): RM2302

Make sure that the flywheel ring gear is not already damaged before refitting the starter motor, otherwise the replacement starter won't last long. Fortunately the ring gear on all RMs with a Wilson gearbox could hardly be any easier to see.

starter motors are not cheap to have overhauled. The Lucas type as fitted to AEC/Leyland/Gardner engines are about £280 (cheaper places are available), Cummins etc about £380 or more. I don't have one on the shelf, my last Lucas one went on an RT last year and I haven't had time or money to get that rebuilt yet.

I do have a new overhauled unit for an Iveco engine.

My bus number (if any): RML2532

Thanks for the advice. I'll report what I find once I get the starter motor out.

My bus number (if any): RM1013

Interesting to read this thread, as last weekend the starter on my RM did cough a little when starting not strangey from cold but an hour later. It last did this in September near the end of the day after working hard. Not knowing when someone had there greasey fingers over this unit, perhaps even back in LT days back in the 80's. (Still steam driven with an AEC and a dynamo by the way..) Perhaps the time is near to have it rebuilt/checked? Rather than a costly tow from the roadside.

My bus number (if any): RM158

It seems to be catching. I tried to start RML2302 yesterday and I got the same problem again - a couple of coughs, a rattley noise then nothing apart from some clicking relays/solenoids. In the past it has been cured by moving the flywheel round with a heel but this is obviously not a solution. As mentioned above a local truck mechanic could find no obvious problem but clearly something must be amiss. Need to be able to get underneath and look at it properly...

My bus number (if any): RM2302

I wonder if Hugo is able to tell us if he has solved this problem please? I haven't yet been able to establish what is happening with mine.

My bus number (if any): RML2302

Without inspecting the bus it's going to be difficult to diagnose if you've tried what was suggested above.

Hi Roy - yes, you're right of course - I haven't even been able to establish if the cogs on the starter are trying to engage with the flywheel (not possible to do without someone working the start switch while you're under the bus, which I don't really fancy (although you may know otherwise)). The connection to the end
of the body looked loose and rusty - there is a serrated vibration washer which didn't look as if it was doing its job but I didn't have any tools with me to tightened it. Batteries are fully charged. The real answer of course is to check the operation with someone else - perhaps using a mirror (I haven't got a pit or ramp)and to take it off if it isn't engaging. It only seemed to have two securing nuts - if there is a third above the motor that looks very hard to reach.

Anyway,the point of my post was to see if Hugo had got a replacement and everything was now fine but thanks for the reply - I will get to grips with what is happening

My bus number (if any): RML2302

I don't think we established what engine your bus has.

Brian's bus has a Cummins C series.

Thanks Roys! The starter seems to be the CAV S115 pattern (see image on Google - and apparently reasonable price @ http://shop.startermotorsalternators.com/cummins-c-seriesfoden-3000-series-cav-s115-24-22--starter-motor-123-p.asp#.UYe6b7WTjSg

My bus number (if any): RML2302

Change the starter is the easy solution. Make sure you isolate the electrics forts. Relove the big connecting cables; remo9ve the 3 (?) smaller wires; there's 3 bolts that go round the flange, they're a right pig to get at, but with a 1/2" long socket extension ans ISTR a 16mm socket, they sould be accessible. the starter is also a pig to get out as it has to swivel round the downpipe and work round the "boat" to come out. I done mine with the bus on liftfs which makes life a lot easire. If you have access to a pit it makes things easier.

What you have is a common fault on the Cummins engines. Water drips down into the connection on top of the starter body and corrodes it; this causes a bad connection for the initial bit of the solenoid which causes the problem. Having said that, have you made sure the pinion slides freely? With the elctrics OFF, go under the bus and try to pull thepinion out with a lever; when it's out, a good squirt with WD40. Also check your battery isolator terminals; mine were rusty and one connection was loose.

I've had all these problems; changed the starter; secured the isolator switch; removed, stripped and cleaned the isolator switch. That solve the problem for a while, then it came back. the bus would start with the boost pack on; I then found a dud battery so changed that and problem solved. then the problem came back; changed the other 3 batteries last weekend, problem solved again. The batteries were less than 4 years oild, type 721 from a reputable supplier!

Even us "experts" get baffled sometimes.

That's great Roy, thank you very much - very helpful, particularly the detailed instructions!

My bus number (if any): RML2302

Following the advice of the two Roys I'm very pleased with myself having had great success this morning towards getting my starter motor out, although ultimately I have gone for the method of taking up the rear cab floor panel (very easy) so as to get much easier access to top nut, in the absence of a pit. The problem seems to be a rusted and burnt out loose terminal on the end of the barrel (protective rubber cover not in place naturally).

For the moment I've fallen at the final hurdle however because I can't get the motor off the three studs, which are moderately rusty. I wonder if either/both of the Roys, or anyone else have any tips on how to release it please - fine blade screwdriver, rubber hammer .....? I've sprayed some penetrating oil on the studs for the moment. Thanks in anticipation.

Brian

My bus number (if any): RML2302

It's surprising how comparatively easy it is to get sections of floor out of the way.

Yes Rubber hammer on solid part of body. Then you'll probably find that it tests out OK on the bench because you've been hitting it.

Thanks Roy - I knew you'd know the answer! Ever thought of moving to beautiful North Yorkshire ..... ?!

My bus number (if any): RML2302

Ta-dah!! Tap,tap,tap - jiggle,jiggle,jiggle - motor drops (gently) between the boat and steering crossmember on to my chest! The sense of achievement was great - easypeasy for you chaps but really the first bit of serious mechanical bus work I've done (age 63) as a lawyer who always wanted to be a bus driver. I carried it home like a prize fish.... Thank you gentlemen!

PS It turns out to be a Prestolite, refurbished by the esteemed J & S Components

My bus number (if any): RML2302

Well done! It's never easy on a Cummins. ISTR having to remove the downpipe to get mine off!!

J&S Electrical are no longer in existence, but PSV Electrical at Hoddesdon keep these in stock, though your local auto electrical supplier ought to be able to repair and refurbish your machine. It'll take a bit more effort to put it back as you have gravity as an enemy, hehehe.

Thanks RTB - the "well done" is appreciated! I look forward to defying gravity, although I think I might be able to drop it in from above. I was recommended to take it to a local chap on a farm near here on the fringe of the North York Moors who has been working on bus and tractor starters for the last 30 years -I'm confident he's going to do a careful and inexpensive job ("by the end of the week" he says).... not sure if he will be able to crimp on the replacement connectors that will be needed however

My bus number (if any): RML2302

Chaps,

Sorry not to have replied earlier. I had to take a bit of an enforced break but I'm back at it and addressing once again the starter motor. Sadly, no, I haven't fixed it yet.

I'm convinced that the starter motor itself is in good nick. If you are a fan of 'elf and safety perhaps don't read the next bit but; I tested the idea by manually engaging the dog into the ring-gear and preventing it from returning with the aid of a paint stirrer stick then employing a glamorous assistant to pull the starter hook, removing the stick swiftly once everything started moving. Started every time. I'm happy that the motor is doing the business, it's the dog throwing forward into the ring gear that is not going to plan.

I can highly commend the suggestion of getting someone else to pull the switch so that you can actually have a good look at what the bits are doing. It all happens quite quickly but it looks to me like the dog gear is starting to rotate by itself before it is thrown forward into the ring gear thus it is like trying to get a car into first gear without using the clutch.

The dog slides quite freely on the spigot but not as freely as on my spare Land rover starter motor. Does that sound about right?

Second question, on the BMC starters that I'm used to the dog teeth have a distinct 45 degree bevel on each side to help them locate into the ring gear. On the bus gear they look square. Is that because they didn't have a bevel or have they worn down that far already?

Third question, the dog is kept on the motor spigot with a castlated nut and split pin. It worries me that the castaletd nut looks like it was home made from a regular nut, is this a bodge or just a funny supplier of nuts to LT.

Final question, there is a second thin nut on the spigot (sorry I should have taken a photo of this). It looks like a lock nut, although that function is rather taken care of by the split pin, or it could be working as a spacer. How much clearance should there be between the dog gear and the ring gear when the starter is not engaged? At the moment it has to travel about 1/8th inch which seems to me a bit far.

Many thanks for advice so far and further ideas gratefully received. I'll happily post any progress.

Hugo.

My bus number (if any): RM1013

the starter dog will spin as soon as you pull the starter switch, but will not go at full power until it has engaged with the flywheel. when it moved fully forward, it makes another contact inside the motor which gives full power. If the dog isn't engaging you'll never get full power to turn the engine.

1/8" clearance sounds about right. I'd suggest you take the motor off and get it rebuilt. the last thing you want is a serious electrical fault burning your bus out.

The castle nut and lock nut on the spigot are left hand thread.

My bus number (if any): RML2532

So we continue to tackle the issue.

Taking the wise words of these pages to heart we have had the starter motor off and away to the repair man. He reported back that the insides of the motor, brushes etc. are as good as the day they left the factory, it was bench tested and returned with a clean bill of health.

We refitted the motor, which I have to say was a surprisingly easy operation, and first pull of the hook all went perfectly. Sadly, with the temperature several degrees below zero not many cylinders wanted to fire and the engine spluttered to a halt. Second pull of the hook and the dreaded clattery noise and refusal to engage is back. Hmmm.

Our repair man did suggest that it is important that the motor gets a good dose of current from the starter switch wire (the thin blue one labeled H4 in our case). It is entirely within the bounds of possibility that the wire has fatigued at the terminal end or somewhere else and is hanging on by a final strand. I'll be checking this tomorrow to see if that is the cause.

Interested to hear if others have come across this.

I hope I can report positive news by the weekend.

My bus number (if any): RM1013

You need to check the very thick cables that run from the battery. I have the same problem with my Cummins RML. sometimes it's fine, other times not. My problem is with the leads from the battery to the isolator. It starts first time every time with the boot pack plugged into the cow bell socket, and I have a new set of batteries and a new starter!

My bus number (if any): RML2532

Thanks Roy.

Excuse the amateur question but where do I find the cow bell socket?

Thanks,

H.

My bus number (if any): RM1013

Reading through the threads, I wonder oif there is a common denominator.

Ingress of damp and increased friction caused by light seizure.

This is common in components and causes sluggish responses and poor torque performance on starter motors.
Often a combination of damp cold wear and tear and irregular actuation leads to odd noises and accentuates the worn parts.

The starter motor suffers the most from rare use as it seldom warms through enough to dry out the ingress of moisture from condensation caused by such a damp climate.

This was not a big problem when the vehicles were in daily use but anything laid up for several months were often problematic for weeks after reactivation.

A strip down, full clean and correct application of the right lubricants in the right places will sort the problem.

Hugo

Roy is referring to the battery booster socket adjacent to the isolator on refurbished buses. I assume yours was not refurbished and therefore you will not have one.

David

My bus number (if any): RML2276 M1001 T806

Correct. In that case, you'll have to check all the leads from the battery to the starter. good luck.