GBW

No, it is clear of the rocker cover. Rusty interior is visible through the hole. There is no machined surface and it is connected to the waterways. This engine is probably as old as I am (do the search!). 5/8" UNF is 18 tpi. this corresponds to a pitch of 1.41mm. For some strange reason, my elderly thread gauge, made in the USA!, does not present 18 tpi. It does offer 1.5mm, but that doesn't quite fit. The plug is short which doesn't help. (I am not going to fire up my 0.00001 measuring microscope1!) 5/8" diameter is 15.875mm. I think I am going to go with 5/8" UNF.

Why? I don't think metric was very common when this engine was built! However, the plug gauge I used which was a very nice fit in the hole, happened to be M16 fine! It had been returned to the wrong drawer.

Thanks. What's it for then? I could use it for an additional water temperature sensor I suppose.

The threaded hole next to the blanking plug (5/8" UNF). It seems to connect to the waterways. Is it usable for calorifier take off (in or out)? The hole next to the blanking plug (tapped 5/8" UNF).Is it usable for calorifier take off (out or return)?

I've found the definitive values in a BMC repair manual. Top ring 0.012-0.017 Remainder0.008-0.013.

Try before you buy. Some can be uncomfortable round the neck after a while.

Brilliant Tony - thanks. Now to find a Torx socket!

The stop solenoid usually has insufficient pull to close the stop valve. The valve return spring has insufficient push to open it. It would seem the valve is sticky. I have been unable to discover how the shaft is held in the injection pump. Can anyone advise please?

I have the same interest and found this post by accident. My reason us that I have a fear of engaging the starter motor while the engine is running. To preempt the incredulity, I have two identical buttons adjacent to each other, one for start, the other for stop. I have a remote "start down", "stop up" toggle switch at the helm. I also have a wife who can't remember which switch to push or toggle. If she pushes "start" when she meant "stop", there will be a horrible noise and the chance of damage. I am happy with the arrangement, as, in the engine bay, I can select which button by touch and at the helm, "Up" means stop and "down" means start. All perfectly logical BUT .............! If I can detect the engine is running, I can disable the circuit to the start solenoid. The oil pressure switch doesn't do it as the starter would cease once the oil pressure rises. Likewise, the alternator would not serve for the same reason. Even a pulse detector on the crankshaft would present the same problem. However, as is often the case, describing the problem to others inspires a solution. A delay in the detection signal produced from any of the above, should solve the problem. Thanks for the invitation for self reasoning!🙂

Today I met someone who used to work for Lotus. I explained my experience. He asked "Was it a bakelite cap on the solenoid?". He agreed that crazing of the surface had probably caused electrical tracking through the cap sufficient to ignite the adjacent cables.

Thanks Tony.

My replacement 1.5 diesel engine is ready for its pistons. I can't find any recommendations for ring gap setting. Anyone help please?

Noting Tony's observation on the location of the solenoid, I fitted the spare replacement as it was a "topside" solenoid. Incidentally, it should be possible to remove the solenoid whilst in-situ which is not the case with the "downside" one. The replaced starter started the engine without problems and I eventually made it back to Cardiff on three tides. The problem of accessibility to the nuts nestling against the casting could be solved by introducing a bush under the nut head (or even a snack of washers. The cause of the fire remains unknown. The disintegrated solenoid showed no signs of the contacts being welded; indeed, as explained earlier, the battery lead contact remained connected to the lead. Many thanks for all the advice and especially to Tenby Harbour Master who spent a couple of frustrating hours failing to remove the same nut that defeated me. The thought of the solenoid operating with the engine running is horrifying. Is it possible the starter would disintegrate probably running faster once the engine speeded up. Goodbye starter ring?

There were three bolts but not what I would have fitted. One top one was easy, the bottom one was accessible with a long extension on a socket and undid surprisingly easily (after numerous attempts and trips in the bilge (water). However, the third top one was easy of access but impossible to apply any sort of spanner due to the proximity of the casting. The nut was eventually removed after drilling it’ll split it. I think socket head screws will be a better replacement. I will test the starter on the “bench” before replacing it.

The mystery deepens. Returned to the boat. As expected, there is only one connection to the solenoid - the battery. The cable is securely attached to the solenoid stud. However, the stud is not attached to the solenoid. This is probably the result of the fire. The end cap is brittle and partly disintegrated. There is no obvious sign of a shorting mechanism. Is it possible the cap may have become carbonised and progressively increasingly conductive permitting a short to frame. It took around five hours to remove the starter due to bad choice of bolts.

You're right! The current is what generates the magnetism that moves the needle and the voltage generates the current. Lets leave it there! Overnight, I had the thought that the alternator output is actually connected to the battery not via the solenoid terminal but via another route. If that is the case, my initial diagnosis is wrong and I am now worried that the cause is more serious. I return to the boat today and will report back.

No - sorry, They are micro ammeters. But seriously, is there any difference? I believe a "voltmeter" measures the current through a resistor which is sized to give the correct deflection for the voltage applied. (I used to build multimeters!)

I think that is what I just posted! "My intention is to measure the volts from across the existing cables with micro-ammeters. " My digital ammeters are by Nasa but live below. It is a sailing boat (sorry!).

Repeating an ammeter in the cockpit (times 2 as I have two alternators) implies heavy cables with quite long runs. My intention is to measure the volts from across the existing cables with micro-ammeters. I have done this to sense the glow plug current and it is a boon. Fsd means four glow plugs drawing current, half full scale, two etc. The problem is finding meters with moving coil mechanisms as they all seem to be thermal (at least the ones I have found - it isn't obvious until you use them). However, I have found some cheap (i.e.Chinese!) meters on ebay fsd 50 microamps which will do the trick. Needs calibrating of course. The same meters will do for volts as well. I am a firm believe in monitoring - information aids diagnosis! The thermostats I referred to are as these;- https://www.ebay.co.uk/itm/254292043897 All these things take time!

The ammeter is below (and the cockpit mounted repeater not yet fitted) but all that would show, I think, would be intermittent charging with a flickering needle (which I would probably ignore!). I have a bunch of clip on thermostats, penny sized, intended for coolant temperature monitoring but one adjacent to the starter may well have been effective.

The shroud I referred to is internal - black in the photo. Using a bit more courage, the body did pull off. The tag connections to the coil will need unsoldering I think to allow removal of the cap. However, with a bit of luck and using the invaluable advice from you and MtB, I might get away with swapping just the body. There is no reason to think the motor has been damaged. This seems to be the cap;- https://www.ebay.co.uk/itm/183653472588?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20220705100511%26meid%3D53ad4aa2c3cc47f39555afaaccf1a579%26pid%3D101524%26rk%3D1%26rkt%3D1%26itm%3D183653472588%26pmt%3D1%26noa%3D1%26pg%3D2380057%26algv%3DRecentlyViewedItemsV2&_trksid=p2380057.c101524.m146925&_trkparms=pageci%3A1333ea0d-084c-11ee-b214-a2477a6c0310|parentrq%3Aaa3d6e431880ab8f2efb20ddfffd74df|iid%3A1 Thanks to both of you.

Access on sea-going boats varies. I sailed with someone on his 47 foot ketch and become convinced that just after the keel was laid, the bed were installed, the engine mounted on them and then the hull was completed around it! Access was virtually nil and the engine needed to be lifted for repair. On the other hand, some boats have engine spaces all around them. Mine lies in between but, inevitably, the oil filter and starter motor are down the "wrong" side! Fire on boats in general is very rare but when the engine is "below", evidence takes longer to reach the helmsman. When we arrived at Tenby dock, two fire officers were waiting. They performed a pyrotechnic inspection of the engine space using a hand held device. Perhaps such a device exists for a permanently mounted operation. Temperature sensors are generally fitted but normally on the cooling system. I would never (previously) have considered one at the starter motor. I may change my view! In the many cars I have possessed I can't ever remember checking the connection to the starter motor. Incidentally, that was the second "loose nut" experience on the trip. The first involved a through bulkhead connection where 5 volts were lost from the (different) alternator to the batteries due to a loose nut. It is now a loctite nut. The spare starter I have is in working order and I am reluctant to wreck its usefulness by an unsuccessful dismantling. The access to the solenoid on the boat is relatively simple. Two of the three bolts securing the starter are visible and accessible. The third is below and difficult, although I seem to remember in the dim and distant removing and replacing it for some reason. Visible in the photo is an internal rubber shroud. extraction of the operating armature is now reluctant. Perhaps I'll try pulling the motor armature next. Would removing the operating pivot pin be helpful?

A warning to all! I am cheating a little as my boat only spent a year on a canal (The Gloucester-Sharpness) and is now sea borne but this forum is invaluable for information on my BMC 1.5 engine. A salutary warning. Sailing from Milford Haven to Worms Head under power (no wind) to await the tide, when 8 miles off I went below to update the log. Checking the engine for water temperature and oil pressure I was greeted by flames. These were extensive but succumbed to CO2 and water. Although yet to be confirmed, the cause seemed to have been the alternator output connection to the starter solenoid. This, as in cars, is a direct connection perhaps for convenience. I was unable to stop the engine with the stop solenoid (an unrelated fault referenced previously) but the CO2 finally did so. I could not subsequently restart. My suspicion is that a loose connection at this point caused resistive heat eventually sufficient to ignite adjacent flammable cables and hoses. The solenoid is wrecked but the motor may be ok. My on board manual tells me that the two cannot be separated. Back home, looking at my spare, I believe this to be incorrect. Time will tell! I return to the boat tomorrow (in Tenby after a tow from the lifeboat) and will update. What do others do to detect fire? There was surprisingly little smoke.

There is no matching slot on the gasket. The oil feed is through the circular boss. The slot appears to be redundant.

And the slot?