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Runaway Engine Woes


Ocean30
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Suspicions confirmed I think!

A donkey engine was the engine on a nodding donkey oil well extraction pump.  Then the engine on the back of a commercial trailer for driving hydraulics or refrigeration. Common on early in transit concrete mixers.

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4 hours ago, bizzard said:

A main engine wouldn't be called a Donkey, just the aux.,

Correct, my main engine will be a 48v 10hp electric go cart motor driven off a 5kW air cooled gen set in the survivors cabin charging 4 dedicated 12v NiCad batteries, with a pulley on the main prop shaft. Alas I can't install that motor until the donkey that will only be used in emergencies is installed.

 

Oddly enough Wiki say that a Donkey engine was originally an old steam engine used to replace a team of donkeys walking around in a circle I presume.

  Most sailors or fisherpersons tend to use the term for an old diesel, although the BMC is only around 60.

Edited by TNLI
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  • 3 weeks later...

So, finally got round to removing pump today. Took me around an hour thanks to good access and compliant bolts! There was significant play, forwards and backwards of the shaft. Is that normal? 
Refurb pump ordered.I can see where the oil and diesel would mix at the oil port located at the front of the pump. So hopefully the new pump will arrive soon and go on equally as easy as it came off. One last thing. The score line on the timing for the new pump should be applicable to my pointer on the housing. I assume the refurbished pumps come with this score line?  

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2 minutes ago, Ocean30 said:

The score line on the timing for the new pump should be applicable to my pointer on the housing. I assume the refurbished pumps come with this score line?  

 

Yes, it should come with the score line but whether it will or not is open to question. Don't alter the pointer unless you use the timing gauge.

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58 minutes ago, Ocean30 said:

So, finally got round to removing pump today. Took me around an hour thanks to good access and compliant bolts! There was significant play, forwards and backwards of the shaft. Is that normal? 
Refurb pump ordered.I can see where the oil and diesel would mix at the oil port located at the front of the pump. So hopefully the new pump will arrive soon and go on equally as easy as it came off. One last thing. The score line on the timing for the new pump should be applicable to my pointer on the housing. I assume the refurbished pumps come with this score line?  

If you can, compare old and new score line before fitting!  Remember to clean out all crankcase breathers especially the side one and any pipes to the air filter.

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Excited to receive a new pump for the 1.8 bmc. Although the pump numbers are slightly different. One is mid 4900 and the other a 5000. Will this work with the current engine? One also has a nut at the back where as the new one doesn’t. 

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1AC220E2-37F9-495C-954F-B24F113BE813.jpeg

Edited by Ocean30
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32 minutes ago, Ocean30 said:

I’m guessing the nut was where the solonnoid electric shut off would have gone so shouldn’t be an issue? 

I agree, it was fitted to 1.8s in vehicles.

 

I am sure it will work just fine but may have a different maximum fuel volume set. That, in theory will give you a higher or lower maximum speed, I would guess higher, but you would be ill advised to use that for long. That is even if the prop  allows it and does not hold the revs down.

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So Calcutt marine confirmed this and thanks Tony. The chap Roger certainly knows his pumps 🤯. I’ve read other  threads about timing these. It of course has a scribed line on the pump and the pointer is in place. The line is pretty much the same as the one that came off. Fitting the pump is easy as it has a master spline so that’s helpful. So fingers crossed to getting it fitted up tomorrow and running smoothly. Although nothing ever goes that well and I’m sure the pump will need some jiggling around before she runs up 🤞 

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44 minutes ago, Ocean30 said:

Although nothing ever goes that well and I’m sure the pump will need some jiggling around before she runs up

 

Unless the score line is badly wrong the timing chain/tensioner is very badly worn it should be fit, bleed (low & high pressure), fire up. If it won't fire up it is more likely to be insufficient low pressure bleeding. Once you think you have all the air out fo the low pressure bleed points keep going for another 30 seconds or so.

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An interesting day tinkering. Fitted pump, not much of an issue at all. Bled and fired up with no smoke. I lined up the timing pump to pointer so all good. However, I put her into gear whilst tied up and she would only hit 1300 revs. I was wondering if the timing needs to be slightly advanced? She hit over 2400 before on a burst. Would maintain temperature at 2000 revs when punching the tide on Breydon water. I’m going to river test her tomorrow. Any thoughts if this is where I could be losing power? 

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8 minutes ago, Ocean30 said:

An interesting day tinkering. Fitted pump, not much of an issue at all. Bled and fired up with no smoke. I lined up the timing pump to pointer so all good. However, I put her into gear whilst tied up and she would only hit 1300 revs. I was wondering if the timing needs to be slightly advanced? She hit over 2400 before on a burst. Would maintain temperature at 2000 revs when punching the tide on Breydon water. I’m going to river test her tomorrow. Any thoughts if this is where I could be losing power? 

 

Yes, first ensure the throttle lever on the pump is in the same position when moved fully one way is the same as on the old pump. Then  the idle damper may be restricting the governor valve movement. The manual gives instructions for adjusting. Take care with the damper, it is all too easy to rip the female thread out of the top of the pump.

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Thanks Tony…..So slacken off the 3 nuts and slightly rotate the pump. Setting the cables was a pain in the arse! She is ticking over at at around 500 rpm without issue. The cable pulls the lobe around to the stop. That pin is secured with wire so I assume not to touch it! So both idle and full revs going to the right points.  If I do advance do I twist the pump towards the block or away? Cheers Tony! 

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1 hour ago, Ocean30 said:

Thanks Tony…..So slacken off the 3 nuts and slightly rotate the pump. Setting the cables was a pain in the arse! She is ticking over at at around 500 rpm without issue. The cable pulls the lobe around to the stop. That pin is secured with wire so I assume not to touch it! So both idle and full revs going to the right points.  If I do advance do I twist the pump towards the block or away? Cheers Tony! 

 

NO, that adjusts the timing and on a bought in pump properly fitted that is a less likely fault.

 

1. The throttle lever on the pump is normally adjustable to maybe 20 different positions and the person who built the pump does not know how your boat is set up. So if it was fitted in a different position on the new pump you could easily lose throttle movement. So take the cable off and push the lever fully one way. Do the same on the old pump and ensure both levers are in the same position. Adjust the new one to match if required.

 

2. The idle damper is right on the top of the pump between the two levers. There is a bolt with a bleed screw in the head and a lock nut. If the pump rebuilder did not adjust it properly then it can easily stop the governor valve rising to the higher speed/load positions. You need to read up how to adjust it in the manual.

 

Once you have ensured both those are OK then just maybe the throttle stop is in the wrong position but normally the maximum speed stop is up inside a tamper proof tube secured with wire and a lead seal. You really should not adjust that to give more speed because that way lies a blown up engine. However if the maximum speed in NEUTRAL is less than (say) 3500 to 4000 rpm then you  could adjust that stop to give more speed. The maximum speed was given as 4400 but there is no way that I would adjust a small BMC to that speed.

 

You must check the idle damper first.

 

 

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20 minutes ago, Ocean30 said:

Are you referring to this bolt Tony? 

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NO, that is a bleed screw. Do you not have a manual? If not do a web search and download the one on the Norfolk Broads Forum. Unless you have an old design of pump the item I am talking about is between the throttle and stop lever spindles right on top of the pump.

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Hi Tony. So I went and had another tinker. Pump definitely goes round to both stops so using full range of throttle. Nothing more than 1200 rpm. Tony I found the bolt you were on about. The one below is the setting on the old pump. The bolt on new one is screwed right in. I’m assuming this is governing the amount of fuel so unscrew to allow more fuel through? Is it as simple as that? No special tools etc! 
cheers Simon 

E31C4E98-7989-4D2A-A3A3-E68C411E2219.jpeg

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44 minutes ago, Ocean30 said:

Hi Tony. So I went and had another tinker. Pump definitely goes round to both stops so using full range of throttle. Nothing more than 1200 rpm. Tony I found the bolt you were on about. The one below is the setting on the old pump. The bolt on new one is screwed right in. I’m assuming this is governing the amount of fuel so unscrew to allow more fuel through? Is it as simple as that? No special tools etc! 
cheers Simon 

 

 

Yes that is the idle damper and if it is screwed right in it will limit the maximum fuel delivery and thus speed.  The little 8mm hexagon on top is a bleed screw. You are interested in the roughly 11mm hexagon screw and lock nut.

 

There is an adjustment sequence so you need the manual, either download it from the Norfolk Brads Forum or here http://www.boatservicehaarlem.nl/bmc_tempest.pdf

 

The screw is NOT the governor, it is the idle damper that helps prevent the engine stalling when slowed to idle fast and under load. If you mess the adjustment up it will either do what it is doing now to a greater or lesser extent of stall. Please download a manual and follow the instructions so you get it right and are not guessing.

 

 

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Can’t really mess it up. The worst that could happen is that I have to screw it back in? famous last words….. I’ll have a tinker tomorrow. I couldn’t see anything in the manual that referenced that particular part and it’s setting. It’s running ok. No smoke when warm. Just lacking that power. Cheers for your advice. 

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I thought it was in the actual BMC manual but there you go. Found this ref. a Perkins that uses the same pump:

 

The Perkins instructions, which the pump is a CAV may help, but no promises !

Slacken Locknut to enable anti-stall body to be unscrewed to mid point.
Adjust idle speed to about 625 - 650 RPM
Screw down anti-stall body until slight increase in enginer speed, bring back half a turn and lock with locknut.
Open throttle with NO load to max, bring back to idle. If return to idle takes more than 2 - 3 secs then body has been screwed in too far. If engine stalls or near stalls body hasn't been screwed in enough.
Repeat until happy medium achieved.

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So…..turns out the idle governor was set right. Took her out for a trial run. 
at 900 Rpm it would push her up to 5mph punching the tide. 1200 RPM would give me well over 6mph. Oil pressure sat at 45psi. Temperature was good. Did have a moment of horror when I saw the crank case pressure had hit over 80 psi….lead had come of sensor!


so it’s hitting the speeds at lower revs. Did cut out when I tried to reverse at speed but that was just the idle been set a bit low. She is a 30 foot boat. 

she is a bit Smokey on idle although nothing terrible as the revs build. I was thinking about getting the injectors re furbished. Also take a look at the air filter as this may be problem? 
 

I did wonder if my prop had become fouled? Before I had run away I had rescued a boat and had gone into shallow water. I think it’s unlikely though. 
 

Is it worth getting the injectors refurbished? Anyone had experience of this? Be good to hear. Or is it just a common problem that old diesels are just smoke a bit! 

 

Cheers. 

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