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BMC 1.5 wouldn't stop


Guest Cattleya

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I have a BMC 1.5 diesel on my boat (rebuilt recently at huge expense), I now have yet another problem with it, it won't turn off.

On the last couple of trips out it has run on for about 30 seconds after pulling the stop lever, but has stopped. Today I pulled the lever and the engine sped up instead of stopping. I have checked to make sure the lever on the fuel injection pump is moving fully across, and it does.

Does anyone know anything about diesel engines? What would cause this.

I managed to stop it by putting it into gear and pulling the lever, running in neutral and pulling the lever made the engine run slightly faster.

I did notice something has fallen off, what looks like a cap of some description with wire crimped to it. I'm really hoping it's nothing major as I have spent many thousands on the engine already.

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Hello Mate,have a look and see if the stop cable is any where near the throttle cable and isnt fouling it in some way, thats if it has a pull out stop button cable like my my bmc has

Andy

Thank you Andy, I don't think it's the cable as the actual lever on the fuel injection pump moves it's full travel. The first thing I thought was it was a cable issue, but unfortunately it isn't.

I'm hoping it will be covered by warranty if it turns out to be something major, I paid £3500 for a rebuild at the start of the year, which included a recon injection pump.

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Fuel cut off valve in the injection pump ?

I'm guessing that anything to do with the injection pump is going to be a case of getting the pump removed and sent for repair, which I'm guessing isn't going to be cheap.

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:wave hi there it sounds like the govenor which should have a metal tag and wire through it has lost the tag and the govenor has wound itself off so allowing excess fuel through making it difficult to stop if you ever need to stop a diesel in an emergency stuff the inlet manifold inlet with rags TAKING CARE NOT TO GET YOUR HAND OVER THE INLET AS YOU WILL HURT YOURSELF SEVERLY :norty:
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If the engine continues to run after the fuel cut off switch is activated it means that either the engine is continuing to receive fuel, which seems to be what most people are suggesting as the problem, or that the engine is finding an alternative source of fuel - if so, almost certainly engine oil. Needless to say, the second option is not good (a worst case scenario is that the engine will continue to run, increasing it's revs until it blows up or shakes itself to pieces). Have you (or somebody else) topped up the oil recently? Is it possible that you might have put a bit too much into the engine?

I'd suggest that since you seem to have checked for a really obvious, simple problem, it's probably time to ask the opinion of a qualified engineer (and check the warranty on your engine rebuild).

I know this is probably a bad time to ask, but when you decided to shell out £3,500 for a rebuild on an engine that's at least 26 years old (AFAIK, BMC 1.5s were built between 1968 and 1984), did you consider a modern replacement? If so, was there a reason other than cost why you went down the rebuild route?

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Diesel engine runaway is a rare condition affecting diesel engines, where the engine goes out of control, consuming its own lubrication oil and running at higher and higher RPM until it overspeeds to a point where it destroys itself either due to mechanical failure or engine seizure through lack of lubrication. For instance, a 1800 rpm engine can run to 4000 or 5000 rpm or beyond.[1]

Unlike a gasoline engine, which has a butterfly valve controlled by the throttle mechanism to control engine speed, a diesel engine's speed is controlled by varying the supply of fuel.

In many vehicles, a crankcase breather pipe feeds into the air intake to vent the crankcase; on a highly worn engine, gases can blow past the sides of the pistons and into the crankcase, then carry oil mist from the crankcase into the air intake via the breather. A diesel engine will run on this oil mist, since engine oil has the same energy content as diesel fuel, and so the engine revolutions increase as this extra "fuel" is taken in. As a result of increased revolutions, more oil mist is forced out of the crankcase and into the engine, and a vicious cycle is created. The engine reaches a point where it is generating enough oil mist from its own crankcase oil that shutting off the fuel supply will not stop it and it will run faster and faster until it is destroyed.

The unwanted oil can also come from failure of the oil seals in a turbocharged diesel engine, from overfilling the crankcase with oil, or certain other mechanical problems such as a broken internal fuel pipe. In vehicles or installations that use both diesel engines and bottled gas, a gas leak into the engine room could also provide fuel for a runaway, via the engine air intake[2].

The only way to stop a runaway diesel engine is to block off the air intake, either physically using a cover or plug, or alternatively by directing a CO2 fire extinguisher into the air intake to smother the engine.[3] Engines fitted with a decompressor can also be stopped by operating the decompressor, and in a vehicle with a manual transmission it is possible to stop the engine by engaging a high gear (ie 4th, 5th, 6th etc), with foot brake & parking brake fully applied, and letting out the clutch quickly to slow the engine RPM to a stop, without moving the vehicle.

http://en.wikipedia.org/wiki/Diesel_engine_runaway

scarey

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If the engine continues to run after the fuel cut off switch is activated it means that either the engine is continuing to receive fuel, which seems to be what most people are suggesting as the problem, or that the engine is finding an alternative source of fuel - if so, almost certainly engine oil. Needless to say, the second option is not good (a worst case scenario is that the engine will continue to run, increasing it's revs until it blows up or shakes itself to pieces). Have you (or somebody else) topped up the oil recently? Is it possible that you might have put a bit too much into the engine?

I'd suggest that since you seem to have checked for a really obvious, simple problem, it's probably time to ask the opinion of a qualified engineer (and check the warranty on your engine rebuild).

I know this is probably a bad time to ask, but when you decided to shell out £3,500 for a rebuild on an engine that's at least 26 years old (AFAIK, BMC 1.5s were built between 1968 and 1984), did you consider a modern replacement? If so, was there a reason other than cost why you went down the rebuild route?

I don't think it's an alternative source of fuel, and the speed only picked up slightly, probably from 500rpm to 700rpm and went back down as I pushed the stop lever back again.

Speaking to someone who knows a lot about these engines he said that the revs can pick up slightly when the engine is starved of fuel, it has been suggested I disconnect the stop cable and make sure the lever is going as far across as it can. That will rule out a cable problem.

Answering your second question, as to why I went with a full rebuild rather than a new engine, cost mostly. A new power unit would have cost around twice as much as the rebuild. I had everything rebuilt on my engine for £3.5k, inc a new cylinder head, new fuel injection pump, new heat exchanger, new water pump and everything else rebuilt. I might have gone for a new engine if not for the fact i had spent another £3000 the previous year on a new gearbox, prop shaft, prop, bearings, engine mounts, flywheel and various other bits and pieces.

The BMC 1.5 is a nice engine and parts are readily available, a Beta marine engine would have been nice, but would have required new wiring looms, controls, engine mounts and so on. The rebuilt engine dropped straight back in without any additional costs. Since my boat is worth about £10k to £12k, you have to stop spending at some point.

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Update to this, I run the engine for a good half hour yesterday in order to get it up to temp, then pulled the stop cable and it stopped instantly. I have no idea why it wouldn't stop last weekend, but it seems to be ok again now.,

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Sounds like it still ought to go back to the people who rebuilt it.

As for run away which this does not sound like I have had two , second hand, accounts of this. One was when I was an apprentice, a colleague test ran a standby generator powered a 1940 - 50 ish vintage Lister. This fine old engine ran at a terryfying speed and despite the noise my colleague attempted to stop it by suffocating it , it flattened the air filter ate the rag and kept on running. He them emptied a fire extinquisher into the air filter which calmed the beast. We were then issued instructions from the powers that be that in the event of a similar engine run away we were to to the same, ie run away and make no attempt to stop it.

The second case was about 8 years ago and involved a colleague with a virtually new Ford Ranger, the guy realising what had happened closed the door and watched from a safe distance. The theory was this was due to turbo failure and I was slightly concerned because I had just bought a Mazda car with what I believe was the same engine . It is however I believe a very rare occurrance

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I admit I know nothing about the installation of the BMC it is common practise for boat engines to have a solenoid valve that closes and interrupts the fuel supply when it is energised thereby stopping the engine.

I have problem with Kiki's which is on my winter 'to do' list.

We can tootle happily and moor and the engine stop button works perfectly, run hard and try to turn off and Mr Delmonte say no. In these cases I have to resort to a long 'stick' to poke in the engine and stop it :o

Check and see if you have a Solenoid Dave

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