Engine start problem

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single

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1.5 Thornycroft diesel, new engine battery.
It usually starts from cold as normal but if i turn it off and leave it for a few hours it doesn't want to start.When it eventually does, there is a big cloud of white smoke. Any ideas where to start looking? The battery is fine.
 
single said:
1.5 Thornycroft diesel, new engine battery.
It usually starts from cold as normal but if i turn it off and leave it for a few hours it doesn't want to start.When it eventually does, there is a big cloud of white smoke. Any ideas where to start looking? The battery is fine.
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White smoke could be moisture in the cylinders. Are you loosing any coolant? If so you might have lost the cylinder head gasket. The fact that it runs at all would suggest its not a catastrophic failure though, not yet anyway. A compression test should let you know.

**When you say it usually starts, do you mean that it only refuses to start if it has been running recently? You only need fuel, air and compression for a diesel to run so if it won't run it must be missing one of the three. If by white smoke you actually mean grey smoke then that would point more towards the fueling. Being anything from air in the line to incorrect timing.
 
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Back pressure built up in the return line will create vapour lock, it happens when the engine is hot. Therefore In my opinion you have a block in the return line. Also check the flow to the engine, you need adequate flow through to avoid getting vapour block when engine stops.
 
BMC 1500 heater plugs need to have the orifices reamed out on a regular basis to remove carbon build up that blocks the air space
 
In addition to the suggestions above and my own experience with the BMC 1.5, I would add the following.

White smoke during start up can be due to the following causes:

(a) Burnt out glow plugs......................You say that the engine starts ok when cold so that would tend to rule out the glow plugs as from my experience with a 1.5 in a previous boat, they do need the glow plugs to get them started

(b) Incorrect injection timing…...……….….If it starts from cold then timing should be ok

(c) Compression problems …………..........If it were poor compression then this would have an impact on cold starting

(d) Blown Head Gasket…………...............This could be a possibility but you would see a drop in the freshwater coolant level

(e) Poorly sealed piston rings…………….....Not experienced this but this would also have an impact on cold start

(f) Leaky valves …………………................ As (e) above

(g) Cracked Head………….......................If this was the cause, then you would see similar problems with coolant level

(h) Cracked Block................................As (g) above

(i) Injector is stuck or not working…….… Stuck injector or dribbling injector is usually accompanied by very loud diesel knock as the engine fires the dribbled fuel before the correct injection timed point.

The problem is to try and work out if the white smoke is unburnt fuel or steam, one suggestion I have is to run the engine and then let it cool down.

Now before you start it, keep the engine stop pulled out so that you do not inject any fuel. Get someone to press the starter and look at the exhaust and see if there is any signs of steam, if there is, you may have your answer. The steam being produced as any water in the cylinder space is vaporised by the heat of compression and the glow plugs.
 
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The boat I have bought has a BMC diesel which was misbehaving when I bought it, I was going to have it ripped out and buy a new engine but I remembered that when in the early 1970's there was a fleet I bought cars from and I had to also buy the vans, which were Austin J4 Diesel Vans which had these BMC diesel engines in, and they were hammered perhaps 2 or 3 hundred thousand miles. However on reflection from this firm alone I must have bought over 50 of these vans and I never had to have any engine work done, they were so reliable, which is why I persevered with the engine in my present boat, and I am glad that I did as the engine is running fine, now.

You should try a Cylinder Balance Test, get the engine running, set the engine to 1000 revs and slacken off a injector and the revs will drop, do each one and all the revs should drop by the same amount, if one cylinder dosent drop as much as the others that is a cylinder where the problem is.

If Diesel Compression Testers were not so expensive I would have one, so to diagnose what was wrong with my engine I had a mobile mechanic do a compression test which cost me £40, fortunately all my compressions were all high and virtually identical, so then I took the injectors to a diesel specialist for a service and bought new glow plugs, and when installed then started to try and find out why the engine would not run for more than 10 minutes, which is another story.

These BMC engines are worth persevering with, over engineered to todays standards, ok getting a bit scarce but still in use in thousands of boats thought the country.
 
Answer is it is not a BMC, Thorneycroft used the BMC 1.5 for years until production of the engines was stopped (some still made in India) Thorneycroft then used the Mitsubishi as the base engine. Totally different unit but most of the comments still apply.
 
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