<< Do all diesels have glow plugs? >>
Lots of diesel engines do not have glow plugs. Some rely solely on fuel-enrichment devices in the injection pump and many older designs had induction heaters where fuel is sprayed into the intake manifold through the coils of a heater element. This induction heater system was commonly made by CAV and was trademarked 'Thermostart'. However it seems almost universal these days for motor car diesel engines to have glow plugs.
My Rover 75 CDT (BMW engine) has glow plugs but it starts instantly without waiting for the light to go out. Some other DI diesels that I have driven seem to be the same but I feel sure that some engines do need the glow plugs to be hot before the engine will start.
It is possible that the high pressures generated in common-rail systems makes starting easier without glow plugs because the fuel is more finely atomised. The pressure difference between pump-line-nozzle (PLN) and common-rail systems is staggering, around 3,500 psi for PLN against 20,000 psi for common-rail in engines I have been involved with.
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www.beru.com/english/produkte/iss.php
Some interesting info on here, including the Instant Start System.
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Dizzy - some of the latest glow plug systems operate when the doors are unlocked and not when the key is turned. If the 75 has this it may explain why you don't have to wait for the light to go out before turning the key.
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In my experience most diesels will start sooner or later, even without glow-plugs. They are, after all, compression-ignition engines (at the risk of stating the obvious). Years ago I drove a Leyland Swift single-decker belonging to a voluntary organisation. It was ex-London Transport built without glow-plugs because it was always inside a garage when not in use. Post-sale it was kept outside, and it wasn't unusual to be cranking for 3-4 minutes before it would catch. Modern diesels have very efficient plugs - on my HDi the dash board light only remains on for less than a second, even in the coldest weather, and it always fires up first turn without necessarily waiting for it to go out. My BX diesel insists on 5-7 seconds light-on/light-out before it will fire, although can be persuaded to go if that time is reduced (or, in the case of my dear wife, ignored altogether).
CG
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I have a 2002 Polo 1.4TDI PD and although glow plugs are fitted I have never had to use them during the last two winters. Turn the key and it starts immediately.I understand you need to use the glow plugs only at extremely low tempratures.I think it has to do with the new PD deisel high pressure system.
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I don't know....but are trucks and other vehicles with large (always DI) engines equipped with glowplugs? I know they are not needed to enable a start, but out of interest?
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groups.msn.com/honestjohn/problems.msnw?Page=1 - Pictures say a thousand words.....
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Modern glow-plugs reach 1100 deg c in under 2 seconds, and the power to them is then regulated using pulse width modulation to stop them burning out.
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DL,
Most big diesels have some sort of manifold heating / enrichment device.
One engine everybody is familiar with, the old Transit 2.5DI has nothing. And if it doesn't start instantly in freezing weather - there's something wrong with it.
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As CG states, these are CI engines & rely on compression of cylinder gases to raise the combustion temperature.
Diesel fuel will self ignite at about 400 degrees C, so as long as the combustion chamber reaches this temp, the fuel will ignite as soon is it is injected.
I would guess high pressure injection systems that atomise the fuel better help the burning process.
IDI engines have a larger combustion surface area due to the pre-chambers & loose heat quickly, so need more assistance from the glow plug to reach the required temp. No doubt if you hung on the starter for long enough the heat from compression would eventually reach 400 C & the engine would start, albeit accompanied by a cloud of grey smoke.
I don't want to try to teach Granny to suck eggs but thought this might help some to understand the CI principle.
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I believe almost all large trucks have no cold starting assistance. They are all direct injection, and by and large, start instantly, too soon one would think given the large area for the oil to get around. However, also largely, properly maintained truck engines can get on for a million miles. Certainly, a million kilometers (620,000 miles) is not unusual at all on the cross-continental vehicles.
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The 10 hp Yanmar marine diesel I have just bought doesn't have any kind of pre-heating. It starts just like a petrol engine.
At the opposite extreme, a Perkins 4/99 in marine form had a heating element in the air intake. Fuel was dripped onto this, and the ignition set in a pre-heat position for 15 seconds until the element was smoking. The engine would then fire. It was needed only for cold starts.
If the engine was very cold or after standing all winter, a trick was to tie a rag onto a stick, soak it in diesel, set it alight and thrust it into the air intake while cranking the engine. There was a terrific 'whoomf' , a lot of smoke, and the engine invariably fired.
Very old semi-diesels were started with a blow-lamp.
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Interesting replies....thanks guys!
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groups.msn.com/honestjohn/problems.msnw?Page=1 - Pictures say a thousand words.....
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Cliff, I remember the 4.99 well - it was in production when I joined Perkins in 1959, later replaced by the 4.107 and then the 4.108. It was quite a small engine for a diesel (99 cubic inches or about 1.6 litre) and had a very low power output by today's standards, yet lots of cars and vans were fitted with it.
The air intake heater that you mentioned was the Thermostart that I referred to earlier and I think it was still in use in the early 1980s, perhaps even a bit later. It was a bit of a nuisance to find a place for it on the engine as it needed a fuel feed and reservoir as well as the heating coil. Perkins V8 engines had two heating coils, on in each manifold, and a WWII military V12 engine had three per bank!
Referring to Heebee's posting, the Perkins V8.640 that was introduced about 1965 was renowned in the truck industry for going 650,000 miles with nothing more than routine servicing. Part-way through its production it was found that a lot of cost could be taken out of it (like reducing rocker shaft diameter from 7/8" to 3/4") without affecting engine life. Later versions of this engine were amongst the first to have a cold-start fuel enrichment device in the pump instead of air intake heaters.
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This is probably irrelevant and confused but I can vaguely remember my father-in-law telling me about starting primitive diesel engines in the 1930's. He called them gas-oil engines and they had to have a small fire using oily rags lit under the sump to get them warm enough to start. Also a blow lamp could be used. I wonder whether these engines (make unknown) had electric starters? If not how on earth were they turned over on a starting handle!
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Bertj, these are the semi-diesels I was referring too. I saw an old Field Marshal tractor started up recently at a vintage rally.
The 'hot bulb' is heated up to red heat with a blowlamp, then a lever moved which decompresses the engine. The engine has an enormous flywheel, which with great effort can gradually be swung round and built up to a resonable speed. The the compression lever is moved back, and if lucky the thing starts. If not, back to the blowlamp and more exertion!
They work just like model aeroplane glow-motors I think.
Once started of course the combustion heat keeps the bulb hot.
It is fantastic to watch, and more particularly, listen to. At idling the whole tractor jumps slowly up and down in time with the cylinder explosions, and at speed - maybe 120 rpm? the engine can be heard half a mile away.
Other big engines were I think started using compressed air in a starter cylinder, or by means of a special smaller auxiliary engine.
I was also told recently that the BR Deltic diesels were started once at the depot using an enormous bank of batteries, and then kept running until the next service.
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Cliff, thanks for that - an absolutely fascinating topic; I'll do some looking round. Can't ask my father-in-law, he's long dead unfortunately.
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>>Bertj, these are the semi-diesels I was referring too. I saw an old Field Marshal tractor started up recently at a vintage rally.
Some versions on the field marshal you set light to a smouldering rolled up card which screwed into the top of the cylinder( it only had one running front to back of tractor-thats why at slow RPM the tractor rocked back and forth in time to piston which from memory was about 10 to 11 inches in diameter). you had to get a fair speed on the starting handle atached to a fly wheel some 6 inches thick and about 30 inches in diameter. this had a groove into which a wheel ran to give no compression until after about 6 turns it ran off the fly wheel with instant compresion. and just make sure you stand clear cos it could kick like a mule.but as you have said the sound was fantastic.
rustbucket
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I wonder whether these engines (make unknown) had electric starters? If not how on earth were they turned over on a starting handle!
I recently gave away a handbook for a 1930s Perkins Wolf diesel engine in which is shown how to start the engine with *two* men on the starting handle!
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Back in the 70's I worked for a while on concrete mixer trucks. In those days many of them had a diesel 'donkey' engine driving the drum. Most had electric starting but one had a jumbo sized starter motor that was 'wound up' using a starting handle. Inside the motor was a series of diaphragm springs, a bit like the spring on a modern clutch. As it was wound the springs compressed, when fully wound a lever was pulled, bendix thrown in, and the motor turned the engine over a couple of times. Didn't always work first time, and boy, was it hard work winding up for the third attempt.
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I forgot to mention that some, but by no means all, of the old diesels with starting handles had decompressors. With these, a lever was moved to open the valves slightly so as to lower the resistance to cranking. Once the engine was turning on the handle, the decompressor was released so as to let it fire up. Thank goodness we have progressed from those days!
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I saw a programme over the holidays with a diesel powered traction engine style road roller which took three men to start! One guy inserted a device similar to a lit cigarette directly in to the cylinder, the valves were lifted then the fly wheel handcranked by two men! An amazing bit of kit and easier than lighting a fire 3 hours before you needed to roll the new road.
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I left a company in June of this year to start with another,and upon leaving,my 2 year old Volvo FM12,had just over 400,000 kms on it.
I spoke to a friend of mine the other day,and asked him how it was going.He told me he had just been out in my \'old\' motor a few weeks ago and it was approaching the 500,000 km mark.
These motors are on a supermarket contract and while the majority of them do have the same day driver,the afternoon and night staff got what was available.In other words,they were going almost 24/7.
Some wagons will go onto a million kms,no problem,while others will go on past that,and despite the mileage,will still pull ok.It all depends on the number of \'careful\' drivers it has had in it\'s lifetime.
Average distance for a long haul motor can be up to 6-800 kms per day with only 1 driver.Thats 4000 kms per week on a 5 day cycle,or 210,000kms per year.However,if they are double shifted,as in the case of my old one,then you double the above.
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Interesting stuff Quinny!
That's a whole lotta miles.....
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Thinking about it, the Volvo, Dennis and Scania buses that I drive on a regular basis can be started from cold (at 0430) immediately as you would a petrol engined vehicle. Presumably, then, they don't have glow-plugs.
Cheers
Rob
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Hmmmm can't for the life of me remember where i read this - probably on this site to be honest - but i'm sure it has been said that VAG group PD TDI's claim to only need glowplug assistance below 2degC ambient temperature.
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I worked on a farm a few years ago and in spite of having DI engines, nearly all the tractors needed the use of various cold start devices to entice them into life in sub zero temperatures. An excess fuel button located on the fuel pump had to be depressed and then the key was held in the pre-heat position for 10 seconds or so. I believe this activated a system in the air intake which burnt diesel to heat the incoming air (as mentioned earlier in this thread). If both of these operations were carried out, the engine would fire up within a couple of seconds. If you tried to start it ignoring both of these, you would normally have to crank it for 30 seconds or so before it coughed into life with a lot of smoke! In slightly warmer temperatures (perhaps +2-3 degrees celcius), one of the tractors would fire up straightaway but would not idle without stalling for 5-6 seconds unless the throttle was kept open a bit. These tractors were early 1980s Fords. Later on in the mid '90s, the newer versions fired up straight away with no need for pre-heat, excess fuel etc. I wonder whether there was some form of automated excess fuel/pre heat?
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This thread illustrates perfectly one of the things I love about this forum.
A very simple basic question has brought forward all manner of interesting and related anecdotes, and taught me quite a few things I didn't know before.
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