Does a high compression diesel engine need glow plugs be used to start

[Industrial Toys]

I may not know my Diesels, but I know a wore out one is miserable.

I looked up direct and indirect injection diesels on Wikapedia and find it hard to believe that there are no such headings, but related material.

So where is this secondary (pre) combustion chamber? How big a passage to the cylinder? How is exhaust gas scavenged from this chamber?

Thanks.

 

[bigdeano]

The pre-combustion chamber in an indirect injection engine is small and sucks the heat out of the compressed air, thus a glow plug and higher compression is needed. With direct injection the air stays hot enough without the glow plug.

My Isuzu 4FB1 engine requires the glow plugs if engine temp is below 140 if I remember correctly.

 

[adventure bob]

Glow plugs are not spark plugs. Every cycle of the diesel does NOT fire a glow plug. Diesels, when running, need NO extra heat to run. Thus the term "compression combustion engine."

 

[adventure bob]

Glow plugs are not spark plugs. Every cycle of the diesel does NOT fire a glow plug. Diesels, when running, need NO extra heat to run. Thus the term "compression combustion engine."
"Air is compressed until it is heated above the autoignition temperature of diesel. Then the fuel is injected as a high pressure spray. There is no ignition source. As a result, diesel is required to have a high flash point and a low autoignition temperature." The Physics Factbook

"Diesel engines, unlike petrol engines which rely on a spark to ignite the air-fuel mixture, function due to the auto-ignition of diesel fuel when subjected to high pressures. Under high pressure, the temperature of the diesel fuel increases to a point where the fuel self-combusts. In cold weather however, this temperature is not always achieved and glow plugs assist by heating the air-fuel mixture to assist in cold starting." From NGKs Website.

 

[Egon]

I may not know my Diesels, but I know a wore out one is miserable.

I looked up direct and indirect injection diesels on Wikapedia and find it hard to believe that there are no such headings, but related material.

So where is this secondary (pre) combustion chamber? How big a passage to the cylinder? How is exhaust gas scavenged from this chamber?

Thanks.

Read post sixteen.

 

[Egon]

Something else that enters into this is, the design of the "injection pump".

Old pumps worked at lower pressure and sprayed in nearly "droplets" of fuel. Newer higher pressure pumps, spray the fuel in at nearly a fog of fuel and that's a lot easier to ignite.

Bottom line is, (as was already said) where you spray the fuel makes the difference! (direct or indirect injection)

Thank the stupid EPA for those dam glow plugs, and everything you have to have because of them!

SR

There were glow plugs in indirect injection diesels before EPA.

Some common rail direct injection now use electronically controlled injectors with multiple nozzles for the injection.

 

[Industrial Toys]

Thanks. That link in post 16 showed me what I wanted to see. So the glow plug in a indirect injection motor is presumably in the pre-injection chamber. And, can one have a heater element in the intake manifold in both styles of engines?

 

[buickanddeere]

Cranking speed is a factor . Drag from a hydraulic pump usually can not be helped unless there is some manner of "destroker".
Any machine with a manual transmission will crank faster if the clutch is pushed to the floor.
Not unusual to see a tractor while being cranked wasting power raising a leaked down three point hitch.
Sometimes it's just a matter of enough voltage and current to a starter that is in good condition . Often somebody will cheap out on one battery instead of two. Cheapo Walmart light weight battery cables . Connections to chassis are often suspect , best solution is to run a new HD ground cable to a starter bolt . Generic starters are not that expensive, sometimes a size or two larger is a simple bolt on.
Start off by measuring the voltage between the starter's main stud and the starters cast body. I'll bet you a beer it's way under 10-1/2 volts.

 

[sd455dan]

Thanks. That link in post 16 showed me what I wanted to see. So the glow plug in a indirect injection motor is presumably in the pre-injection chamber. And, can one have a heater element in the intake manifold in both styles of engines?

LD1 spelled it out well,
for your engine inspection
check out the Blow by out of a crankcase breather-
That will be the give away that the engine is well worn and will be harder to start especially on cold days. If you are still considering purchase a compression test could be done through the glow plug holes.,

If glow plugs are needed that much on a warm day How well (if at all) will it start on a cold day...




ps. counter point as stated earlier- believe that some indirect injected diesels are set up to use the glow plugs at fairly high ambient temps.

Just need to know if the tractors engine you are dealing with is one of them, and just how worn that engine is.

 

[art]

Over the years we have worked with glow plugs, intake heaters and some other rare stuff. Yes some engines still seem to need a heater of some sort and some need more of it then others! We have found that low end rebuilds use too thick of a head gasket often after-market and with the reduction of compression the starting is definitely hindered..