Heating Before Engine Start

[Nishan.dj]

Hi friends,

Can anyone explain why is it required to heat the engine before start in 4DR5 Jeeps? It may required in some other vehicles as well. The vehicle can be started even without heating but it is recommended to heat. So what does it happen if the vehicle is started without heating. Mine, it takes 18-30 seconds to light up the heating indicator just above the key in the dash board & I think its the average time it takes. Please post anything you know. Thanks in advance.

Regards,

Nishan

(just found this on yahoo answers.)

Edited October 10, 2011 by Nishan.dj

[Elvis_Pil]

Not an expert on diesel engines in anyway.. but older diesel motors tend to use glowplugs as opposed to spark pulgs you see in petrol motors. The glowplugs function on electrial resistance which is then used to heat them upto the optimal teperature needed to fire up engine. This process takes a few seconds which is why you need to wait a while when starting the engine when its cold.

Someone correct me if I'm wrong

Edited October 10, 2011 by Elvis_Pil

[Ripper]

Not an expert on diesel engines in anyway.. but older diesel motors tend to use glowplugs as opposed to spark pulgs you see in petrol motors. The glowplugs function on electrial resistance which is then used to heat them upto the optimal teperature needed to fire up engine. This process takes a few seconds which is why you need to wait a while when starting the engine when its cold.

Someone correct me if I'm wrong

dont think it's accurate to compare glow plugs on diesels to spark plugs on petrols.

Glow plugs only help in the ignition process but don't really ignite the fuel like a sparkplug does

18-30 seconds is too long imo. mine heats up in about 3-4 seconds, slightly more in colder climates.

either your battery is weak of glowplugs are going bad.

on diesels... combustion happens when compressed air in chamber meets pressurized diesel fuel. diesel is sprayed via high pressure injectors and it's the pressure that causes the fuel air mix to heat up and explode and burn the fuel giving power.

glowplugs help to get the cumbustion chamber temp up to help in this process. A colder air mix wont be as helpful as a hot air mix for obvious reasons

[Nishan.dj]

dont think it's accurate to compare glow plugs on diesels to spark plugs on petrols.

Glow plugs only help in the ignition process but don't really ignite the fuel like a sparkplug does

18-30 seconds is too long imo. mine heats up in about 3-4 seconds, slightly more in colder climates.

either your battery is weak of glowplugs are going bad.

on diesels... combustion happens when compressed air in chamber meets pressurized diesel fuel. diesel is sprayed via high pressure injectors and it's the pressure that causes the fuel air mix to heat up and explode and burn the fuel giving power.

glowplugs help to get the cumbustion chamber temp up to help in this process. A colder air mix wont be as helpful as a hot air mix for obvious reasons

Thanks Ripper,

I think it is the problem with glowplugs because I replaced the batteries recently. So how do we check the glowplugs to make sure its time to replace them? Thanks.

[xlr8r]

It may not be the glow plug nor the battery... it could be a fixed timer taking too long to get it self offed... Most timers in the market are not like the original factory fitted which is connected to the thermostat of the engine to chk if its warm or not.

Check if the glow light stays on for 18 or so secs even if the engine is hot.. If that's the case replace the timer with a original before u do any other replacement.

[The Don]

The best explanation I found.

http://www.ehow.com/list_6461234_functions-glow-plugs_.html

[Sylvi]

Hi friends,

Can anyone explain why is it required to heat the engine before start in 4DR5 Jeeps? It may required in some other vehicles as well. The vehicle can be started even without heating but it is recommended to heat. So what does it happen if the vehicle is started without heating. Mine, it takes 18-30 seconds to light up the heating indicator just above the key in the dash board & I think its the average time it takes. Please post anything you know. Thanks in advance.

Regards,

Nishan

(just found this on yahoo answers.)

'Nishan.dj,

When I read posts above I find there were few answers for your post.Basically what heater plugs do is to heat up the intake air to your engine cylinders during on a cold start after few hours of engine is not working, so that heated air will make the combustion instantaneously.

I will give my experience about heater plugs. Some engines have only one heater plug fixed to inlet manifold that is manufactured to battery voltage or little lower then that enable to driver to see the glow heater on the dash board panel to see that the heater indicator wire coil till get red hot before you apply the starter motor to start engine.

Some are 1.5 volts to 2 volts heater plugs, they are wired in series to your electrical wiring system with a glow indicator on your dash board panel.Then there are electronically controlled heater plugs in newer vehicles only with a indicator bulb on the dash board.

They go off to the programed time, when the engine get under compression, some drivers on and off the heater position of the IGN switch, so that glow plugs will be heated for longer time before they operate the self starter motor of the IGN switch. I have experience of that way and advised number of diesel newer automobile users to do that in the morning for electronic timer fixed engines. This above method was a temporary thing till they go for a engine overhaul.

You can still start your engine without the heater but it will take longer time and your self starter motor will have to work long working time depending on your engine condition.

If your engine is low compression then you cannot start even after heating then you will have to start with a push start.

If you want any more explanation on the above please do post till you get satisfactory answer to your question.Can give you more advice on the difficult cold start of your engine.

Sylvi Wijesinghe.

[harshansenadhir]

It may not be the glow plug nor the battery... it could be a fixed timer taking too long to get it self offed... Most timers in the market are not like the original factory fitted which is connected to the thermostat of the engine to chk if its warm or not.

Check if the glow light stays on for 18 or so secs even if the engine is hot.. If that's the case replace the timer with a original before u do any other replacement.

This is not valid for J44 where pre-heating is manually done by turning the ignition key anti clock wise.

OPs pre heating system must have modified with a timer relay. As ripper said get the plugs tested by taking them off or through a multi meter. Be careful when taking them off as the plugs in 4DR5 engine tend to break apart and fall into intake manifold.

[Sylvi]

This is not valid for J44 where pre-heating is manually done by turning the ignition key anti clock wise.

OPs pre heating system must have modified with a timer relay. As ripper said get the plugs tested by taking them off or through a multi meter. Be careful when taking them off as the plugs in 4DR5 engine tend to break apart and fall into intake manifold.

'harshansenadhir',

You are correct as stated on your post.

I remove the heater plugs test them separately by connecting to a battery to see them working properly, multimeter will give only a reading of continuity.

Sylvi Wijesinghe.

[Nishan.dj]

'Nishan.dj,

When I read posts above I find there were few answers for your post.Basically what heater plugs do is to heat up the intake air to your engine cylinders during on a cold start after few hours of engine is not working, so that heated air will make the combustion instantaneously.

I will give my experience about heater plugs. Some engines have only one heater plug fixed to inlet manifold that is manufactured to battery voltage or little lower then that enable to driver to see the glow heater on the dash board panel to see that the heater indicator wire coil till get red hot before you apply the starter motor to start engine.

Some are 1.5 volts to 2 volts heater plugs, they are wired in series to your electrical wiring system with a glow indicator on your dash board panel.Then there are electronically controlled heater plugs in newer vehicles only with a indicator bulb on the dash board.

They go off to the programed time, when the engine get under compression, some drivers on and off the heater position of the IGN switch, so that glow plugs will be heated for longer time before they operate the self starter motor of the IGN switch. I have experience of that way and advised number of diesel newer automobile users to do that in the morning for electronic timer fixed engines. This above method was a temporary thing till they go for a engine overhaul.

You can still start your engine without the heater but it will take longer time and your self starter motor will have to work long working time depending on your engine condition.

If your engine is low compression then you cannot start even after heating then you will have to start with a push start.

If you want any more explanation on the above please do post till you get satisfactory answer to your question.Can give you more advice on the difficult cold start of your engine.

Sylvi Wijesinghe.

Thanks to Sylvi and harshansenadhir, Both of you have given a very good explanation. As harshansenadhir said the heating system is manual and have to turn the ignition key to anti clock wise & the indicator is right above the ignition key(which is also manually can see. - not a bulb) and we can see it's getting heated. Mine it takes about 18-30 secs in the morning to heat properly. I was thinking that it is the correct time duration it takes but 'Ripper' said it has to be around 5 seconds. So is there anything that makes it take little longer?

(Anyway I have to get it checked). The engine is in a very good condition and i serviced the injector pump recently and replaced the nozzle and replaced the batteries as well.