- Diesel Engine Tips (page 3) by P.B.Gill
The Glow Plug system should be tested before the cold weather arrives , on diesel vehicles over three years old .
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The glow plugs preheat the engine cylinders and pistons prior to starting the engine . This enables the engine to start in cold weather and also prolongs the life of internal engine parts . Preheating lessens the severity of the sudden increase in the temperature inside the cylinder from combustion of the fuel mixture . Some diesel engine may use an air intake heater as well as a glow plug system . Other vehicles may use an air intake system in place of a glow plug system . If these systems are functioning properly , starting in cold weather will be no problem .
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Most glow plug systems work on a total resistance , timed system strategy . If one glow plug fails to operate (burns out) the system ‘on time’ will be shorter . This means that you would notice the indicator light comes on for a shorter time . If two glow plugs are out the ‘on time’ will be even shorter , and so on . If you notice the glow plug light (or wait to start light) is coming on for a shorter time and the engine take longer to start , the glow plug system should be tested and repaired as needed . If you see white smoke from the exhaust (tail pipe) when cranking the engine to start or just after the engine starts , this is also a sign of a glow plug system (or air intake heater) malfunction . In most cases the glow plug system on a new vehicle will operate for two or three years or more before new glow plugs are needed .
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When a glow plug burns out due to age and usage it is best to replace them all , as they are all the same age . This will save you inconvenience and down time as well as expense in the long term . If the glow plugs are under the valve covers it is best to replace all the glow plugs that are under that valve cover (on that side of the engine) . The main labor expense is to remove and install the valve cover , so replacing all glow plugs under that cover will save you money in the long term .
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See Diesel Cold Start tips - diesel engine tips page 4 .
