1. Hard starting. A hard starting engine is the most common indicator of damaged glow plugs. In cold conditions, without correctly functioning glow plugs, the combustion chamber may not reach the right temperature to ignite the fuel and start the engine. If there are no problems with the fuel or the battery, then glow plugs should be checked. 2. When the glow plug doesn’t heat atomized diesel enough, it causes engine misfire. That means the glow plug can’t ignite fuel in the chamber. In addition, the combustion chamber is likely to get flooded with diesel fuel. That means your car will have reduced power output until the remaining fuel is burned. How Glow Plugs Work. Just like each engine cylinder has spark plugs in petrol-powered engines, each cylinder in a diesel-powered engine also has glow plugs. Yet, they are very different in functionality. While the spark plugs create combustion by igniting air and fuel, glow plugs warm up the combustion chamber. Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - glow plug problems on 6.9 - I'm new to the forums and need some help. I've read everything but still in the dark a bit. I have a 1987 f-250 with 6.9 diesel and it has 220,000 miles on it. It has the later version controller and relay on the rear of the intake. The glow plugs on a diesel engine will typically last around 100K miles, but they can fail before then. Here are a few signs to look for that might signal your glow plugs need to be replaced. 1. Hard Starting. If a glow plug has failed an engine can struggle to start. In cold conditions, the combustion chamber may not reach the required Dec 31, 2020. #14. If it won't start in this weather due to the glow plugs all being dud then you're really not going to make a difference with a hair dryer or sticking burning rags in there. It sounds like there is an underlying issue besides the plugs. It's cold sure, but nothing like proper cold. Glow plugs warm the combustion chamber and the atomized fuel. Up until tier 4 emissions most off road Cummins engines had no grid heaters and still started at below zero temps. This is also the case with some folks who’ve deleted their grid heaters. They still start at below zero temps. Try that with a glow plug equipped engine. A grid heater is an element like an electric kettle has inside or a stove. Current passes through the HEAVY GUAGE wire and turns it red hot, so it heats the air. So when you start your motor on the intake stoke the vacum sucks the HOT air and assists the combustion. Im my opinion way more efficient than glo- plugs. As you are aware, diesel engines do not have spark plugs. That is because diesel fuel ignites differently than regular gas does. If you have a diesel engine, you have glow plugs to help start the motor. The glow plugs are best when you are cold starting your vehicle. Since Duramax is a diesel engine, there will be glow plugs inside warming the Big engines don't need glow plugs because they have a lot more swept volume in relation to the surface area of the combustion chamber. This means that less of the heat generated in compression "leaks" away into the cold cylinder walls and head. This also explains why a 6.0 liter PSD needs glow plugs while a 5.9 liter Cummins does not. uaHm1.