Welcome to our site
You wake up early on a winter morning and head out to your truck to go to work. It's been getting a bit tougher and tougher to start as the weather gets cool, but, today, with the temperature approaching zero Fahrenheit, the truck just cranks and cranks and never fires. Chances are, your glow plug system is failing.Glow plug troubleshooting and repair is fairly easy and not too expensive. Taking your truck to the dealer for this service can cost well over a thousand dollars while you should be able to do the work yourself in a few hours for less than two hundred dollars.
Unlike gasoline engines that use spark plugs to operate, diesel engines operate by compressing a fuel and air mixture. When a gas is compressed its temperature increases. The extremely high compression ratios of diesel engines raise the heat of the fuel-air mixture to the point of ignition through pressure alone. However, at very low temperatures this compression isn't enough to cause the fuel to burn. This is where the glow plugs come in.
The glow plugs are heating elements in each cylinder, which provide a very hot point that raises the temperature of the fuel-air mixture to the point of ignition. If one or two of your glow plugs have failed you might notice your truck is a bit hard to start on cold mornings. If more than that have failed it might become impossible to get your truck going.Troubleshooting of the glow plug system is fairly straightforward. All you will need is a multimeter to measure resistance and voltage and, possibly, depending on the design of the probes on your meter, some straight pins or something similar to test the glow plugs themselves. You will also need a couple of pieces of jumper wire about two to three feet long, preferably with alligator clips on each end.
The first thing to test on the system is the glow plug relay. This relay is a common point of failure. The glow plug relay is located on top of the engine right behind the fuel filter housing and slightly to the passenger side. If there are two relays located there it will be the relay toward the back of the vehicle with large yellow and brown wires leading to and from it.
To test the relay you want to check the voltage at both large terminal posts right after turning on the truck. The glow plug relay should activate for 10 seconds or more, no matter what the temperature, longer when it is colder. You might wish to have someone turn the key to start while you have the meter on
don’t hold back The Official Jeep Site: Take a test drive today - Don't Hold back