I noticed this with my 6.2 and did some research. According to Mitchel on Demand, " a normally operating system works as follows; at room temperature and with ignition on and engine off, the glow plugs come on for 4-6 seconds and the go off for about 4.5 seconds. The glow plugs then cycle on for about 1.5 seconds and off for about 4.5 seconds, for a total start sequence of about 20 seconds. If the engine is cranked during or after start sequence, the glow plugs will cycle on and off for about 25 seconds after the ignition switch is returned from the crank position, whether engine starts or not." What all that info means is that it all comes through the cold advance control and the temp sensor in the rear of the left head. I changed the sensor and start-up is fast now and the glow plug cycle is the same as it was before. I thought I'd have get some plugs and decided to try this cheap way first and it worked. Theres a complete theory and operation in the mitchel on demand that prints out nice and helps greatly. Most small auto shops have this and I'm sure they wouldn't have a problem printing it out for you in exchange for some cold lagers.