I have a 1985 ford f350 diesel.It keeps burning up the autolite glow plugs.do you know why?

Check GPR operation--it may not be clicking off, when it should, and the glow plugs are burning out.

Here's how it should operate:

Check glow plug relay (GPR). Ensure the engine is cold, so that the PCM will tell the GPR to turn on. If the engine is hot, you won't have as much time to check. Locate the GPR, which is often behind the fuel filter on top of the engine, slightly toward the passenger side of the valley on PSDs. There may be two relays there. If so, the rear relay is the GPR. It should have two fairly large wires (Yellow and Brown) connected to one of the large posts. With multitmeter set to DC volts, or 15V range if not autoranging, clip the positive (Red) lead to the output terminal (with yellow and brown wires connected), and the negative (Black) lead to ground. Turn the ignition switch to ON. If the GPR is good, it should click, and you should see 11 volts or so on the meter; then, depending on temperature, it will click off up to 2 minutes later. Do this a couple of times, to ensure it consistently makes the connection. If there is no voltage with this test, confirm by retesting as follows. Remove the two small wires from the smaller two of the four GPR terminals. With jumper wires, apply voltage from the battery across the two small terminals. If the voltmeter now reads voltage on the output terminal, the GPR is good and the problem is in the PCM circuit that tells the GPR to activate.