How can I tell if my truck fast idles?

[m1garand_man]

How can I tell if my truck fast idles? I'm not sure if mine even dose. If it dose I cant hear a difference in the rpm's from the 625 low to the 800 high. I know this only happens when the engine is cold and even then I cant tell any difference.

 

[91W350]

If it is working right, you will definitely know. You can feel it kick off with your foot when you are driving down the street. It should advance the timing at the same time. The diesel knock is much more pronounced when the fast idle is on. The warmer the ambient temperature, the shorter it lasts. On very cold days I can make the two mile drive to work and never have it kick off. On really hot days it will kick off before I reach the end of the block, occasionally before I get backed out of the driveway. All three of mine are about the same in characteristics as was my previous M1008. Glen

 

[m1garand_man]

so when I first start it and it sounds crappier and louder as it idles and when I drive it it's high idleing?

I took a look at the screw on the fast idle solinoid today when I started it it didnt move. I tried pulling and pushing on it to see if it was supposed to move or what would happen. It will pull out about 1/16" and there is no sound change and you can push it in and it dosnt seem to move and the idle only sounds like it maybe picks up 25-50 rpm. its hardly discenrnable.