Originally posted by Mopar-muscle:
pre 2000 trucks are 1/8 npt on the ports on top of the filter cannister as csutton described , 2000 and newer use a schrader valve which is the same as a -4AN , but it has a valve much like that in a tire valve stem that is released when you have the proper type adaptor that screws on . if you don't have the proper adaptor then you need to remove the valve core , same tool as a tire valve stem core remover and then screw your -4 to 1/8 npt adaptor over it and connect the gauge , if you do it at the injection pump , removing that core will drain the pump and you'll need to bleed it to get it running .
i have seen an aftermarket test gauge setup with the adaptor that will allow you not to have to pull the valve core , but its pricey , the tool from miller that the factory uses is fairly cheap , don't have it handy to post the number but i will get it if people want to buy that gauge .
should see above 10 psi idle , more like 12-13 ... and would be nice to see 10 while cruising , but you won't , and nice to see more than 6 WOT , but you won't , depending on BOMBs installed and if you have the factory pump or a replacement .