So drove the truck up to the shop fine started great always has shut it off went to start it a couple hours later no start no smoke out the exhaust glow plug light still comes on, relay 303 is chattering probably 10 times a second I pulled it out and there is something else chattering in the back of the fuse box I suspect it’s the fuel pump relay that’s built in but I’m not sure on that, no fuses are blown and the high current box under the hood is cleaned up still nothing, changed pcm with a 422 this truck had a 462 I read on here that the truck should start with that just loose gauges but still a no start, I unplugged the fuel bowl heater and checked fuses still nothing, changed the cps to a dark blue/purple one still nothing, the fuel pump under the frame rail is working when I turn the key on, battery posts are cleaned and I have another truck hooked to boost because while turning over it only has 8.5 volts which concerns me a bit but I can’t seem to find a way to get it any higher, also I tried unplugging the icm or whatever the sensor on the driver side rail at the front of the engine is called still nothing, I’m thinking this might be an idm issue but from I’ve read they slowly die out or will still fire on one bank of cylinders any help would be appreciated

edit:also it has good oil pressure while turning over, and plugged a good quality scanner in and it’s telling me it can’t connect to the computer

 

Rapid clicking is one symptom of weak batteries and I believe that 8.5 volts is not enough to light it off. Charge and test the batteries and ensure that your connections are clean and take it from there.