Attention: TDR Forum Junkies 
Some recent posts about the fuel solenoid circuit mentioned the fuel pump and automatic shut down relays. I didn't think we have them on our diesels. Just to make sure I looked in the PDC. Lo and behold there they were! Now I wondered (I get in trouble this way) what are the functions of these two relays? Careful examination of the wireing diagrams in my trusty (?) service manual revealed that I have a fuel pump in the tank. If I have one it is a little hard to see when I have the sending unit out so I think my trusty manual has a problem. I traced all the wires in the diagrams involved with both relays and could not find anything that they did. There was something about setting a code if the ASD relay did not energise when it was supposed to. Other than that the relays appear to be just along for the ride. So I removed both of them to see what might happen. Started up the truck and everything worked like it always does. Didn't even set the code as far as I can tell.
There are six relays in the PDC if you don't have four wheel ABS and eight if you do. They are all the same part number. So if any of the useful relays (starter, A/C clutch, horn, trailer) fail just use one of the those that are just along for the ride as a replacement.
There are six relays in the PDC if you don't have four wheel ABS and eight if you do. They are all the same part number. So if any of the useful relays (starter, A/C clutch, horn, trailer) fail just use one of the those that are just along for the ride as a replacement.
