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Discussion Starter · #1 ·
Hi all, my 02 f250 psd 7.3 4x4 automatic won't start. I had a new starter installed a few weeks back and all was fine. Then the 30Amp starter fuse blew when starting. Did a bunch of troubleshooting and determined a bad starter. Dude at parts store tested the starter and said it was ok but traded it for a new one. Installed it and all was good for about 2 weeks, then the fuse blew again. I traced the wire and found a bad spot where it was rubbing on the front end frame. I have fixed that and replaced the fuse. Now the truck won't turn over. I can hear the relay click but no turns at starter. I get 12v on the coil side of the relay socket when I go to "Start" I have metered the circuit from the relay, thru the fuse link to the starter and it is good. I have 12v on the line side of the fuse but I can't read any volts on the common side of the relay socket, (term. 30). The schematics don't indicate any other components on the starter circuit. What can be interrupting this circuit? Thanks for your help. MM
 

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Discussion Starter · #2 ·
A follow up. I had tried starting the truck in "Park" and in "Neutral", thinking it may be the TPS. I tried starting the truck in drive and can still feel the start relay pull in. Does one of the other relays activate when the Trans position switch is in the proper position? This might explain why I have no voltage on the contacts of the start relay. How can I jump out the TPS to test the circuit? There are a bunch of wires at the trans and I have pretty crappy schematics for the truck. Thanks, MM
 

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If the relay is clicking, it's either bad contacts on the relay or something downstream of the relay that's preventing the starter from engaging.

Have you checked the wiring on the starter itself? A bad connection can cause it to fail to spin up. It could also be a bad ground, as the voltage fed to it has to get back to the battery.

Here's a diagram of the starting circuit.
 

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Discussion Starter · #4 ·
Thanks KL, I'll check the connection at the starter when I get back home. That is about the only thing I have not double checked. I made the connection without removing the starter, maybe I screwed up there. Looking at the schematic, there is nothing in the starter circuit to keep 12v off of the starter relay. The diagram shows that it is "Hot at all times". I can't see why I have no voltage on that terminal 30 of the relay.
MM
 
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