Here we go. My 1986 M1028 has been reliable for 9 years. Then it had starter issues. Noticed the negative battery cable from forward battery was very hot after each start attempt. I replaced the starter, both batteries. I cleaned both bus bars, checked all battery cables and cleaned. All 4 battery clamps had been replaced before and look solid. I removed and cleaned the main engine ground stud, sanded to bare metal and reinstalled wires. Did same to forward battery frame grounding points. Turn key and same click. No start. Verified starter solenoid is engaging by sound and feel. Now burned the starter relay. Replaced it and with an AC40 and burned it. Wires getting hot from relay now. Checked voltages at relay. All ok and ignition switch provides 12 volts when key turned to start. I did jump the relay's 24v wires to bypass the relay. I heard the starter solenoid clicking but no starter turn. The new starter is aftermarket, gear reduction from Amazon. 2 year warranty. I did not bench test the new starter. I did test my old OEM starter, the solenoid engages but it doesn't spin. I have another old OEM starter which does test ok. I didn't install it because it looked rough and I wanted something newer. Our local electrical shop told me they can't get some parts to do a rebuild if the armature, etc is bad. Said they would use my two starters for parts to rebuild one for $200....So, I am thinking of removing the new starter to test it. How can I verify if a fusible link is bad? Where are they? And what should be my next course of action? I did get the Doghead relay at O'Reilly's and haven't done the mod yet but will. Any advice is welcome. This truck is used in parades, hauls furniture, you name it. 22k miles on it. Wiring looks just fine. It was an M1031 convert to M1028 radio truck. You can see where the engine compartment governor unit was removed.
, YMMV.