Dodge Diesel - Diesel Truck Resource Forums - Solid state relay puts an end to many starting problems

I have two '95 2500 automatics that I bought used with about 100k on each. When I bought the first one three years ago, I soon found it had the common "failure to pull in the fuel solenoid" problem. After much trouble-shooting, I found the cause was a poor ground from the neutral saftey switch on the transmission. All switches have some impedance, but on my trucks, these now read about 3.5 Ohms. I have no idea what they conducted when the truck was new. When this impedance develops in the switch and/or in the plug on the switch, it can prevent the starter relay from pulling in strongly. As the starter starts cranking, there might not be enough current available to pull in the fuel shutdown relay (on the firewall)and energize the fuel solenoid. The engine cranks but gets no fuel. This can happen intermittently. It might start right up the second time, or after a half hour or so. It might not act up for months, but you never know when it might happen again. You're lucky if you don't change expensive parts in the meantime that don't cure it permanently. I stopped it by cutting off blade No. 85 of the starter relay, drilling into the base of the relay and soldering a wire to 85. I brought this wire out of the PDC and to a ground screw on the fender. The result was reliable starting, but neutral saftey function was lost. The trucks would start in drive or reverse. The design of the linkage makes this unlikely, but it has happened a few times at the drive thru restaurants.<br> When one truck had a serious electrical fire recently I had to study the entire electrical system to find the cause (bad starter motor and lack of proper bonding on D-C's part) and I started thinking about a better way to modify the starter relay. I found a solid state 40 Amp relay that fills the bill. The health of the neutral/saftey switch ,or the clutch switch in a manual, don't matter now, as that circuit only has to provide a signal to the relay, not pull in a contact. The relay itself fits in the PDC and short wires with terminals plug into the starter relay connections. It works perfectly!<br> Now you can have reliable starting and full clutch or auto saftey operation. These relays are expensive, but made for millions of operations and should out last several engines. A stock starter relay that is not functioning properly will shorten the life of the starter solenoid and motor and the fuel shutdown relay. More details to follow soon.<br>