This diode is now resin potted to protect against breakage.
For 12valve engines, years 94 to 98-1/2
Fuel solenoid failure almost always begins with worn starter contacts. When a starter sticks on it is caused by the worn contacts arcing and becoming welded together. When this happens the starter back-feeds 12v up through the trigger curcuit to the 70amp fuel solenoid relay. The relay then thinks it getting the power from the ignition switch so closes the relay and energizes the fuel solenoid via the "pull" coil. This is why the engine won't shut off by the key. This "pull" coil is very strong but low resistance so will overheat very quickly if allowed to stay energized. This is what causes the fuel solenoids to burn up.
So, by installing this one-way diode and preventing the starter from backfeeding the fuel solenoid curcuit we save the fuel solenoid from burning up if the starter sticks on and also allow the engine to be turned off. Again, this is the primary cause of fuel solenoid failure. A diode lets current flow one way but not the other.
Easy to install, takes about 5min.