Chevrolet Repair: ecm b fuse problem, plug fuse, fuel pump relay

Question
QUESTION: I have a 96 3500 hd 6.5 diesel cab and chassis with roll back body, the ecm b fuse started blowing in the middle of a load. if i replace the fuse it does not blow until i crank the engine, if i use a jumper temporarily to start it then switch back to fuse it starts fine until i shut it off and try cranking it again. I have tested voltage at fuse and it stays at 12v until cranking them drops to 9v once it starts it goes back to 12v. since it stays running i assume that my fuel pump is fine. the fuel gauge is all over the place so i know it is not grounding out. any ideas where to start.

ANSWER: HI AARON,THIS TO ME SOUNDS LIKE SOMETHING IS REALLY PULLING ALOT OF AMPS. THE ECM FUSE POWERS UP THE FUEL PUMP RELAY AND MANY MORE FOR THAT MATTER. I DO NOT HAVE A WIRING DIAGRAM FOR THIS. WHAT I WOULD SUGGEST IS REMOVING THE FUEL PUMP RELAY AND COLD START INJECTOR RELAY. [GLOW PLUG CIRCUIT] ONE AT A TIME PLEASE, AND THEN TRY TO CRANK IT OVER,I KNOW IT WILL NOT START, BUT IF THE FUSE DOES NOT BLOW THEN I WOULD THINK THE PROBLEM IS ON THAT CIRCUIT,OR YOU COULD REMOVE ALL THE RELAYS AT ONCE AND CRANK OVER AND INSTALL ONE RELAY AT A TIME TO SEE WHICH RELAY BLOWS THE FUSE WHEN PUTTING IN ONE RELAY AT A TIME..... I HOPE THIS HELPS YOU,IF YOU CAN GIVE ME MORE INFO AS YOU CK THIS OUT FURTHER GIVE ME A YELL.. THANKS TOM

---------- FOLLOW-UP ----------

QUESTION: pulled both the fuel pump relay and the glow plug fuse, try to crank it and it did not blow, replaced fp relay and it blew, removed relay and installed glow plug fuse and it did not blow, so i am guessing i either have a short in wiring going to puel pump, or relay or pump is going out.

Answer
HI AARON, MY MONEY IS ON THE FUEL PUMP,PULLING TO MANY AMPS TO START UP!!!I HAVE NEVER SEEN A RELAY CAUSE THIS..YOUR SECOND GUESS MAYBE CORRECT ABOUT A SHORT TO GROUND BUT I WOULD THINK THIS WILL HAPPEN EVEN WHEN DRIVING AS WELL AS FIRST START UP. IF YOU HAVE A AMP METER YOU COULD SEE HOW MANY AMPS THE PUMP IS PULLING WHEN IT FIRES UP. RULE OF THUMB IS 3 TO 4 AMPS LESS THEN THE CIRCUIT FUSE. ANYTHING OVER THAT TO MUCH RESITANCE...IF YOU NEED MORE INFO GET BACK TO ME.. THANK YOU FOR THE RATING. TOM..