When i turn the key the 20amp inline fuse behind the battery of my 1989 305 tbi blows. when i disconnect the pigtail under the car to the fuel pump and turn the key the fuse does not blow..?

**Is this a possible fuel pump pigtail has a short?How can i disconnect this without dropping the tank? Car doesnt start.

 

pics

 

Fried Fuel pump.

 

I had similar issues. Wouldn't get power to the fuel pump, First check the inline fuse behind the battery, second, check your fuel pump relay, i had frayed wires on my oil prssure switch, when jumping it over my fuel pump kicked on. Replaced the switch and bandaged the wires and badabing, starts everytime. Fuel pump should be the last thing you try, and if you do it's well worth cutting the access hole in the trunk vs. dropping the whole rear accel and tank. I hope all this helps.

 

I would not jump to conclusions at this early stage.

If disconnecting the C313 above the differential prevents the fuse blowout, the wiring past the C313 is in question. I would connect an ohm-meter to the outside two pins (A and C) and measure resistance in the 20 ohm range. You should see approx. 6 ohms for a good fuel pump.
If you see 0 ohms, there's a short somewhere but not necessarily in the pump. The wiring might be exposed either on the inside or outside and shorting out. I would recommend a good inspection mirror, a bright light and a great dose of patience.
If visual inspection does not reveal any wiring trouble on the outside wires, you might need to resort to dropping the tank.
Which in itself is not as hard as one might fear. It really depends on the attitude. I have replaced fuel pumps in under 4 hours before, with just one helper. And you might not have a bad pump (they rarely short out), it would be as simple as a chafed wire on the inside of the tank.

But let's hope that you find something before you get to the pump.

Let us know what you find.
Lou

 

My fuse behind the battery was blowing because the oil pressure switch wires had a short, after replacing the connector, ops, and the inline fuse everything works exactly like it should. A lot of garages blame the ecm in these cars but its rarely that. Good luck