In April I replaced a fuel pump in my S10. When they replaced it , it blew a 20 amp fuse. They put in new fuse and it ran fine till this week. 5 months later. The fuel pump was bad and was replaced under warranty. It continues to blow fuse and they can't figure out what the problem is. Any suggestions?
My car has 160000 miles.
My car has an automatic transmission.
Fuses are over current protection devices which means that you either have a short to ground (possibly intermittent) somewhere in the circuit or enough added resistance in the circuit that the current drawn by the pump is enough to blow the fuse. You can use a volt ohmmeter to measure the current draw of the pump and see if it is within factory specified limits.
If you have a wiring problem, you can re-do (bypass) as much of the existing wiring as possible (i.e., re-wire the fuel pump circuit) because otherwise you will have to laboriously go over the entire circuit until you find the wiring fault.
You should also check to see whether the fuel pump is only device on the fused circuit. If not, check the other loads on the fuel pump circuit as those other loads could be causing the problem (the overload). To check that refer to wiring diagram in Factory Service Manual.
There is also the possibility of a physical (mechanical) restriction in the fuel pump tubing, filter and/or pick up causing the motor to overload and draw more current than intended. That’s why you should measure the actual current draw of the pump in normal operation to rule that out.
If you’re unable to perform these checks yourself, have a certified technician, like one from YourMechanic, come to you and diagnose the electrical problem firsthand for an accurate repair.