blowing fuses

[muskieking2001]

my 92 safari blows the fuel pump fuse when it is put in. can anyone help where to look first.

[Blue Bowtie]

The first and most obvious answer would be to look at the fuel pump.

However, beyond checking that, and since the pump should not be operating if the ignition is off, a quick loook at the schematic for it would be helpful. The 20A fuse that protects the pump circuit also powers the ECM on your van. In the hope that the ECM does not have some catastrophic problem (which could be due to an overvoltage spike), the fuel pump circuit is the prime suspect.

One possibility, and the easiest to check, is that the fuel pump relay has become damaged and is shorting the power supply to ground. Heavy arcing or moisture in the relay could do this. You can unplug the pump relay and either risk wasting another fuse or meter the resistance of the pump circuit to ground. You should have at a minimum 2K ohms to ground due to the ECMs fuel pump voltage monitoring circuit. More likely it will be in the 100K + range. If the resistance is within that range, install a fuse and see if it holds. If so, you likely have the failed part already removed (relay).

If the resistance is still below 2K ohms (or more like just a few ohms) you need to remove the doghouse and check the wiring at the auxilliary oil pressure switch at the rear of the engine, just below the distributor. It will receive power via this fuse even with the ignition off. If the wiring is pinched or damaged, it will short the supply to ground. If the switch itself is damaged, it can do the same thing. If the wiring appears to be intact, unplug it from the switch, isolate the connector, and check the circuit resistance again. If the resistance is now 2K ohms or greater, the fuse should hold with the pressure switch disconnected, and the oil pressure switch is suspect.

[muskieking2001]

i disconnected the harness to the pump and it still blows. i not sure which one is the relay is it one of the 2 above the blower motor?and thank you for your help

[Blue Bowtie]

The position can vary depending upon how the vehicle was assembled. You should be able to identify the fuel pump relay by the wire colors in the socket. There should be a larger diameter orange wire, a large gray or tan wire, a red wire, a dark green/white striped wire, and a black or black/white striped wire. The other relay should be for the blower high speed so if you're in doubt, you can disconnect them both.

If you're lucky, it's only a relay, but I'm guessing you may find the problem near the rear of the engine - Just a wild guess, though.