Engine fuse keeps blowing… I’m lost (1 Viewer)

[theodore1]

Hi there I have a BJ73 with the 3B motor, occasionally when I was driving the engine fuse would blow, and now the fuse blows every time I turn the key to the on position. I have tried disconnecting starter, starter relay, glow plugs glow plug relay, tail lights radio, fuse keeps blowing and blowing. Has anyone had this problem I need to get it on the road.

 

[jmylie]

Mice chewing on wire insulation? Bare wire making contact with metal causing the short. Follow the wiring harness as best you can to see if you can find the short.

 

[Felde]

Hi
That's a hard gremlin to hunt..
1st get a bulk of fuses. Do not try to jump fuses or go with bigger capacity. That wouldn't help on the problems but might well do great damage.
2nd check your grounds. You may use Jumper cables to temporarily setup good grounds during the troubleshooting. You need to cover frame (front, rear), engine (engine mounts isolate!), gearbox and starter.
As advised in your other thread and as you already started: Disconnect stuff from the circuit and try to find the subcircuit of issue.
Pull the relays. Pull all other fuses. Free up the fuse box to look at it from the back. Working systematically is key.

You say, it always blows the fuse when turning the key? At which position?
The 1985 key switch has 3 positions.: Position 1 already provides power to things like dashlights, lighter, radio. Position 2 is 'ignition' / engine-run, Position 3 is starter. Try to identify which of those circuits blows the fuse. Go from there (see wiring diagram).
It is well possible that even the switch itself is the culprit.

If you need a wiring diagram: Let me know (I have all manuals for the BJ73 1985 )
Positions of relais can be seen in the parts diagrams, too.
Good Luck Ralf

 

[theodore1]

Hi
That's a hard gremlin to hunt..
1st get a bulk of fuses. Do not try to jump fuses or go with bigger capacity. That wouldn't help on the problems but might well do great damage.
2nd check your grounds. You may use Jumper cables to temporarily setup good grounds during the troubleshooting. You need to cover frame (front, rear), engine (engine mounts isolate!), gearbox and starter.
As advised in your other thread and as you already started: Disconnect stuff from the circuit and try to find the subcircuit of issue.
Pull the relays. Pull all other fuses. Free up the fuse box to look at it from the back. Working systematically is key.

You say, it always blows the fuse when turning the key? At which position?
The 1985 key switch has 3 positions.: Position 1 already provides power to things like dashlights, lighter, radio. Position 2 is 'ignition' / engine-run, Position 3 is starter. Try to identify which of those circuits blows the fuse. Go from there (see wiring diagram).
It is well possible that even the switch itself is the culprit.

If you need a wiring diagram: Let me know (I have all manuals for the BJ73 1985 )
Positions of relais can be seen in the parts diagrams, too.
Good Luck Ralf

Hey Ralf thank you so much, I would love to see a wiring diagram that would be a huge help. Fuse blows on the second position it seems.

 

[Felde]

Hey Ralf thank you so much, I would love to see a wiring diagram that would be a huge help. Fuse blows on the second position it seems.

PM sent with link to manuals.

I was afraid it would be on key position 2, as this is where most the consumers are attached to.
If proper ground , e.g by jumper cables, don't help, it's a wire in the harness.
As it doesn't blow the fuse with key off, the issue must be behind the keys switch (or in it).
Use the wiring diagram, isolate the stretches keyswitch-consumer (or switch or relay for the consumer), one by one. Only consumers on the blowing engine fuse are suspects. Switches and relays are suspects, too. So make sure you disconnect those from their inbound wires.

You may want to take the key switch out of the game (pull connectors) and bridge the various lines manually with a small jumper wire, one by one within the connectors, rather then having the key switch bridging all lines at once. But that requires a solid understanding of the wiring diagram and wire colorcodes.

Likely it is a broken insulation that grounds short circuit to a metal body part. If there was no smoke / burnt smell (use your nose), two exposed wires that interconnect are not likely. Means: The wire of concern is likely to be on the outside of the harness bundle. Check the edges where the wire goes around body edges or passes holes in the dash.
Wiggling the bundles or connectors may relocate the damaged spot and move it away from where it short circuits. Wiggle it systematically and check after each move. Remember: Digging into it to unplugg consumers usually also involves wiggling. So really check after each move. Having the issue to disappear without actually having found the culprit wouldn't help, as another movemen could make it come back any time.
(You will blow a lot of fuses ... Automotive stores may have fuses (use correct spec or less) that can be reset. You may fab up a temporary resetable fuse)
Good Luck Ralf

 

[theodore1]

PM sent with link to manuals.

I was afraid it would be on key position 2, as this is where most the consumers are attached to.
If proper ground , e.g by jumper cables, don't help, it's a wire in the harness.
As it doesn't blow the fuse with key off, the issue must be behind the keys switch (or in it).
Use the wiring diagram, isolate the stretches keyswitch-consumer (or switch or relay for the consumer), one by one. Only consumers on the blowing engine fuse are suspects. Switches and relays are suspects, too. So make sure you disconnect those from their inbound wires.

You may want to take the key switch out of the game (pull connectors) and bridge the various lines manually with a small jumper wire, one by one within the connectors, rather then having the key switch bridging all lines at once. But that requires a solid understanding of the wiring diagram and wire colorcodes.

Likely it is a broken insulation that grounds short circuit to a metal body part. If there was no smoke / burnt smell (use your nose), two exposed wires that interconnect are not likely. Means: The wire of concern is likely to be on the outside of the harness bundle. Check the edges where the wire goes around body edges or passes holes in the dash.
Wiggling the bundles or connectors may relocate the damaged spot and move it away from where it short circuits. Wiggle it systematically and check after each move. Remember: Digging into it to unplugg consumers usually also involves wiggling. So really check after each move. Having the issue to disappear without actually having found the culprit wouldn't help, as another movemen could make it come back any time.
(You will blow a lot of fuses ... Automotive stores may have fuses (use correct spec or less) that can be reset. You may fab up a temporary resetable fuse)
Good Luck Ralf

This is a HUGE help thanks so much!! I’ll let you know how my digging is going