Unknown Short Circuit

[nola mike]

@muc right, temp switch would need to be bad (closed when cold) for a short in p/y to blow that fuse.

 

[muc]

@muc right, temp switch would need to be bad (closed when cold) for a short in p/y to blow that fuse.

The blocking diode would also need to be shorted then yes.

 

[nola mike]

When I started troubleshooting the orange wire to the fuse had continuity to ground which would mean the temp switch is in the closed position when engine is cold. Is that the correct position?

No it isn't. Again, disconnect temp switch. Test it directly. Hopefully you're making sure there's no power in the circuit you're testing for continuity.

My logic is Since this circuit feeds the oil pressure switch (assuming this switch has a normally closed position) then the short could be on the alternator or coil?

Incorrect. Alternator and coil have nothing to do with this circuit, as mentioned. Op switch doesn't work that way, it's a mechanical switch.During starting power is applied to y/p from the starter solenoid. Once key is released to run position no power is supplied via that route. When oil pressure rises, op switch closes and connects purple (from ignition circuit) to p/y, which then goes to fuel pump and diode to tks module. When temp switch closes, power is applied to the tks module via your fuse. So when the engine is warm, power is still applied to the module, keeping it open and preventing it from enriching the mix.

 

[04fxdwgi25]

Blocking diode is like a check valve. Only allows voltage to flow in 1 direction and blocks flow in opposite direction. Hence why it is used on the fuel pump circuit. Allows starter circuit to power fuel pump, but once started, blocks the ignition circuit from powering starter solenoid, after starting.

If blocking diode goes shorted, starter would continue to be engaged after key is released. If it goes open, no fuel on start until oil pressure comes up..

 

[muc]

Allows starter circuit to power fuel pump, but once started, blocks the ignition circuit from powering starter solenoid, after starting.

If blocking diode goes shorted, starter would continue to be engaged after key is released. If it goes open, no fuel on start until oil pressure comes up..

NO…….
This part of your post is completely false.

 

[plush82]

I know this may not help but I wanted to share a similar situation I was going through, my 03 3.0 would blow it's key switch fuse the second I turned key to power, tried to start, or sometimes a few seconds after getting running. It ended up being the shift interrupt wire smashed in between the mounting bracket when I had loosened the bracket to change the valve cover gasket, I kept changing fuses and rewired my key and switch connections under the dash before I found the wire with just a slight knick in it at the motor. Loosened the shift interrupt bracket, pulled the wire and wrapped it in electrical tape and haven't had a single issue since.

 

[nola mike]

I know this may not help but I wanted to share a similar situation I was going through, my 03 3.0 would blow it's key switch fuse the second I turned key to power, tried to start, or sometimes a few seconds after getting running. It ended up being the shift interrupt wire smashed in between the mounting bracket when I had loosened the bracket to change the valve cover gasket, I kept changing fuses and rewired my key and switch connections under the dash before I found the wire with just a slight knick in it at the motor. Loosened the shift interrupt bracket, pulled the wire and wrapped it in electrical tape and haven't had a single issue since.

This is not the OPs problem.

 

[04fxdwgi25]

NO…….
This part of your post is completely false.

????

Please explain

 

[nola mike]

????

Please explain

If the diode is shorted closed, current flows backward through the op switch into the ignition (purple wire), so engine won't turn off when the ignition switch is turned off. Starter is engaged through the yellow/red wire, not anything on this circuit. If shorted open no current flows to the tks module until the temp switch closes, so it will run rich until then

 

[04fxdwgi25]

If the diode is shorted closed, current flows backward through the op switch into the ignition (purple wire), so engine won't turn off when the ignition switch is turned off. Starter is engaged through the yellow/red wire, not anything on this circuit. If shorted open no current flows to the tks module until the temp switch closes, so it will run rich until then

OK, thanx for the clarification. I got it. I said starter instead of ignition.

Have seen fuel pump prime functions that bypassed the oil pressure switch during starting installed in some applications. Power to the fuel pump is maintained, through oil pressure switch, once oil pressure builds and starter is released. A blocking diode (or relay circuit) was used to to prevent back feeding the starter circuit when oil pressure switch was closed.

But basic function of the diode part was correct.