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1993 6.5 automatic 4wheel drive long bed

nealpellecchia said:
I unplugged the cold advance fast idle circuit cranked the engine..did not stary...and it blew the ECM fuse 10Amp.
Click to expand...

My vote for next steps is to clean the grounds at the rear passenger side of the block / valve cover (presuming that the PCM's ground is at that location) and add a wire from that location to the battery.
 
cold advance is a stand alone. unplugging a stand alone to diagnosis a connected is a waste of time.
 
nealpellecchia said:
Do weak grounds draw more juice?
Click to expand...

I provide examples of a unrelated problem, cold advance, so you can try similar things to find the dead short. I forget what fuse was blowing but it didn't affect the transmission.

My point is a test light across the blown fuse and wiggle the harness or disconnect things on the circuit till the light flickers or goes out. The light being "on" indicates a fuse blowing dead short. When it goes "off" the short condition is gone. Whatever was just unplugged when light goes off has issues. Same with moving harness - light goes off you found an intermittent short. Note rare cases the wires could have melted and fused now so moving the harness may not show the trouble area.

Weak grounds float the voltage of the entire circuit up. It's like a resistor in the circuit. More current means there is more voltage across the resistor, bad ground. Eventually there isn't enough voltage to allow a computer to make a "0" a "1" and it screws up. Solenoids don't work and esp. the lift pump won't pump with low voltage and lack of current. Of course the lift pump is just an example of low voltage and current due to high 'bad' OPS contact resistance.

With these trucks checking the critical ground is always a good idea no mater how casually it may or may not be related.
 
I see on 1994+ trucks the fuel heater is on the ECM fuse. Can't find a 1993 diagram to confirm so you may look there for crispy wires or just disconnect it like @ak diesel driver suggested.

And ran across old posts: The fuse I was having trouble with for cold advance shorted was the "Gauge" fuse. Only took me 3 days to find it. :facepalm:
 
WarWagon said:
I provide examples of a unrelated problem, cold advance, so you can try similar things to find the dead short. I forget what fuse was blowing but it didn't affect the transmission.

My point is a test light across the blown fuse and wiggle the harness or disconnect things on the circuit till the light flickers or goes out. The light being "on" indicates a fuse blowing dead short. When it goes "off" the short condition is gone. Whatever was just unplugged when light goes off has issues. Same with moving harness - light goes off you found an intermittent short. Note rare cases the wires could have melted and fused now so moving the harness may not show the trouble area.

Weak grounds float the voltage of the entire circuit up. It's like a resistor in the circuit. More current means there is more voltage across the resistor, bad ground. Eventually there isn't enough voltage to allow a computer to make a "0" a "1" and it screws up. Solenoids don't work and esp. the lift pump won't pump with low voltage and lack of current. Of course the lift pump is just an example of low voltage and current due to high 'bad' OPS contact resistance.

With these trucks checking the critical ground is always a good idea no mater how casually it may or may not be related.
Click to expand...
Very good info.
 
WarWagon said:
I see on 1994+ trucks the fuel heater is on the ECM fuse. Can't find a 1993 diagram to confirm so you may look there for crispy wires or just disconnect it like @ak diesel driver suggested.

And ran across old posts: The fuse I was having trouble with for cold advance shorted was the "Gauge" fuse. Only took me 3 days to find it. :facepalm:
Click to expand...
You say," on the ECM fuse". the 93' 6.5 is on the 20amp gauges fuse which looks like is connected to the 10amp ECM fuse on the back of the fuse block.
 
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