91 Cherokee blowing ECU fuse
 

A week ago I was driving home. I went up a big hill and the truck just
died and wouldn't restart.

I called a friend who towed me back.

When I checked things out, the ECC fuse (30A in the engine compartment
fuse block) was blown.

I replaced it and the truck started right up.

I let it run for a few minutes and went to move it up the drive way.
As soon as I "goosed" the gas, the fuse blew again.

This time I looked more carefully and noticed the plastic square tube
that carries the wires to the fuel injectors had come off it's mount
and was lying across the top of the motor.

I inspected it for any wires that might have arced (didn't find any)
and put it back.

I then replaced the fuse and it started again.

Now until I can figure out what happened, I'm afraid to take it out of
the driveway.

My question.

Are the inputs to the ECC (CPS, etc) protected in any way? or could an
intermittent short in one of the sensors cause the ECC fuse to blow
(nightmare). Or is this more than likely a bad injector. The Haynes
only shows the system in block form and didn't elude to fuses or links
for the inputs.

Any help would be appreciated as I want to start driving this truck
again

thanks

-bob-


This E-Mail is certified to be Virus Free by
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Re: 91 Cherokee blowing ECU fuse
 

"KoRn Kid® (Child of the KoRn)" <korn_kid_forever1@yahoo.com> wrote in
message news:r7i0a1dgstv8rv7jfhvkqg2vpi5mv4kaee@4ax.com...
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.

You didn't tell us whether you tried gooseing the gas...
I'm guessing (gooseing?) that you did, and that it
didn't repeat the performance.

Did the injector wires come close to the secondary
ignition wires? There's a condition called latch-up
where a FET junction can conduct catastrophically
given the right shock... maybe this happened.
Otherwise, just kill a chicken, ------ the blood
around the Jeep on the ground while saying the
appropriate mumbo-jumbo, and take it out for
a test drive, preferably with a cellphone (or ham
radio!) along.

40 amps doesn't normally flow to ground without
making some big holes... frankly, I'm suprised that
the ECU worked after replacing the fuse. Every
input and output in the computer chip is protected
with a diode to ground, and a diode to hot... perhaps
these saved you. Verify that you still get ignition
advance... it might be in limp-along mode.
__
Steve
..

Re: 91 Cherokee blowing ECU fuse
 

"KoRn Kid® (Child of the KoRn)" <korn_kid_forever1@yahoo.com> wrote in
message news:r7i0a1dgstv8rv7jfhvkqg2vpi5mv4kaee@4ax.com...
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.

You didn't tell us whether you tried gooseing the gas...
I'm guessing (gooseing?) that you did, and that it
didn't repeat the performance.

Did the injector wires come close to the secondary
ignition wires? There's a condition called latch-up
where a FET junction can conduct catastrophically
given the right shock... maybe this happened.
Otherwise, just kill a chicken, ------ the blood
around the Jeep on the ground while saying the
appropriate mumbo-jumbo, and take it out for
a test drive, preferably with a cellphone (or ham
radio!) along.

40 amps doesn't normally flow to ground without
making some big holes... frankly, I'm suprised that
the ECU worked after replacing the fuse. Every
input and output in the computer chip is protected
with a diode to ground, and a diode to hot... perhaps
these saved you. Verify that you still get ignition
advance... it might be in limp-along mode.
__
Steve
..

Re: 91 Cherokee blowing ECU fuse
 

"KoRn Kid® (Child of the KoRn)" <korn_kid_forever1@yahoo.com> wrote in
message news:r7i0a1dgstv8rv7jfhvkqg2vpi5mv4kaee@4ax.com...
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.

You didn't tell us whether you tried gooseing the gas...
I'm guessing (gooseing?) that you did, and that it
didn't repeat the performance.

Did the injector wires come close to the secondary
ignition wires? There's a condition called latch-up
where a FET junction can conduct catastrophically
given the right shock... maybe this happened.
Otherwise, just kill a chicken, ------ the blood
around the Jeep on the ground while saying the
appropriate mumbo-jumbo, and take it out for
a test drive, preferably with a cellphone (or ham
radio!) along.

40 amps doesn't normally flow to ground without
making some big holes... frankly, I'm suprised that
the ECU worked after replacing the fuse. Every
input and output in the computer chip is protected
with a diode to ground, and a diode to hot... perhaps
these saved you. Verify that you still get ignition
advance... it might be in limp-along mode.
__
Steve
..

Re: 91 Cherokee blowing ECU fuse
 

"KoRn Kid® (Child of the KoRn)" <korn_kid_forever1@yahoo.com> wrote in
message news:r7i0a1dgstv8rv7jfhvkqg2vpi5mv4kaee@4ax.com...
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.

You didn't tell us whether you tried gooseing the gas...
I'm guessing (gooseing?) that you did, and that it
didn't repeat the performance.

Did the injector wires come close to the secondary
ignition wires? There's a condition called latch-up
where a FET junction can conduct catastrophically
given the right shock... maybe this happened.
Otherwise, just kill a chicken, ------ the blood
around the Jeep on the ground while saying the
appropriate mumbo-jumbo, and take it out for
a test drive, preferably with a cellphone (or ham
radio!) along.

40 amps doesn't normally flow to ground without
making some big holes... frankly, I'm suprised that
the ECU worked after replacing the fuse. Every
input and output in the computer chip is protected
with a diode to ground, and a diode to hot... perhaps
these saved you. Verify that you still get ignition
advance... it might be in limp-along mode.
__
Steve
..

Re: 91 Cherokee blowing ECU fuse
 

You have a dead short some place physically hot likely that tags when
the engine twists under rpm load.

I would be looking at the O2 sensor wires, especially if any are near
the cat and the 4x4 wires that go to the transfer case and cross near
the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

"KoRn Kid® (Child of the KoRn)" wrote:
>
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.
>
> My question.
>
> Are the inputs to the ECC (CPS, etc) protected in any way? or could an
> intermittent short in one of the sensors cause the ECC fuse to blow
> (nightmare). Or is this more than likely a bad injector. The Haynes
> only shows the system in block form and didn't elude to fuses or links
> for the inputs.
>
> Any help would be appreciated as I want to start driving this truck
> again
>
> thanks
>
> -bob-
>
> This E-Mail is certified to be Virus Free by
> Symantic® Norton Anti-Virus Suite

Re: 91 Cherokee blowing ECU fuse
 

You have a dead short some place physically hot likely that tags when
the engine twists under rpm load.

I would be looking at the O2 sensor wires, especially if any are near
the cat and the 4x4 wires that go to the transfer case and cross near
the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

"KoRn Kid® (Child of the KoRn)" wrote:
>
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.
>
> My question.
>
> Are the inputs to the ECC (CPS, etc) protected in any way? or could an
> intermittent short in one of the sensors cause the ECC fuse to blow
> (nightmare). Or is this more than likely a bad injector. The Haynes
> only shows the system in block form and didn't elude to fuses or links
> for the inputs.
>
> Any help would be appreciated as I want to start driving this truck
> again
>
> thanks
>
> -bob-
>
> This E-Mail is certified to be Virus Free by
> Symantic® Norton Anti-Virus Suite

Re: 91 Cherokee blowing ECU fuse
 

You have a dead short some place physically hot likely that tags when
the engine twists under rpm load.

I would be looking at the O2 sensor wires, especially if any are near
the cat and the 4x4 wires that go to the transfer case and cross near
the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

"KoRn Kid® (Child of the KoRn)" wrote:
>
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.
>
> My question.
>
> Are the inputs to the ECC (CPS, etc) protected in any way? or could an
> intermittent short in one of the sensors cause the ECC fuse to blow
> (nightmare). Or is this more than likely a bad injector. The Haynes
> only shows the system in block form and didn't elude to fuses or links
> for the inputs.
>
> Any help would be appreciated as I want to start driving this truck
> again
>
> thanks
>
> -bob-
>
> This E-Mail is certified to be Virus Free by
> Symantic® Norton Anti-Virus Suite

Re: 91 Cherokee blowing ECU fuse
 

You have a dead short some place physically hot likely that tags when
the engine twists under rpm load.

I would be looking at the O2 sensor wires, especially if any are near
the cat and the 4x4 wires that go to the transfer case and cross near
the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

"KoRn Kid® (Child of the KoRn)" wrote:
>
> A week ago I was driving home. I went up a big hill and the truck just
> died and wouldn't restart.
>
> I called a friend who towed me back.
>
> When I checked things out, the ECC fuse (30A in the engine compartment
> fuse block) was blown.
>
> I replaced it and the truck started right up.
>
> I let it run for a few minutes and went to move it up the drive way.
> As soon as I "goosed" the gas, the fuse blew again.
>
> This time I looked more carefully and noticed the plastic square tube
> that carries the wires to the fuel injectors had come off it's mount
> and was lying across the top of the motor.
>
> I inspected it for any wires that might have arced (didn't find any)
> and put it back.
>
> I then replaced the fuse and it started again.
>
> Now until I can figure out what happened, I'm afraid to take it out of
> the driveway.
>
> My question.
>
> Are the inputs to the ECC (CPS, etc) protected in any way? or could an
> intermittent short in one of the sensors cause the ECC fuse to blow
> (nightmare). Or is this more than likely a bad injector. The Haynes
> only shows the system in block form and didn't elude to fuses or links
> for the inputs.
>
> Any help would be appreciated as I want to start driving this truck
> again
>
> thanks
>
> -bob-
>
> This E-Mail is certified to be Virus Free by
> Symantic® Norton Anti-Virus Suite