Jeep Cherokee hard starts (CPS?)
 

Hi all -

I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
auto-transmission. I have been fighting a hard starting problem as
follows. In the morning from a cold start it will take up to 10
seconds to start. And then it will run very rough until it warms a
bit. Subsequent restarts then take less than 2 seconds, and I don't
even need to step on the gas. When it starts hard, I have tried the
trick of turning the key on and off a few times to let the fuel
pressure come up. This seems to make it worse, if anything. I have
replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
PCV valve on this model). There is no leaking around the injectors,
pressure regulator or fuel lines that I can see.

>From everything I've read on this group and elsewhere, the next likely
candidate is the CPS. I've read that this gadget is not easy to get
at. So, my question is, is this something that a DIY'er can tackle
without screwing things up? Where exactly is it located? Do I need
anything other than basic handtools to get it out and get a new one in?
Any other words of advice?

Thanks for all your help,
Bud

Re: Jeep Cherokee hard starts (CPS?)
 

You are describing a dirty connection on the TPS or throttle position
sensor. The best cleaner is electronic contact cleaner but WD40 will
work in a pinch.

The sensor is on the throttle body. Both plugs and sockets there can
benefit from a clean.

And if the 91 still has the renix computer system they all seem to take
a while to start first time in the day, but they run smooth still....

The CPS plug and socket also fail from bad connections, but that usually
causes a stall. While you have the contact cleaner out, that plug can
use it too. The CPS is on the bell housing top drivers side. Follow
the wires for it's plug, most are on the top of the intake manifold.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

You are describing a dirty connection on the TPS or throttle position
sensor. The best cleaner is electronic contact cleaner but WD40 will
work in a pinch.

The sensor is on the throttle body. Both plugs and sockets there can
benefit from a clean.

And if the 91 still has the renix computer system they all seem to take
a while to start first time in the day, but they run smooth still....

The CPS plug and socket also fail from bad connections, but that usually
causes a stall. While you have the contact cleaner out, that plug can
use it too. The CPS is on the bell housing top drivers side. Follow
the wires for it's plug, most are on the top of the intake manifold.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

You are describing a dirty connection on the TPS or throttle position
sensor. The best cleaner is electronic contact cleaner but WD40 will
work in a pinch.

The sensor is on the throttle body. Both plugs and sockets there can
benefit from a clean.

And if the 91 still has the renix computer system they all seem to take
a while to start first time in the day, but they run smooth still....

The CPS plug and socket also fail from bad connections, but that usually
causes a stall. While you have the contact cleaner out, that plug can
use it too. The CPS is on the bell housing top drivers side. Follow
the wires for it's plug, most are on the top of the intake manifold.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

You are describing a dirty connection on the TPS or throttle position
sensor. The best cleaner is electronic contact cleaner but WD40 will
work in a pinch.

The sensor is on the throttle body. Both plugs and sockets there can
benefit from a clean.

And if the 91 still has the renix computer system they all seem to take
a while to start first time in the day, but they run smooth still....

The CPS plug and socket also fail from bad connections, but that usually
causes a stall. While you have the contact cleaner out, that plug can
use it too. The CPS is on the bell housing top drivers side. Follow
the wires for it's plug, most are on the top of the intake manifold.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

Hi Bud,
Can you hear your pump run for two seconds, every time you cycle
the ignition switch? If not you need a new pump and/or relay. The pump
will not shut off on pressure, it by-passes.
The symptoms of a Crankcase Position Sensor are it won't start at
all, shuts off while driving normally down the road, and won't restart
for a few minutes, defaults to safe mode with a top speed of twenty
miles an hour. will not start unless the CPS has been disconnected and
reconnected.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

Hi Bud,
Can you hear your pump run for two seconds, every time you cycle
the ignition switch? If not you need a new pump and/or relay. The pump
will not shut off on pressure, it by-passes.
The symptoms of a Crankcase Position Sensor are it won't start at
all, shuts off while driving normally down the road, and won't restart
for a few minutes, defaults to safe mode with a top speed of twenty
miles an hour. will not start unless the CPS has been disconnected and
reconnected.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

Hi Bud,
Can you hear your pump run for two seconds, every time you cycle
the ignition switch? If not you need a new pump and/or relay. The pump
will not shut off on pressure, it by-passes.
The symptoms of a Crankcase Position Sensor are it won't start at
all, shuts off while driving normally down the road, and won't restart
for a few minutes, defaults to safe mode with a top speed of twenty
miles an hour. will not start unless the CPS has been disconnected and
reconnected.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud

Re: Jeep Cherokee hard starts (CPS?)
 

Hi Bud,
Can you hear your pump run for two seconds, every time you cycle
the ignition switch? If not you need a new pump and/or relay. The pump
will not shut off on pressure, it by-passes.
The symptoms of a Crankcase Position Sensor are it won't start at
all, shuts off while driving normally down the road, and won't restart
for a few minutes, defaults to safe mode with a top speed of twenty
miles an hour. will not start unless the CPS has been disconnected and
reconnected.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

Bud wrote:
>
> Hi all -
>
> I have a 1991 Jeep Cherokee Laredo with the in-line 6 and
> auto-transmission. I have been fighting a hard starting problem as
> follows. In the morning from a cold start it will take up to 10
> seconds to start. And then it will run very rough until it warms a
> bit. Subsequent restarts then take less than 2 seconds, and I don't
> even need to step on the gas. When it starts hard, I have tried the
> trick of turning the key on and off a few times to let the fuel
> pressure come up. This seems to make it worse, if anything. I have
> replaced the plugs, wires, rotor, cap, air filter and CCV tubing (no
> PCV valve on this model). There is no leaking around the injectors,
> pressure regulator or fuel lines that I can see.
>
> >From everything I've read on this group and elsewhere, the next likely
> candidate is the CPS. I've read that this gadget is not easy to get
> at. So, my question is, is this something that a DIY'er can tackle
> without screwing things up? Where exactly is it located? Do I need
> anything other than basic handtools to get it out and get a new one in?
> Any other words of advice?
>
> Thanks for all your help,
> Bud