1990 xj long crank time and hard starting
10-19-2011, 06:56 AM
#61
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
The closer it sets to the flywheel the stronger the signal. We did it at the dealership before they came out with the TSB on running the CPS wires directly to the ECU. Just took the first drill bit that wouldn't slide through the holes and drilled 'em out. Upon installation, we made sure to push down on the CPS as tightening the bolts.
What AC voltage are you getting from the CPS while cranking? Let's start with that. That voltage reading gives us a starting point and we can gauge the improvement should you need to drill.
10-19-2011, 06:47 PM
#62
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
Yes. I've done it with positive results more times than I can remember. The procedure was suggested to us by the service engineers at Jeep.
The closer it sets to the flywheel the stronger the signal. We did it at the dealership before they came out with the TSB on running the CPS wires directly to the ECU. Just took the first drill bit that wouldn't slide through the holes and drilled 'em out. Upon installation, we made sure to push down on the CPS as tightening the bolts.
What AC voltage are you getting from the CPS while cranking? Let's start with that. That voltage reading gives us a starting point and we can gauge the improvement should you need to drill.
The closer it sets to the flywheel the stronger the signal. We did it at the dealership before they came out with the TSB on running the CPS wires directly to the ECU. Just took the first drill bit that wouldn't slide through the holes and drilled 'em out. Upon installation, we made sure to push down on the CPS as tightening the bolts.
What AC voltage are you getting from the CPS while cranking? Let's start with that. That voltage reading gives us a starting point and we can gauge the improvement should you need to drill.
10-19-2011, 06:49 PM
#63
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
AC voltage.
10-19-2011, 07:00 PM
#64
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
so i put the meter on on ACV 200 with the key on reading .2 while cranking it jumped up to 7.8?
ps. i have the same meter as DFlinstone as he pictured
ps. i have the same meter as DFlinstone as he pictured
10-19-2011, 07:17 PM
#65
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CPS disconnected from harness and probing the CPS plug itself, right?
10-19-2011, 07:23 PM
#66
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
10-19-2011, 07:25 PM
#67
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Don't leave it plugged in. You want to read the AC voltage signal the CPS is putting out ONLY.
10-19-2011, 08:01 PM
#68
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
10-19-2011, 08:06 PM
#69
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Good find. Remember you want .5 AC volts. If you have a manual trans, take this opportunity to wipe any worn off clutch material from the CPS tip. That material can reduce teh signal of the CPS significantly.
10-19-2011, 08:08 PM
#71
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Starting any quicker?
10-19-2011, 09:46 PM
#72
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
it cranks a few times then starts but the cps is still reading .3 but it started up and drove got to the gas station and it died. Could have been i was on the gas light and made a hard left. so do you think i should wallow out the holes on the cps or get another one because this one might be defective?
10-19-2011, 10:01 PM
#73
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,875
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Wallow it and see what you get for a reading. Do this in the name of sound automotive experimentation and diagnostics. It could benefit the Jeep community as a whole. LOL
10-19-2011, 10:18 PM
#74
Member
Thread Starter
Join Date: Oct 2011
Location: California
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
i guess it couldn't hurt except returning it would probably be out of the question. thank im gonna try this out tomorrow and post my findings lol
10-19-2011, 10:57 PM
#75
Senior Member
Join Date: May 2011
Location: Flagstaff, Arizona
Posts: 609
Likes: 0
Received 2 Likes
on
2 Posts
Year: 1998
Model: Cherokee
Engine: 4.0L I6
Check fuel line, priming it by turning it on (without cranking) and off again a few times, then cranking always works for mine