94 JGC fuel pump
#21
Guest
Posts: n/a
Re: 94 JGC fuel pump
Short answer: bad secondary on ignition coil
Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
Result no start.
Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
ignition system. Decided to throw a new CPS at the problem even though
no diagnosis performed and no error code "11" on the OBD. Picked up
CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
only one 16" extension.
I tested the replacement CPS and it had infinite resistance between B &
C and 5M between C & B as given by link above. The old CPS tested with
infinite resistance between B & C and 3M between C & B. These
resistance measurements are consistent with the behavior of diode
circuit.
Swapped out CPS. Result no start.
Saturday night: crack open the Haynes and load the Popular
Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
years ago for $5. Decide to actually test the basics Sunday morning:
air, fuel and spark.
Air is pretty simple loosen throttle body clamp from air filter box
hose and pop off hose. Fuel is pretty simple remove second quick
connect line on rail, first is pressure regulator. Turn ignition switch
to on with rag covering line. Fuel was flowing so pump is good to go.
Spark is simple use old timing light with induction clamp around spark
wire. Removing plug and shorting out can be hazardous to PCM as wells
as yourself. No spark.
Next test is see if voltage and "pulse" are getting to coil to test PCM
and circuit. Turn to run and there is 12 volts at coil connector. Crank
engine with test light connected between both connections to coil.
Light pulses. So PCM and circuit are good to coil. Spark plug wires
were swapped so they are not suspect. Primary resistance is in
specification 1.2 ohm as given by Haynes. This is easy to test using
the large wiring connector under the battery tray vs. pulling the coil.
Secondary coil test is performed using the large wiring connector and
pulling the coil to distributor lead. This test as 5.8k ohms. Very low
per Haynes specification of 11k to 13k ohms. Call Autozone and they can
test coils. I pull the coil. The 10mm bolts have a free nut on the back
of mounting bracket so you have to use combination wrench as well as
socket to pull it off. I have the counter man test the suspect coil.
The test turns out to be what I just did but I but a $65 CPS serves as
a reminder to measure twice, cut once. Install replacement coil and
engine fires up.
Another recurring problem on the 94 JGC appears to have been fixed,
hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
the diagrams enough to see if the TCM has feedback to the ignition
circuit.
Very good reference to ignition coil resistance by Chip McCoy,
http://groups.google.com/group/rec.a...be3454d?hl=en&
Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
much better. Haynes does not contain diagram of power distribution
center which is necessary for decoding fuse numbers.
Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
Result no start.
Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
ignition system. Decided to throw a new CPS at the problem even though
no diagnosis performed and no error code "11" on the OBD. Picked up
CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
only one 16" extension.
I tested the replacement CPS and it had infinite resistance between B &
C and 5M between C & B as given by link above. The old CPS tested with
infinite resistance between B & C and 3M between C & B. These
resistance measurements are consistent with the behavior of diode
circuit.
Swapped out CPS. Result no start.
Saturday night: crack open the Haynes and load the Popular
Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
years ago for $5. Decide to actually test the basics Sunday morning:
air, fuel and spark.
Air is pretty simple loosen throttle body clamp from air filter box
hose and pop off hose. Fuel is pretty simple remove second quick
connect line on rail, first is pressure regulator. Turn ignition switch
to on with rag covering line. Fuel was flowing so pump is good to go.
Spark is simple use old timing light with induction clamp around spark
wire. Removing plug and shorting out can be hazardous to PCM as wells
as yourself. No spark.
Next test is see if voltage and "pulse" are getting to coil to test PCM
and circuit. Turn to run and there is 12 volts at coil connector. Crank
engine with test light connected between both connections to coil.
Light pulses. So PCM and circuit are good to coil. Spark plug wires
were swapped so they are not suspect. Primary resistance is in
specification 1.2 ohm as given by Haynes. This is easy to test using
the large wiring connector under the battery tray vs. pulling the coil.
Secondary coil test is performed using the large wiring connector and
pulling the coil to distributor lead. This test as 5.8k ohms. Very low
per Haynes specification of 11k to 13k ohms. Call Autozone and they can
test coils. I pull the coil. The 10mm bolts have a free nut on the back
of mounting bracket so you have to use combination wrench as well as
socket to pull it off. I have the counter man test the suspect coil.
The test turns out to be what I just did but I but a $65 CPS serves as
a reminder to measure twice, cut once. Install replacement coil and
engine fires up.
Another recurring problem on the 94 JGC appears to have been fixed,
hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
the diagrams enough to see if the TCM has feedback to the ignition
circuit.
Very good reference to ignition coil resistance by Chip McCoy,
http://groups.google.com/group/rec.a...be3454d?hl=en&
Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
much better. Haynes does not contain diagram of power distribution
center which is necessary for decoding fuse numbers.
#22
Guest
Posts: n/a
Re: 94 JGC fuel pump
It would have taken about two seconds for the guy with the
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
#23
Guest
Posts: n/a
Re: 94 JGC fuel pump
It would have taken about two seconds for the guy with the
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
#24
Guest
Posts: n/a
Re: 94 JGC fuel pump
It would have taken about two seconds for the guy with the
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
#25
Guest
Posts: n/a
Re: 94 JGC fuel pump
It would have taken about two seconds for the guy with the
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
oscilloscope to see the missing secondary winding, the last oscillation
in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Thanks for letting us know what your problem was.
God Bless America, Bill O|||||||O
mailto:--------------------
japeters@mail.com wrote:
>
> Short answer: bad secondary on ignition coil
>
> Long answer: Swapped out spark plugs wires on Thursday morning, $20, at
> Autozone. Existing wires were the OEM Mopar with 12 years and 140k.
> Result no start.
>
> Saturday morning: CPS is critical component of Jeep 6 cylinder 4.0L
> ignition system. Decided to throw a new CPS at the problem even though
> no diagnosis performed and no error code "11" on the OBD. Picked up
> CPS, $68, and a Haynes repair manual JGC 1993 through 2003, $20, at
> Autozone. BTW Autozone cannot test CPS. Forgot about the PITA reaching
> the 11mm bolt. Reference http://members.***.net/wilsond/cps/ . I have
> only one 16" extension.
>
> I tested the replacement CPS and it had infinite resistance between B &
> C and 5M between C & B as given by link above. The old CPS tested with
> infinite resistance between B & C and 3M between C & B. These
> resistance measurements are consistent with the behavior of diode
> circuit.
>
> Swapped out CPS. Result no start.
>
> Saturday night: crack open the Haynes and load the Popular
> Mechanics/Alldata 1994 Jeep CDROM I picked up in Kmart bargain bin 6
> years ago for $5. Decide to actually test the basics Sunday morning:
> air, fuel and spark.
>
> Air is pretty simple loosen throttle body clamp from air filter box
> hose and pop off hose. Fuel is pretty simple remove second quick
> connect line on rail, first is pressure regulator. Turn ignition switch
> to on with rag covering line. Fuel was flowing so pump is good to go.
> Spark is simple use old timing light with induction clamp around spark
> wire. Removing plug and shorting out can be hazardous to PCM as wells
> as yourself. No spark.
>
> Next test is see if voltage and "pulse" are getting to coil to test PCM
> and circuit. Turn to run and there is 12 volts at coil connector. Crank
> engine with test light connected between both connections to coil.
> Light pulses. So PCM and circuit are good to coil. Spark plug wires
> were swapped so they are not suspect. Primary resistance is in
> specification 1.2 ohm as given by Haynes. This is easy to test using
> the large wiring connector under the battery tray vs. pulling the coil.
> Secondary coil test is performed using the large wiring connector and
> pulling the coil to distributor lead. This test as 5.8k ohms. Very low
> per Haynes specification of 11k to 13k ohms. Call Autozone and they can
> test coils. I pull the coil. The 10mm bolts have a free nut on the back
> of mounting bracket so you have to use combination wrench as well as
> socket to pull it off. I have the counter man test the suspect coil.
> The test turns out to be what I just did but I but a $65 CPS serves as
> a reminder to measure twice, cut once. Install replacement coil and
> engine fires up.
>
> Another recurring problem on the 94 JGC appears to have been fixed,
> hard shifts between 2 & 3 on the 42RE when cold. I have not looked at
> the diagrams enough to see if the TCM has feedback to the ignition
> circuit.
>
> Very good reference to ignition coil resistance by Chip McCoy,
> http://groups.google.com/group/rec.a...be3454d?hl=en&
>
> Wiring diagrams in Haynes are pretty good but the Alldata CDROM are
> much better. Haynes does not contain diagram of power distribution
> center which is necessary for decoding fuse numbers.
#26
Guest
Posts: n/a
Re: 94 JGC fuel pump
L.W. ------ III (ßill) wrote:
> It would have taken about two seconds for the guy with the
> oscilloscope to see the missing secondary winding, the last oscillation
> in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Who needs an oscilloscope.
For a Jeep all you need is a rag, test light and ignition key:
Rag to catch gas coming off the fuel line quick connect.
Test light to hook up to the coil connection.
Ignition key to get the OBD codes, if any.
Does not get any simpler than that ;)
#27
Guest
Posts: n/a
Re: 94 JGC fuel pump
L.W. ------ III (ßill) wrote:
> It would have taken about two seconds for the guy with the
> oscilloscope to see the missing secondary winding, the last oscillation
> in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Who needs an oscilloscope.
For a Jeep all you need is a rag, test light and ignition key:
Rag to catch gas coming off the fuel line quick connect.
Test light to hook up to the coil connection.
Ignition key to get the OBD codes, if any.
Does not get any simpler than that ;)
#28
Guest
Posts: n/a
Re: 94 JGC fuel pump
L.W. ------ III (ßill) wrote:
> It would have taken about two seconds for the guy with the
> oscilloscope to see the missing secondary winding, the last oscillation
> in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Who needs an oscilloscope.
For a Jeep all you need is a rag, test light and ignition key:
Rag to catch gas coming off the fuel line quick connect.
Test light to hook up to the coil connection.
Ignition key to get the OBD codes, if any.
Does not get any simpler than that ;)
#29
Guest
Posts: n/a
Re: 94 JGC fuel pump
L.W. ------ III (ßill) wrote:
> It would have taken about two seconds for the guy with the
> oscilloscope to see the missing secondary winding, the last oscillation
> in this picture: http://www.----------.com/oscilloscopeIgnitionTest.jpg
Who needs an oscilloscope.
For a Jeep all you need is a rag, test light and ignition key:
Rag to catch gas coming off the fuel line quick connect.
Test light to hook up to the coil connection.
Ignition key to get the OBD codes, if any.
Does not get any simpler than that ;)
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