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Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 24399
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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I have a 97 jeep wrangler with no spark. Fuel pump cycles

Customer Question

I have a 97 jeep wrangler with no spark. Fuel pump cycles when key is turn on.
Replaced Crank sensor coil pick up coil in dist. Replaced all the relays but no power to the coil. What am I missing ?
Submitted: 1 year ago.
Category: Jeep
Expert:  Dan replied 1 year ago.

Hello, my name is***** the check engine light come on for bulb test? Are you setting any codes? Thanks.

Customer: replied 1 year ago.
No Codes and Yes CEL comes on
Expert:  Dan replied 1 year ago.

Do you have scan tool to monitor cam sensor and crank sensor signal? The PCM requires crank signal to enable main relay which sends power to coil. The cam/crank sensors use the same 5v circuit so if cam sensor is acting up it can cause crank signal to have problems.

Customer: replied 1 year ago.
I replaced both of them with new ones
Expert:  Dan replied 1 year ago.

Sometimes aftermarket sensors can cause problems if you didn't buy from Jeep. Next step is to check wiring. Check the voltage on the orange wire at the Camshaft Position (CMP) sensor. If voltage is less than 7 volts, unplug the Crankshaft Position (CKP) sensor, cycle the key off and on again and recheck. If the voltage is now at least 7 volts, reconnect the CKP sensor. If the voltage goes down again, the CKP sensor is shorted. The Vehicle Speed Sensor (VSS) could also be shorting out the 8 volt power supply. If 8v is good then next step is checking wiring between cam/crank sensors and PCM, each wire should have under 5 ohms resistance, if good replace the PCM. Brown/yellow wires get ground from PCM and signal wires send 0-5v square wav to PCM. If wiring tests good and sensors are sending good signal then replace PCM. Here is a wire diagram to help with testing, let me know if there is anything else I can do to help. Thanks.
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https://www.dropbox.com/s/qt0hc5z2vkmlxzh/ck.png?dl=0
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Customer: replied 1 year ago.
Okay I will try that. Shouldn't I be getting 12v at coil from the ASD relay ? No matter if sensors are bad ?
Expert:  Dan replied 1 year ago.

The ASD relay only activates when PCM see's crank signal. I'm assuming ASD relay is not activating. Let me know, thanks.

Expert:  Dan replied 1 year ago.

If you remove relay, jump pin 87 to pin 30 that should force voltage to coil which will at least prove that part of wiring is good. Let me know, thanks.

Customer: replied 1 year ago.
Can you forward a link for the wiring dia in the ignition system and the ASD relay ? Thanks
Customer: replied 1 year ago.
Ok I tested all orange wires CPK CPS TPS VSS all have 5.13v. I replaced CPK with one from donor jeep that I know is good
Still no Spark or 12v at coil. I jumper ASD relay get 12v when I do that. Checked wiring from CPK to PCM . All Good
Also check and cleaned all grounds . There is one weird thing on the ASD relay I get 12v at one terminal but the other shows 11.56v but wont turn on test light ? Shows voltage with meter but not with test light . I also tried changing PCM with donor jeep but its a 2001 with coil packs and didn't work . Didn't think it would. I'm out of ideas . Please help Thanks
Expert:  Dan replied 1 year ago.

What pin # *****'t light up test light? That would point toward poor connection.

Customer: replied 1 year ago.
84 on ASD relay
Expert:  Dan replied 1 year ago.

One pin should have power only with key on and one pin should have power at all times. Which one of the two is having the testlight problem.?

Customer: replied 1 year ago.
the one with power with key on
Expert:  Dan replied 1 year ago.

Unplug PCM and ground dark blue/yellow wire at pin C3 with key on. This should activate the ASD relay putting power at coil, if so it sounds like your PCM has failed. let m know how it goes, thanks.

Customer: replied 1 year ago.
Ok I hear asd relay clicking but no power to coil
Expert:  Dan replied 1 year ago.

Replace the ASD relay if you haven't already and let me know if that helps

Customer: replied 1 year ago.
Done still nothing
Expert:  Dan replied 1 year ago.

Ok, lets try and figure out why the test light won't light. This gets power from 10 amp fuse 11 on interior. Check to see if test light will turn on when touching fuse with key on.

Customer: replied 1 year ago.
its the terminal with power all the time that shows 11.59 v but shows nothing with light
Expert:  Dan replied 1 year ago.

Fuse gets power from ignition switch via dark blue wire. Next step is accessing wire at ignition switch to see if it can turn light on. Let me know, thanks.

Customer: replied 1 year ago.
Okay I jumpered the terminal 12v hot all the time on asd relay to battery and it starts
What feeds that terminal.
Expert:  Dan replied 1 year ago.

The ignition switch feeds the fuse which feeds the relay. That is why I was having you do test at ignition switch so we could se where problem was and repair.

Customer: replied 1 year ago.
Buts its hot all the time not switched. The other terminal is 12v switched
Expert:  Dan replied 1 year ago.

Does vehicle start when jumping pin 87 to pin 30?

Expert:  Dan replied 1 year ago.

Remove/reinsert fuse 3 under hood which is a 30 amp incase it has a bad connection. Let me know, thanks.

Customer: replied 1 year ago.
I replaced ignition switch before all this thinking it may be it . Ok so what I know is if I put 12v from battery to 12v hot all the time on ASD relay it starts and runs . So it seems to be from the hot all time terminal to fuse ? Where does that get power from ?
Expert:  Amedee replied 1 year ago.

Hello! Different expert here. Did you still need help? If so, please accept my offer and call me so we can talk over the phone.

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