Weird starting issue (plus gauges) - JeepForum.com

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post #1 of 33 Old 06-18-2017, 11:19 AM Thread Starter
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Weird starting issue (plus gauges)

Where to start.
Yesterday turned over fine but wouldn't start. All of a sudden it started and I was able to take it for a spin for about half an hour. Drove home and parked it.
Went today to take it out again and it did the spinning thing but no start.
The Relays are good as I swapped them around. I can hear a buzzing from the gas tank which I am pretty sure is the pump (Pump was replaced 3 years ago with a Bosch unit). Disconnected and reconnected the Camshaft Position Sensor and Oil Pressure Sensor (since I was there) and now it doesn't even spin without bypassing the starter relay.

Another symptom is the gas and power gauges stay at zero. Other lights work fine and the gauges work in the actuator test

I have mentioned before that I have had with rare intermittent issues with starting (I was able to work around it by putting it into run, and bypassing the Starter relay) and I am wondering if it has finally come to a head.


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post #2 of 33 Old 06-18-2017, 11:45 AM Thread Starter
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I am planning on pulling ignition apart, maybe it is a two parter where the switch pin just flaked out but it still doesn't explain why it doesn't start when the engine does turn over and why the fuel and voltage gauges are zero

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post #3 of 33 Old 06-18-2017, 12:00 PM Thread Starter
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I also came across this thread
http://www.jeepforum.com/forum/f9/19...orking-746647/
When they say CPS, is that the Crank or Cam?

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post #4 of 33 Old 06-18-2017, 12:04 PM
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When the gauges don’t respond usually either you have no power to the PCM or power but no 5v from the 5v output at the PCM. Most, if not all I have seen are ‘97s but still check fuses 11 in the fuse block & 6 in the PDC with a meter. If good go to the black (C-2) connector at the PCM & check pins a-2 & a22 for 12v power & with it plugged in check pin a17 for 5v.

This does not address the no crank, so insert a fuse in slot 20 of the fuse block to bypass the clutch switch. If nothing, removing the ignition switch to check the actuator pin would be next & if good turn the switch with a screwdriver to see if it will engage the starter.
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post #5 of 33 Old 06-18-2017, 01:04 PM Thread Starter
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11 and 6 have continuity.
Ignition pin is good (I had already pulled it)
All off
Pin 2 0v
Pin 22 12v

Run
Pin 2 12v
Pin 22 12v

How do you check pin 17 for 5v if it is plugged In? Is there a different spot down the corresponding wire I can check based on?

Also wouldn't the actuator test negate this test?

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post #6 of 33 Old 06-18-2017, 02:01 PM Thread Starter
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Dumb thought,
ignore

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post #7 of 33 Old 06-18-2017, 02:49 PM Thread Starter
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Basically as it stands right now
Cranks over but won't start
Voltage and fuel gauge are at zero even though there is about a half a tank and newish battery.

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post #8 of 33 Old 06-18-2017, 03:08 PM
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You have to “back probe” it. Try getting a thin wire or the like to get between the connector plastic & the terminal. It is tight. You can also follow that wire to one of the sensors like the crank or cam sensors & check there (unplugged). You can penetrate the insulation on that wire but is not recommended as it allows corrosion to get in.

There is also a 5v supply in the white connector at pin b31 & so far every one that loses one loses both but can be checked the same way. You might be able to check that pin at the PCM with the connector unplugged & the black one plugged in but I’m not sure & don’t want you chasing the wrong thing.

If turning the ignition switch with the fuse in slot 20 (manual trans) does not get it to engage the starter but jumping the relay does you may have a bad switch which can be tested if needed.
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post #9 of 33 Old 06-18-2017, 05:32 PM Thread Starter
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Quote:
Originally Posted by Rubi4MyMrs View Post
You have to “back probe” it. Try getting a thin wire or the like to get between the connector plastic & the terminal. It is tight. You can also follow that wire to one of the sensors like the crank or cam sensors & check there (unplugged). You can penetrate the insulation on that wire but is not recommended as it allows corrosion to get in.

There is also a 5v supply in the white connector at pin b31 & so far every one that loses one loses both but can be checked the same way. You might be able to check that pin at the PCM with the connector unplugged & the black one plugged in but I’m not sure & don’t want you chasing the wrong thing.

If turning the ignition switch with the fuse in slot 20 (manual trans) does not get it to engage the starter but jumping the relay does you may have a bad switch which can be tested if needed.
Thanks will try it out!
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post #10 of 33 Old 06-19-2017, 05:14 AM Thread Starter
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Came across this thread
http://www.jeepforum.com/forum/f11/c...-maybe-889010/

Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.


Could it be that simple?

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post #11 of 33 Old 06-19-2017, 10:03 AM
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It may be.

I skimmed through that link…

Missing in those tests appears to be the fact that you need 5v to the sensor as well as some other sensors. Start there. If you do have the full 5v you can move on to testing sensors, etc.


There are 4 basic problems that seem to happen most often with crank but no start. Fuse 11 gets blown or the ignition switch is not sending power to that fuse, the crank sensor goes bad, the PCM loses its 5v outputs or the PCM won’t ground the ASD & FP relay coils. There can be other reasons (some also noted below) but I see these 4 most often. In the links below, badKrma lost the relay grounds from the PCM & the relays would not close so he was able to jump the relays to get it going. Ifixyawata was not getting 5v output from the PCM & added an external power source to get his going. Both are workarounds for bad PCMs. Obviously fuses & sensors are easier fixes.

In the cases of the bad PCMs both started out with what seemed like the same problem but the process lead to differences which eventually identified the underlying issue. Both were bad PCMs but are now on the road.


badKrma
http://www.wranglerforum.com/f210/no...l#post10742890

Ifixyawata
http://www.wranglerforum.com/f210/no...l#post11636018


Then there is this with low voltage at the 5v pins

5v supply to speed sensor shorted causing low voltage to all sensors. Not found until about post 35

http://www.jeepforum.com/forum/f9/ne...l#post38075434

There are also cases where the capacitors in the PCMs leak & some have replaced them & not had to replace the PCM. 2 cases here…

http://www.jeepforum.com/forum/f9/19...rting-2901058/

Even this…

Corrosion at PCM connector

http://www.wranglerforum.com/f210/no...l#post30002297

You see there can be several causes; it is just a process to finding the problem.
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post #12 of 33 Old 06-19-2017, 12:06 PM Thread Starter
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Quote:
Originally Posted by Rubi4MyMrs View Post
It may be.

I skimmed through that link…

Missing in those tests appears to be the fact that you need 5v to the sensor as well as some other sensors. Start there. If you do have the full 5v you can move on to testing sensors, etc.


There are 4 basic problems that seem to happen most often with crank but no start. Fuse 11 gets blown or the ignition switch is not sending power to that fuse, the crank sensor goes bad, the PCM loses its 5v outputs or the PCM won’t ground the ASD & FP relay coils. There can be other reasons (some also noted below) but I see these 4 most often. In the links below, badKrma lost the relay grounds from the PCM & the relays would not close so he was able to jump the relays to get it going. Ifixyawata was not getting 5v output from the PCM & added an external power source to get his going. Both are workarounds for bad PCMs. Obviously fuses & sensors are easier fixes.

In the cases of the bad PCMs both started out with what seemed like the same problem but the process lead to differences which eventually identified the underlying issue. Both were bad PCMs but are now on the road.


badKrma
http://www.wranglerforum.com/f210/no...l#post10742890

Ifixyawata
http://www.wranglerforum.com/f210/no...l#post11636018


Then there is this with low voltage at the 5v pins

5v supply to speed sensor shorted causing low voltage to all sensors. Not found until about post 35

http://www.jeepforum.com/forum/f9/ne...l#post38075434

There are also cases where the capacitors in the PCMs leak & some have replaced them & not had to replace the PCM. 2 cases here…

http://www.jeepforum.com/forum/f9/19...rting-2901058/

Even this…

Corrosion at PCM connector

http://www.wranglerforum.com/f210/no...l#post30002297

You see there can be several causes; it is just a process to finding the problem.
Sounds good. I am going to try to see if I get the +5V on the other connector first if I do then I might try to see about getting into the black connector and probing it but tight is an understatement you can't even see any of the wires going into the connector.
Will have some more reading material tonight I see.

That all said though, by doing the actuator test and the gauges jump wouldnt that confirm the +5V is working?

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post #13 of 33 Old 06-19-2017, 01:39 PM Thread Starter
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Measured pin 17. Wasn't sure what you meant how to get it then realized when I actually looked at it the connector breaks in two. For anyone later on. This is how you get it, it's the orange wire on the second row.
Got 5 v
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post #14 of 33 Old 06-19-2017, 01:50 PM Thread Starter
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Disconnected Crankshaft sensor. Gauges started working
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post #15 of 33 Old 06-19-2017, 04:07 PM
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Progress!



Probably just the link above where the speed sensor (wiring) was shorted. The sensor or the wiring from it (sensor or ground wires) may be draining the 5v from the PCM causing none of the sensors to send data & the cluster gauges not to read. It may be a shorted sensor, easy to check, or one of the 2 wires other than the 5v one may be shorted to ground. Also easy to check. If it was in the 5v wire, disconnecting the sensor would not get the rest of the circuit working.

Did you get it to engage the starter with the key?
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