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Unread 07-11-2013, 10:36 AM   #31
Uniblurb
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Quote:
Originally Posted by dellis View Post
For example, I commonly see direction to replace the Crankshaft Sensor to solve a random stall problem ... and the owner does this only to discover that their problem continues to exist. But, if the owner had simply tested the output of their ASD relay during a stall/no-start, and they saw +12V, then they would know that the Crankshaft Sensor is not their problem. Why? Because the PCM will not activate the ASD relay unless it has a Crankshaft Sensor signal.
Well dellis, I'm probably somewhat guilty of of pushing the crank sensor as the stall/no-start problems but I'm on my 4th one (2 junk aftermarket crank sensors included). But I normally post the CKP testing diagram beforehand and don't tell users to just go out and buy a new pricey Mopar crank sensor unless it tests bad.

I'd be interested in how you test the voltage on the ASD relay output, including where exactly to place your meter probes, and do you do this with the relay removed/engine cranking over? Or maybe just with the key on? Thanks!

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96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 07-11-2013, 10:44 AM   #32
dellis
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Quote:
Originally Posted by Uniblurb View Post
Well dellis, I'm probably somewhat guilty of of pushing the crank sensor as the stall/no-start problems but I'm on my 4th one (2 junk aftermarket crank sensors included). But I normally post the CKP testing diagram beforehand and don't tell users to just go out and buy a new pricey Mopar crank sensor unless it tests bad.
Yes, I've always noted that you provide good diagnostic direction with those sensors. Of course, if it is testing bad, then it should be replaced.

Quote:
Originally Posted by Uniblurb View Post
I'd be interested in how you test the voltage on the ASD relay output, including where exactly to place your meter probes, and do you do this with the relay removed/engine cranking over? Or maybe just with the key on? Thanks!
There are two ways that I have done it, and both are with the engine cranking (because I'm interested in the ASD relay's behavior during a no-start). Of course, the PCM will activate the ASD for a couple of seconds when you first put the key-on, but I am pretty sure it turns off if cranking doesn't start. Regardless, once cranking begins, if the PCM doesn't see a proper signal from the Crankshaft Position Sensor, then the ASD is shut off.

(1) Put a noid light on a fuel injector. The noid light will only pulse if the ASD is engaged.
(2) I realize that not everyone has a noid light, so there is also this simple test that can be done with a voltmeter. Back-probe the 12V line of a fuel injector connector, and measure the voltage to any ground. I back-probe by inserting a sewing needle into the back of the connector. This could also be done at the coil (if you suspect the coil is losing its 12V signal), but the fuel injectors are easier to access.

By testing the circuit all the way out to the injectors, I am not only including the possibility of the PCM not engaging the ASD, but also checking on the possibility of (a) bad ASD relay, (b) bad wiring from ASD to injectors/coil, and (c) corrosion at the PDC.
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Unread 07-11-2013, 11:05 AM   #33
Uniblurb
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Quote:
Originally Posted by dellis View Post
Yes, I've always noted that you provide good diagnostic direction with those sensors. Of course, if it is testing bad, then it should be replaced.


There are two ways that I have done it, and both are with the engine cranking (because I'm interested in the ASD relay's behavior during a no-start).

(1) Put a noid light on a fuel injector. The noid light will only pulse if the ASD is engaged.
(2) I realize that not everyone has a noid light, so there is also this simple test that can be done with a voltmeter. Back-probe the 12V line of a fuel injector connector, and measure the voltage to any ground. I back-probe by inserting a sewing needle into the back of the connector. This could also be done at the coil (if you suspect the coil is losing its 12V signal), but the fuel injectors are easier to access.
Thanks, and I've found if you switch your multimeter probes on the crank sensor connector itself, instead of black on the middle B pin (ground cavity) and red on the C pin (power), it will give you a false reading. Not sure if it has to do with the magnet but you may find resistance when the senor is good if testing with red probe on B (ground) and black probe on C (power).

I was thinking about getting a noid light, they aren't very expensive, but the only ones I've seen are for testing the spark plug/coil wires.

If you're testing the voltage at the fuel injector connector, and there is none, couldn't this just also point to you having a bad relay or crank sensor? I thought maybe the test was at the PDC ADS relay female receptacles? Thanks!
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 07-11-2013, 11:31 AM   #34
dellis
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Quote:
Originally Posted by Uniblurb View Post
If you're testing the voltage at the fuel injector connector, and there is none, couldn't this just also point to you having a bad relay or crank sensor? I thought maybe the test was at the PDC ADS relay female receptacles? Thanks!
Yep, it can be a lot of things. My direction above is a divide and conquer strategy for attempting to isolate the cause. The reason that I think this test is one of the first to do, is because it verifies a number of crucial no-start and stall problems. Look at all the things that have to be good for there to be 12V at the injector:

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Unread 07-11-2013, 11:42 AM   #35
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Yep, it can be a lot of things. My direction above is a divide and conquer strategy for attempting to isolate the cause. The reason that I think this test is one of the first to do, is because it verifies a number of crucial no-start and stall problems. Look at all the things that have to be good for there to be 12V at the injector:

Ok, thanks for the info dellis!
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 07-11-2013, 11:52 AM   #36
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By the way, I changed the graphic a little around the PCM so that it is not so authoritative about the PCM's integrity. There are PCM problems that can exist even if the injectors are powered (e.g., the coil driver is getting whacky).

Updating my thoughts here .... if a Jeep has power properly going to all injectors (best tested with a noid light), then this eliminates all problems with the PCM except the PCM's coil driver as a cause of stalling or no starts. In other words, all the crucial functions of the PCM need to be operating properly in order for the injectors to fire. (This includes bad connections and wires, bad power, and core sensor operations.)

Can anyone think of an exception? I can't off the top of my head ...

Of course, the PCM's coil driver is quite another animal with its own set of odd behavior. And, if it is a coil driver problem and you replace a PCM without addressing what caused your coil driver to fail (typically the coil), then ... like blowing a fuse again ... you could destroy the coil driver in your replacement PCM.
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Unread 07-11-2013, 07:09 PM   #37
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In other words, all the crucial functions of the PCM need to be operating properly in order for the injectors to fire. (This includes bad connections and wires, bad power, and core sensor operations.)
ASD relay ground logic:
  • switch on (for 1 - 3 seconds)
  • cranking (with exception of no crank sensor signal for three seconds)
  • running - If the PCM senses the crank signal has stopped, it will remove the ground
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Unread 07-12-2013, 06:48 PM   #38
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Thanks for the new info. I will put it to use this weekend and see if I can find anything. Just a side note over the last two days of driving I have discovered a few things. The stalling mainly occurs when my gas is at a 1/4 tank or lower. Also if going up an incline with this amount of gas is when it seems to happen. If I try to restart under these conditions it wont. If I let the Jeep roll until it is facing downward with these conditions it starts. I had 3 stalls in a mile trip today all while going up a modest incline with 1/4 or less in gas. Wouldn't restart until I had it facing downhill then would restart. I stopped and put enough gas into it to give it a 1/2 tank. Did fine under all conditions after gas. Is there something maybe with the tank or pump pulling from it at certain levels or angles ?
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Unread 07-12-2013, 06:54 PM   #39
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Sorry man, i couldn't control myself

sounds like you need a sending unit, but check the connector back by the fuel pump
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Unread 07-12-2013, 07:02 PM   #40
dellis
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I think you are coming full circle to addressing the problem that was under consideration a month ago when you whacked the tank and it sprung to life ... you have a fuel system problem. But, again, you want to test it during a stalling or no-start condition.

Without testing the pressure, ZeeJay is likely correct - you need to replace your fuel pump assembly. There's also a chance you have some water in your tank ...
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Unread 07-12-2013, 07:12 PM   #41
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check here to see if you vehicle has a recall that hasnt been performed.
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Unread 07-13-2013, 08:32 AM   #42
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What zee said
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Unread 07-13-2013, 02:48 PM   #43
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Originally Posted by Uniblurb View Post
He's installed a new battery and reman PCM as far as I can tell Zee..

http://www.jeepforum.com/forum/f13/n...l#post15533364

Reynoldsjp, here's a similar scenario I went through with my 96 4.0. Couldn't figure out my stall/no-start problems and took it to the dealer when I didn't know any better. They replaced the PCM along with installing a new crank sensor. Used one of those high-quality reman PCM's out of Miami (ACR-All Computer Resources, sic). Ran good but in less than a year had the same old stall/no-start problems and it fried another PCM. Turns out the mechanic/dealer didn't clean the engine ground by the coil stud which grounds the PCM which is the reason it fried 2 PCM's. It should also be noted most all sensors are grounded through the PCM so if this engine ground is bad you're going to have problems. Thanks to ZeeJay for diagnosing this engine/PCM grounding problem!

I didn't trust the dealer anymore so contacted ACR directly and got another reman PCM under warranty. And this "lifetime warranty" only covers 1 free replacement PCM. Nice! Installed the PCM, after cleaning off the 3 engine grounds & body grounds, and believe I may have had to replace another OE/Mopar crank sensor too.

So check for codes but also clean off all your grounds! Also check your crank sensor using the below test (5.2 & 4.0) with a multimeter set to the lowest ohm setting. On the disconnected connector to the sensor itself place the black probe on the middle "B" pin (ground cavity) and red probe on the "C" pin (power). Any resistance at all and you have a bad sensor. Only go with a Mopar sensor if bad our you'll be sorry. Good luck!
Dont forget to clean the ground thats around the lower passenger side rear on the block, theres a ground strap there. Mine is caked in grunge ! I will clean it perhaps tomorrow when i do the CPS.
Something i found while ago is all the mounting bolts to my PCM were loose, would have that effected anything ? Are those mounting bolts perhaps part of the ground to pcm ?
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Unread 07-13-2013, 05:01 PM   #44
reynoldsjp
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ok so i'm back to a no start status and check engine light is on. I rented a code reader and got three codes. PO 113, PO 320 , P1388. I am looking these up now if anyone can give me info much appreciated
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Unread 07-13-2013, 05:11 PM   #45
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P0113 - Intake Air Temperature Sensor Voltage High

P0320 - No Crank Reference Signal at PCM This will cause a no-start situation. Your crankshaft position sensor is either defective, the wiring to it is defective, it is not receiving proper voltage, or the connection at the PCM is defective. Uniblurb has already provided a test for the CKPS earlier in this thread.

P1388 - Faulty ASD Relay. This will also cause a no-start condition ... the relay itself can be switched with something like the horn relay to see if that is the problem. It could also have corrosion at the terminals, the fuse to it could be blown, or it could have faulty wiring. But, if this is the source of your problem, switching the two relays will solve it most of the time.
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