CPS Replaced, No Spark Still......

So disconnect all the Throttle body sensors, as well as the cam sensor? Then leave the rest connected and see if I can start it?? Im not worried about the idle, I want to know that I am getting spark, but I will check the O2 Sensor and make sure that none of the wires are shorted. Then I will try and see if disconnecting the TPS, and IAC and Cam sensors will get it to run. Thanks for the ideas. I'll keep trying. Plus I will be finishing testing of the coil and see what I come up with.

Jeff
 
This Jeep doesn't have one. Its a '94. I looked all over for one, and some in the JY have them, I know what they are, but this one doesn't have one.

Next....

Jeff
 
Coil didn't test within specs, so I am gonna replace it for right now, but I will be using a less expensive replacement as I am going to be upgrading to the Screamin Demon coil, wires, cap and rotor, as well as put on a cold air intake setup so that I can replace the current factory setup with a better/more efficient one. I am going to try the grounds, but again I was getting continuity in the ASD relay when the ignition was on, and none when the ignition was off. but I am wondering if there is something else I am missing in relation to what's after the ASD relay. Keep suggestions/ideas coming.

Jeff
 
ihscoutlover said:
Ok got the CPS changed out on Saturday(after not getting the correct part from the stealership). Set it up, still cranking but no spark. Also no pressurization of the fuel rail. I'm starting to go bald with some of the hairs being pulled out. Cam sensor/pickup coil next, or coil?? I will be checking the dealership part to verify its good, but from reading on here the OEM parts seem to see less failure than the Chain Store parts do. Thoughts on where to proceed next? And yes I reclaimed my membership again, finally after about 3-4 years of non-existance.

Jeff
Click to expand...

If you have "Set it up, still cranking but no spark. Also no pressurization of the fuel rail", then you are probably barking up the wrong trees!!!!

Look for something that is keeping the fuel pump from even priming before cranking, no fuel and no spark means something back in the ECU/PCM is not right, bad ignition switch, or wire at the ignition switch, or relay (anti roll over relay???), fuse....like a bad wire to the ECU, or a dead ECU/PCM, or a really bad PCM ground!
 
If the relay is closing for that first second or two when you turn the key to the run position, you should see 12 volts going out of the relay to the fuel pump. So, you can check the relay voltage output pin.... if it is there, you can check for voltage right at the fuel pump connector...it should be there for that first second or two when the relay closes. If it is not there, trace the wiring back to the fuel pump relay.

If power does go through to the fuel pump for that 1 or 2 seconds and nothing happens, your fuel pump may be dead.

If there is no voltage coming out of the relay when you turn the key to run for the first second or two, that means either the relay is not closing, (relay may be bad), or the internal relay coil power or ground is missing and the relay is not closing, or the voltage feed into the normally open contact is missing, so nothing going in, means nothing going out if the relay closes.
 
But with a dead PCM, why would it still give me codes? Is it possible that the code portion of the PCM is working right, but not the switching ground thingy? The reason I ask is that I get the continuity at the relays, which tells me that that part is working correctly. How much voltage should the relays be getting and if they don't get much to close, then how much should I be reading? I am still checking the grounding at the PCM, and I am going to clean it up, down to basically bare metal and see if that helps it any. I was just checking to see if I am missing something else. How does one go about testing the ignition switch, or do you just replace that and be done with it?? The ground for the PCM appears to be good, not rusted or damaged, but I figure cleaning it down to bare metal isn't going to hurt it at all. Keep the ideas coming. I want to get her driving again.

Jeff
 
I tested both relay positions, the ASD and the Fuel Pump, and both give me continuity when the ignition is on, but none when off. Is this correct that they are closing then? I pulled the ASD one, tested it first, it was getting the continuity, so I went ahead and put it in and then tested the fuel pump relay, and it too gave me the same results. Any idea what pin on the relay is getting the voltage when the ignition is on??

Jeff
 
When you turn the key to run, both the ASD relay and the Fuel pump relay will have 12volt power on pins 1 and 2. When the PCM applies ground to pins 5 for that short 1 or two seconds, the relays should close. When the relays close, 12 volts will pass thru the contacts from pins 2 thru to pin 4, and will stay at pin 4 only as long as the relay stays closed.
 
on the bottom of the relay there are like 5 pins. Which ones are which, in relation to what you are describing? Looking down at the relay box(relay center with the fuses and relays), the bottom front to back slot, and the slot towards the front of the relay box which runs DS to PS, are the two that showed the continuity when the ignition switch was turned on, and none when it was turned off. Do I need to have someone turn the key to the start position to get the 12 volts and if so, which slot is the one I should be measuring it at?? Thanks for the insight. I am gonna also go back to the fuel pump wires and verify the voltage back there as well and see if its within specs.

Jeff
 
Note #2 from DJ
Testing my relays.
http://www.naxja.org/forum/showthread.php?t=1006312
OP by Dozer11B
----------------------
Post # 2 by Shorty
I have had great luck using a 9v battery between 85 and 86 while checking for continuity between 30 and 87. Use the continuity check feature on your DVOM with the tone feature (assuming yours has it) on 30 and 87 and touch the battery to 85 and 86. The tone should sound and the relay should click each time you touch the battery. This test will work with the battery + on 85 or - on 85 as long as you're not trying to check a diode suppressed relay (which I don't think you'll find on any of these Jeeps) It takes fourteen hands and some luck to hold it all, but it's really easy once you get the hang of it.
 
Ok McQue,

I got the email, the pins that have continuity based on the diagram are, 1 and 4 on the ASD relay. I will see if I can get some more checking done with it raining right now and see what I can find and report it back to you all with the finding. I remembered now how to test the actual relays, it was whether or not the socket it goes in is getting the power correctly or not. Thanks DJ and McQue.

Jeff
 
I get 12 volt on pin 2, but none on pin 1. Where next?? Looks like 1 is a feed from or to the TCM??


Jeff
 
Last edited:
Schematic says both relays will get these voltages when you turn the key to the run position:

pin 1 12 volts from fuse F6 in PDC
pin 2 12 volts from fuse F15 in PDC (ASD Pin 2 also protected by fuse F2 in PDC)
pin 5 ground signal from pcm for aproximately 1 second to energize relays
pin 4 will output 12 volts for 1 second while relay is energized and contacts close

PCM will remove ground signal after 1-2 seconds and de-energize the relay, and contacts will open. You should be able to hear or feel the relays click on/off.
 
Ok. Here are the findings after my extra set of hands came out and helped work the ignition switch.

ASD Relay

Pin 1, Key off: No Voltage
Pin 2, Key off: 12 Volts
Pin 4, Key off: No Voltage
Pin 5, Key off: No Voltage

Pin 1, Key on: 11.71 Volts
Pin 2, Key on: 12.14 Volts
Pin 4, Key on: No Voltage
Pin 5, Key on: 11.82 Volts

Fuel Pump Relay(With a Relay in the ASD slot)

Pin 1, Key off: No Voltage
Pin 2, Key off: 12.15 Volts
Pin 4, key off: No Voltage
Pin 5, key off: no Voltage

Pin 1 Key on: 11.72 Volts
Pin 2 Key on: 12.06 Volts
Pin 4 Key on: .003 Volts--had to set my voltmeter down to 2 volts to read
Pin 5 Key on: 11.75 Volts

These are my findings. This leads me to believe that the relays are getting voltage, if these numbers mean something else, let me know. More suggestions still. I am planning to bypass the TB sensors, and pull the Cam sensor(pickup coil) and see what I can do to try and attempt to get it to start. I am also cleaning up my spare NSS, but I am going to first "adjust" the one in the Jeep and see if that is the culprit, as I am finding looking at the diagrams that McQue sent me, they show that one of the wires goes or comes from the TCU, which if that also gets its power from the ignition switch, to me it would mean that maybe some of the starting circuit is my problem, which is being linked back to the NSS. But if I am getting the voltage at those circuits, then that would mean that the NSS is working correctly. Thoughts here now??? And thanks for all the input so far.

Jeff
 
If the relays were closing you will read voltage on pin 4, but only for the 1 second or so that the PCM applies the signal ground to pin 5 of the relay. When the PCM opens that signal ground the relay will open, thus no voltage at pin 4. So, if you never see the voltage at pin 4 it looks like the signal ground from the PCM is not happening or the wire is open.

You can try running a jumper wire from pin 5 on the fuel pump relay to ground and see if you can hear the fuel pump energize.
 
Ok here is another update.

I adjusted the NSS some, and got it to crank with the key. After a little bit, I don't have the reverse lights. I worked on it some more, and now I am not getting it to go into diagnostic mode to see if any trouble codes exist. I've unplugged the battery, and I will let it sit, and see if that comes back. I still need to pull the PCM's ground and clean it thoroughly and see if its a grounding issue. Still no spark, I even disconnected the TB sensors, and the cam sensor, and still no spark, sputter or anything.

I pulled the connector for the fuel pump which is just above the fuel filter, and I didn't know which of the leads I needed to check and see would show the fuel pump is bad or good. I am looking through the FSM now, and see, however I need to clean a whole lot of mud and dust from under the rearmost of the Jeep, as the PO didn't do a real thorough job of cleaning it after he offroaded it.

I did notice that the brick inside the cat is trying to come out the rear end of the cat. So I know that the cat needs to be replaced. I am wondering if the O2 sensor is my culprit. Reason being the tailpipe from the cat back to the axle is gone completely, and I wonder if there was a restriction in the exhaust somewhere causing a run/driveability problem. I guess I need to figure out which wires I need to check on for 12 volts to see if its getting it first, then see about jumpering it and see if it is bad, or what.

Keep the ideas coming and we will keep testing things till we get her completely fixed and running right.

Jeff
 
McQue,

If I ground the #5 pin on the fuel pump relay, how does the pump then get power? The #5 pin shows that it grounds for a second, to energize the relay. Will grounding the #5 really get the fuel pump to power up??

Jeff
 
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