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No-Start '97 2.5l

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1997 2.5 no-start nss pcm
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80K views 121 replies 9 participants last post by  RUBI 4 MY MRS  
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#1 ·
Ok, started my wife's '97 today and moved it to move my car up to the garage. I went to start it again to run into the store and it won't start.

Switched Horn/ASD/Fuel Pump relays all around and all test good. I can jumper the two terminals for the FP Relay and make the pump run constantly, but even then it won't start and there's no smell of fuel, etc. It's as if the injectors aren't firing. I had this problem before and it mysteriously went away, it's intermittent. Fuse for the fuel pump, ASD, etc are all good. I checked back at the harness going to the pump and I get voltage back there, as well.

Could it be that something is stopping the injectors from firing?
 
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#2 ·
Ok I checked a few other things, for some reason the last time this happened I checked and it was getting spark, now it's not.

Also, the fuel gauge seems to read E, though when I just started it to move it, it was showing 1/4. I did verify that it's getting fuel at the rail, I found the schrader valve.

The fuel pump will run when the two terminals for the fuel relay are jumpered but with the relay in place it doesn't run at all, not even a second or two when the key is turned on.
 
#3 ·
See if you are getting power to fuses 9, 10, & 11 in the fuse block behind the glove box when the key is in the on position. If not, check to see if your radio, wipers & turn signals are working. If yes, then the reason you are not getting power to fuses 9, 10, & 11 is almost certainly a bad ignition switch which is where those fuses get their power.
 
#5 ·
OK if you have power to fuse 11 & it is good then go the FP & ASD relays & pull them out. One terminal in each socket needs power only with the key on (not all the time) usually 86 but possibly 85. See if power from fuse 11 is getting to both when the key is on. If yes then go to the PCM. In the black connector in the A2 position there is a red/light green wire. Make sure it is getting power (also from fuse 11) with the key on.
 
#7 ·
OK good so far. Now since the FP runs by jumping that relay you are getting power to terminal 30 from fuse 16 in the PDC now check for power at the ASD relay terminal 30 from fuse 6 in the PDC which also powers pin A22 in the black PCM connector. If all good there you can try jumping the ASD relay (as well as the FP relay as before). The ASD gives power to the injectors & coil & some other things. Now see if it starts. Just don’t leave the relays jumped too long if it doesn’t start since all components will have constant power even with the key off.

Also check the PCM ground wires at pins A31 & A32. The PCM controls everything (ASD FP relay coils, coil & injector firing) by grounding them when they are supposed to operate. So if all else fails to start it you may have a PCM problem. See if the 85/86 terminals in the relay sockets are grounding. I think you have to test that when cranking the engine. The FP & ASD won’t stay closed if the PCM isn’t seeing a signal from the crank sensor. On that note, are you sure the FP wasn’t running for the first 2-3 seconds of cranking?
 
#9 ·
Something is not adding up. If the FP relay 85 has power with the key on & the PCM grounds 86 even for a few seconds the pump should run (if it runs jumped & the relay is good).

If the PCM is grounding 85 on the ASD then you should get power to the coil & all the injectors. So check that. Then the injectors should get a ground pulse on the non hot wire as the engine cranks. Maybe the crank sensor is bad but if the pump won’t pump even for the 2-3 seconds it won’t start, crank sensor good or bad.
 
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#10 ·
Ok, I ran back through everything to be sure and I still have come up with largely the same results. This time around, though, in addition to checking for voltage at a specific terminal (85, 30, etc) I checked for continuity from the fuse that feeds it. Everything checks out ok with a few exceptions:

1.) I was running out of time so I only had time to check the coil for power but when I pulled the power plug off the coil I got 0 volts at either side while cranking.

2.) The last time I successfully started it (Sunday) the fuel gauge worked (as well as it ever does). It doesn't move at all now with the key on. I even did the test where you hold down the trip reset and turn the key on and all gauges do a full sweep.

Where to go from here?
 
#12 ·
When you were checking for power to the coil, was that with the ASD jumped (30 to 87)? If so & there is power there then you need to trace the output wire from terminal 87 to the coil. There are some splices in that wire. It starts out as dark green/orange at the relay but appears to change at the 1st splice to dark green/black (the dg/or wire goes on to the PCM) past the next splice & on to the coil. The last splice goes to the injectors. When checking that wire pay special attention where the harness goes behind the engine. I’m not sure on the 2.5 but on the 4.0 the harness is known to rub back there & cause problems.

The fuel gauge wires go back there too, if I recall.

The fuel gauge not working made me think no power to fuses 9-11 but that is good so not there. Is the volt meter working (reading when the key is on)?
 
#13 ·
Had the same problem last week on my 97. Had a mechanic come over as all our troubleshooting turned out good. Turned out to be the ignition coil. Took it off and had 6 cracks in it. Put a new one on $50 starts right up.
Did it run okay when raining or really damp weather or was it difficult to start. From your first post you said it happened before?
 
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#14 ·
I haven't had much time to mess with it the last couple days and we are leaving for vacation tomorrow. I will try to do the extra testing stated above tomorrow morning if I get a chance.

@Digger84 It does crank over well. There are no aftermarket alarms or switches.

@Rubi4MyMrs I will have to check again but I think the volt meter is not moving when the key is on.

@TJJeepGirl It did run fine the last time it rained but it would NOT start through the winter, not sure if it was cold or snow that had anything to do with it. This has been an intermittent issue.. it just starts right up sometimes for days and then for a few days won't run at all.. this time maybe it seems to be done done.
 
#15 ·
See what works & what doesn’t in the cluster. OP & temp won’t show but FP & volts should + indicator lights (CEL, air bag, etc.). The cluster gets key on power from fuse 10 which you checked + data from the PCM for gauge function. If the lights come on & go off as they should but gauges don’t move there could be a PCM problem which could also explain the no start problem. I hate to point to a bad PCM unless all else is tried & that is the last piece to the puzzle.

Also check the power to the coil with the ASD jumped or test for continuity from there to the coil as mentioned above.

But go on vacation & finish this when you get back. It isn’t going anywhere.
 
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#16 ·
Okay, finally got back at this this evening.

Went through and retested EVERYTHING just to be sure and then tried the new tests. Tries my best to trace the wire from the ASD to the coil didn't see any signs of wear, checked the wire loom was rubbed a little but everything is intact.

With key on indicator lights come on but gauges do not move. The oil pressure moves up a little to 0.
 
#17 ·
OK so neither voltmeter or fuel gauge work but the indicator lights come on & go off as they should, right? Do you get power to the coil & injectors when the ASD is jumped (from post 12 above)? That is the most important question now.

There is another member with a similar problem & I referred him to this thread then went on from there. It is not totally resolved yet either but he was able to get his running with the ASD jumped so would like to see if that will work on yours too. Here is a link to his. If it does start that way you will probably have to pull the jumper to get it to shut off but it will help figure out what to do next.

http://www.wranglerforum.com/f210/no-spark-in-97-wrangler-se-please-help-708666-2.html
 
#19 ·
Ok to the coil is good enough for now. The same wire (color) supplies power to the injectors so that should be OK too. So with the ASD jumped & the FP jumped it still won’t start, right?

Recheck if the ASD is getting power with the key on (86 or 85) & also if it still gets power there with the key in the start position.

Have you pulled the 3 connectors to the PCM & checked the condition of those pins & posts? Make sure there is not moisture or corrosion anywhere in there.
 
#22 ·
You never got the fuel pump to pump without jumping the relay, right? Not even for 2-3 seconds after turning the key on, right? Because of that I don’t think the crank sensor is the problem & since the gauges don’t work with power to the cluster (fuse 10) that says the CCD bus signals are not getting to them from the PCM & the PCM is apparently not grounding the relays to close them either. I would say the PCM is bad.

One last thing that comes to mind would be to check the 2 ground wires for the PCM. They are in the black connector positions A31 & A32, black/tan. Make sure they have continuity to ground. Also check the red/white B+ power wire at A22.
 
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#23 ·
No, never got the fuel pump running at all without jumpers.

I have continuity to both grounds and power at A22.

In addition I tried to hook up a code scanner and got a message about not being able to communicate.

Looking around at replacement options I happened on a Youtube video where a guy shows how to fix commonly broken connections on the voltage regulator part of the PCM but I pulled this one out and found that it's not put together the same way as this one. I was hoping for a quick easy fix.

Any suggestions on where to get a good replacement PCM? I'm seeing way too many $399 price tags.
 
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#25 ·
I did find that post earlier. Took the PCM out and tried to figure out how to get the cover off. Apparently, the casing for this PCM maybe just '97's is one whole piece, not two like in the post. I tried a bit to pry it but I am afraid to really screw it up.

I did find a guy on fleabay with a listing to repair your own PCM and ship it back to you. Not sure how I feel about it but I DEF don't want to go the way of reman or even refurb for a pretty penny.
 
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