Okay, thanks for humoring me with details of how you checked for spark.

See post #21 above for a link to the wiring diagrams. You'll see all coils receive battery power together through a single fuse and relay. The ground side for each coil is switched individually by the computer. Pick one of the easily accessed coils, backprobe the connector (still installed) and check for full battery power while cranking. That should give you an idea if the problem is on the constant supply side or switched control (ground) side.

No idea what's happening with the PATS indicator light. If it was acting up well before this new problem, it's likely not related.

 

wont the PATS cut ignition power if activated? I thought i read that somewhere……

 

So if your fuel pressure is correct, you have no spark, but can't smell fuel. Check for injector pulse. If no spark and no pulse, check crank sensor. If crank sensor is ok, suspect Immobiliser or ECU problem. It may not be the ecu or Immobiliser box itself, it could be the wiring to or from them.

 

You probably did read that, maybe even from me. Having a brain fart at the moment, can’t remember all the details.

I vaguely remember PATS had two response modes if triggered. The first stage disabled either the ignition or fuel pump, maybe both, but NOT the starter. I think the logic was to let a potential thief crank and crank the starter, but with no possibility of the engine running. In theory the thief would give up and hopefully go elsewhere in search of a quick theft, versus drawing attention to himself making all that noise. I want to say only the fuel pump was inhibited, but I may be less correct than usual.

In the second response mode, the starter was also disabled. I’m not sure of the logic of the two modes. I do remember some of the PATS details were kinda hush hush in the literature of the day, especially the early models. Guess they didn’t want to let the bad guys know the secrets.

If you’re bored, peruse the training manuals at Jagrepair.com. Or maybe it was in one of the service bulletins here at the forum. It’s been a while since I looked into it. Can’t do it myself right now as I’m knee deep in an engine change on my pickup.

 

One more thought on the theory of PATS disabling the ignition. A simple observation might help prove or disprove it. The no-start condition seems to have been intermittent, at least until the past few days.

If the indicator light responded consistently (not necessarily correctly) whether the engine started or not, that would point elsewhere for the root cause.

If the indicator light responded differently for start vs. no-start, that would obviously point to the anti-theft system.

 

Hi everyone, So the mechanical fuel pressure guage from fuel rail was approx 50psi while cranking and the battery load test was approx 12.6v after 12 sec load. I disconnected battery and kept Pos and Neg cables connected for 2 days. And put battery on charger. The weather in NJ was warm and dry. I reconnected battery and car fired right up. I drove car 20 mins and let sit and it started right up again. I'll update over next few days. Is it possible moisture in one of modules has caused this intermittent issue?

 

Well, I suppose anything is possible, but personally I wouldn't go there yet. Check the spare tire well for water, as the trunk seal is known for leaking.

But if dry, I'd strongly suggest stepping back to review the overall situation. A new problem (intermittent no-start, ignition related) showed up out of the blue after some other work on the ignition system. I'd still lean strongly towards one (or more) of the new coils causing the problem, perhaps indirectly. See previous posts for some possibilities, such as the new coils overstressing an intermittent relay.

Have you tried swapping the ignition relay yet? You couldn't ask for simpler troubleshooting. Same with reinstalling three of the old coils on the easy side.

I'd also suggest watching the PATS indicator light very carefully. See if the behavior changes when the engine will and won't start.

 

I have tried swapping the ignition relay. Same crank no start problem. I reinstalled three of the old coils on the easy side still same issue. No water in trunk. The PATS LED doesn't blink at all but horn beeps when locking doors with FOB. This car will consistently not start again after running and sitting for 27-30min. It will crank fine but not run. If I retry starting after an hour or so it will fire right up

 

After all the guesswork is finished, the fault is most likely the fuel pump module.

 

Yep

 

Believe it or not, it sounds like you're making progress. You've been able to consistently duplicate the scenario that creates the fault. After setting up the conditions, you've got a magic hour or so to work through some systematic troubleshooting while the fault is active, i.e. confirm spark, fuel pressure, etc.

 

Have we lost you yet? I just noticed something odd about the 12.6V you recorded. I see two possible scenarios, and neither one makes much sense.

1) The voltage measurement was recorded while under load. If so, that's very high and makes me think something is wrong with the test procedure and isn't working the battery hard enough to give a useful response. 12.6V is typically the minimum you want to see with no load, BEFORE engaging the starter or load tester.

2) The voltage measurement was recorded AFTER removing the load, whether from the starter or external tester. Measuring the voltage then is nowhere as useful as recording the value under load.

With a "12V" battery, it's normal and expected to see the voltage drop as low at 10.0 volts under the load of a starter or external tester. For a fixed load, higher voltage = stronger battery. But seeing such a high number doesn't make any sense to me. Either the battery wasn't worked hard enough, or the value was recorded while unloaded.

Did you ever measure the voltage at the coils with the starter engaged? See post #41 above.

 

Hi u havent lost me yet. I just have limited time to mess with this car. Today it cranked over about 7 revolutions then starter froze a split second then car fired up and ran. Is it possible I have a weird voltage drop thru starter causing low voltage thru ecm?

 

An interesting development... Did the starter stall or struggle when it stopped, as if working too hard or the power supply was insufficient? Or was it a quick on/off as if the key had been momentarily cycled? Trying to get a feel if the starter itself was acting up, or something in the control circuit (including PATS) caused it.

And through all of this, have you taken a voltage reading with the starter engaged? That's going to be a YUGE clue about how best to proceed.

 

I'm just throwing this out there... But could it possibly be the ignition relay is bad? That was the problem with my car recently.

 

The starter cranked as u would expect. Then for a split second it was if the timing was off then next revolution it fired up and ran

 

I was lucky enough to find a brand new starter on amazon TYC 1-06651 Starter Motor it cost $27.00. Ill install it and let you know result. Thanks everyone

 

Hi Everyone. I have an update and problem seems solved. So from my original post when I had a cylinder 3 misfire and disconnected battery, replaced all 6 coils and plugs, reconnected battery and car cranked but didn't run. After car sat approx 30min I cranked it over and it started and ran fine, but it continued to do the intermittent crank no run. As a mechanic would think car didn'nt have this problem before work was done, It must be related to work I did. Well this turns out to be one of those rare times that it was just a coincidence. My last post i described a slight starter hiccup that occured 1 time, that got me thinking about a voltage drop or something electrical between starter and control module. I found a brand new starter for $27 and thought for $27 what the hell. I replaced the starter and the intermittent crank no run problem has gone away. It's crazy how a starter that always cranked engine over at a pretty normal speed could be the culprit of this problem that drove me crazy for weeks. Funny thing is My Wife said maybe it's the starter and I said I don't think so car always cranks over fine it just won't fire(run). As mechanics we all have a logical process when we diagnose problems and things that don't make logical sense to us we discount. Maybe sometimes a shot in the dark works. LOL Thanks to everyone that helped me with thoughts and suggestions.

 

First great job on the repair and reporting back!
But I got to say what a deal if you got a decent starter for $27!!!
All around win on this one for sure.
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