2012 Jeep Grand Cherokee - very occasionally starter cranks but engine won’t start

In My Humble Opinion
1

About 8 or 9 months ago my Jeep would not start- I push the button, the started could be heard cranking, but the engine just would not catch. This happened a few times in succession. Then I waited a few minutes, tried again, and it started normally.

I took it to the mechanic. Now, here’s the thing- this Jeep, while overall pretty reliable, has been subject to umpteen recalls, all of which I followed up on. One was a recall of a brake part that had been susceptible to water corrosion. Thought the dealer fixed that, then my brakes failed on me and I almost got in an accident. Turns out that, if the part “tests ok” the dealer was authorized to just put a little “rain shield” over the part instead of replacing it. So since I had also had a fuel pump recall, I I suspected it was another botched recall job, and I still had a failing fuel pump. But the mechanic (this was an independent I trusted, not a dealer) said the fuel pump tested fine, and it was likely the battery, since it was old and failing.

Get the battery replaced, and a week later, same thing- starter cranks, engine does not turn over, wait a few minutes, starts fine. Then it has not happened again for these past 8 or so months…until yesterday. I don’t drive as much as I used to since I work from home now, but I take the Jeep out to shop and run errands a couple times a week.

So…what could it be? I’m afraid, since the problem is so intermittent, that the mechanic might just shrug again and say “we can’t find anything wrong” or fix something else that’s not the problem. Do I just drive it until it finally fails and won’t start back up a few minutes later?

2

If the engine is cranking vigorously it ain’t the battery. Makes me suspect your independent mechanic just a bit. If the engine is just barely lugging over on a car that’s seldom driven, now that would make me suspect a discharged and sulfated battery that can’t hold a charge. Of course if it was that kind of a battery problem then with a new battery the engine ought to have fired up instantly like always.

After the modern car diagnosis gets very challenging other than by beginning with OBD. You’re not getting fuel or spark or both. Each of those depends entirely on the computers deciding conditions are right to make those things happen. And evidently this is true in all cylinders or the engine would fart and try to run a little sorta.

So for now it could be nearly anything: defective fuel pump, clogged fuel line, water instead of fuel in tank, defective crank position sensor, etc., etc., for another dozen general possibilities and another dozen make / model / year-specific possibilities.