Diagnosis support requested…

[Geffellz18]

for an ‘07 Mazda CX-9. 3.5L V-6. Roughly 212000 miles on the ticker.
Just got back from a trip to VA & ran fine on the trip. Has had a slight miss for awhile like a coil pack starting to go out or spark plug miss. Nothing too major.
Wife pulled out of the driveway last week and headed up the hill out of the neighborhood. About halfway up the hill, she said the engine light came on, it shuttered and shut off. Was unable to restart it but got it coasted back down into the yard.
Put the code reader on it and the only code was cylinder 3 misfire.
Since I’ve had the car for over 100k miles with little to no major issues other than a head gasket leak that was repaired quickly, figured it just needed some new spark plugs & since I was going to have the intake manifold off & cylinder 3 was on the firewall side of the engine, I went ahead & ordered & installed new coils too.
Changed them all this weekend. Still won’t turn over. Moved on to the next potential culprit & ordered new relays. Still nothing.
It will try to crank & seems to even spark, but won’t turn over.
My next guess now would be possibly the fuel pump went out.
Any ideas on where to aim my focus next.
Should be good on the air & fire side, so that’s why I’m leaning towards fuel.
If I’m in the right direction, how hard is it to test for that? Would a fuel pressure gauge test kit work to test before blindly buying a pump to replace?
Not looking to put much more into it, but was hoping to get one more year out of her before putting her out to pasture!
Just seems to be a minor issue as it pretty much ran as normal up until that point and hasn’t given us any issues during the time we’ve owned it.

 

[transfixer]

I would suspect something timing related instead of fuel, since it intermittently was missing for a while before it quit, those have a timing chain as opposed to a belt, but the guides and tensioners that keep it tight can wear out, and the chain can stretch, if it has jumped time it would turn over but not want to crank, you're going to have to get further into it I'm afraid. I don't know if those are interference motors ( whether the valves can hit the piston if it jumps time) but if they are some of the valves could be bent or damaged if it jumped time also

Might be able to determine whether it has or not by watching the datastream with a professional type scanner hooked up to it while trying to crank it, not sure .

 

[Geffellz18]

Much appreciated @transfixer !… The timing never occurred to me since as you said it has a timing chain vs. belt, but makes sense from what you’re saying.
Definitely not going to dig into it that deep as the vehicle isn’t worth that type of expense.
It’s not our primary vehicle anymore and hasn’t been for awhile. We typically used it for a travel vehicle.
I typically drive all my vehicles till they die vs. selling them so it may be time to donate her to one of those foundations that help kids learn job skills!

 

[transfixer]

I don't know what used motors are running for one of those ? but it might be worth checking into ? if the vehicle overall is in good shape it might be worth finding a fairly low mileage motor and having someone install it ? Used vehicles are bringing good prices now , people are much more willing to buy used than new , and I can't blame them, those Mazda 3.5's are supposed to be Ford engines, and I don't hear a lot of negatives about them, other than the Timing chain and tensioners do wear out at some point

 

[Geffellz18]

Good point-It’s I’m pretty good condition overall for its age. Paints fading on the box and top of the cab, but other wise in good condition for a 15yr old vehicle.
It is a Ford 3.5L-I’m actually surprised I haven't had more trouble out of it myself due to this, but have had other Mazdas and they all have been pretty reliable, one additional one that was built on a ford drive train-Maybe they do something to them that’s helps their quality .
I forgot to mention that when I first got home to try to diagnose, I actually did get it to crank once and let it idle, giving it slight gas to keep it running. It was running very rough & ideled for about 10-15 seconds with no gas before shutting off. After that, I couldn’t get it to turn completely over again. Not sure if that helps with other potential issues or not.