Intermittent not starting - 2012 Mazda5

90210

Member
:
2012 Mazda5 Touring
Original owner. Mazda5, 2012, 103K miles.

Over the last year, at times, the car will not start on the first try. Has happened about 3- 4 times, completely random. But it starts right up on 2nd try.

Battery is from 03/2016, so about 2+ years old.

Today it didn't even start on 2nd try, but started on 3rd try. I am perplexed what it could be. Battery? Alternator? Other issues?

You put key in, turn ignition on ON position, all internet light, lights up. You crank it (cranks perfectly, no issues), but then it doesn't start. Second time, exact same thing, it feels like ALMOST wants to start, but doesn't start. Third try was the charm.

Any ideas?
 
So happened this morning again

Car started and driven 16 miles. Turned off. One hour later, had to crank quite a bit, then started
 
I'm hoping you can update with what the problem ended up being as I'm having the same symptoms. Doesn't seem like a battery problem to me as it cranks fine and is intermittent.
 
If the car cranks but doesn't fire up, it's not the battery. Ignore that.

Usually in a case like this, the computer is not getting all the correct information to allow it to give the go ahead to the injectors and the coils to start making explosions.

I'd get the fuel pressure tested. This is often a bad fuel pump scenario. Next time, try this...turn the key to on (don't try starting the car), let the fuel pump run for a bit...cycle the key on\off\on\off and leave it "on" for a while before starting. Sometimes this kicks the fuel pump to work and it starts right up.

If not, then the next step would be to put a wave form reader on it and look to see what the crank and cam sensors are telling the computer. If the wave form is no good, then it's probably one of those sensors or a sprocket has lost a tooth.

Beyond that, you could clean the MAF sensor. Or you have a flaky ECU.

Not much else. If engine timing and fuel is there...the computer usually tries to start the car.
 
If the car cranks but doesn't fire up, it's not the battery. Ignore that.

Usually in a case like this, the computer is not getting all the correct information to allow it to give the go ahead to the injectors and the coils to start making explosions.

I'd get the fuel pressure tested. This is often a bad fuel pump scenario. Next time, try this...turn the key to on (don't try starting the car), let the fuel pump run for a bit...cycle the key on\off\on\off and leave it "on" for a while before starting. Sometimes this kicks the fuel pump to work and it starts right up.

If not, then the next step would be to put a wave form reader on it and look to see what the crank and cam sensors are telling the computer. If the wave form is no good, then it's probably one of those sensors or a sprocket has lost a tooth.

Beyond that, you could clean the MAF sensor. Or you have a flaky ECU.

Not much else. If engine timing and fuel is there...the computer usually tries to start the car.
Wouldn't low fuel pressure cause drivability issues? To me, it seems like the pump is having a hard time getting started up, hopefully due to age instead of something like a weak voltage. See my other thread I just created;

Thanks!
 
It can cause driveability issues...but sometimes not. On startup it needs the most fuel and the computer needs to see fuel pressure. At idle, it may run just fine. Then if you rev her right out it may start missing at the higher RPMs under load. It also, once started can run totally fine since the fuel pump runs fine once it gets turning. It's the initial bump to get it turning that isn't working.

Another thing to try is when this happens, whack the underside of the gas tank really hard.

Your starter when cranking the engine takes WWWWAAAAAYYYYY more power than your fuel pump ever could think of using. If you can crank the engine over, the fuel pump should be getting plenty of power. You can always check its connections (not a bad idea) but unless you see corrosion at the connection points, I'm pretty sure this isn't an electrical issue. Fuel pumps only last so long but to know for sure you may want to get the fuel pressure tested.
 
I tried the hammer trick on a car a long time ago which didn't help. Never figured out what that car's issue ended up being, though. I'll keep a mallet in the car and show the missus what to do next time.

If the pump wouldn't getting full voltage, then I was thinking a bad connection (unlikely on a CA car) or something related to a sensor if the pump supposed to get variable voltage (but these cars seem pretty basic, thankfully). I'll look for a test/bleed port on the fuel rain when I get home, but otherwise, where's the best place to put a gauge? What's the pressure supposed to be on these?

Thanks for your help, @negusm !
 
Dunno where exactly to test for fuel pressure. Haven't had a fuel pump issue with this car yet. This guy does it with some hose, a T and a fuel pressure gauge.


Replacing the pump looks very easy. I'd probably just do it if I had north of 150k miles on the car.


$110 for the pump


The only other culprit may be the fuel pressure regulator. I don't know if it's in the tank or engine bay on these cars.

That is to say *IF* it's a fuel problem and not a timing issue.
 
Any chance you’ve pulled the spark plugs to see if there’s a leaky injector? If it’s leaking into the cylinder while parked the fuel line would be drained when it went to start, and might explain why it’s actually working when it gets to the second or third try (after the line has been primed by the pump).

Also have the large connectors for the ECU been disconnected? If they aren’t firmly reseated it can cause weird issues. When I changed my transmission mount I thought I had them back on, but apparently didn’t get them on perfectly. Caused a bunch of no-start issues. Sometimes no crank, sometimes it would crank but really struggle to start and then have a wonky idle requiring me giving it a bunch of gas to get to a stable idle. Removing the connectors and reseating them fixed the issue.
 
Back