2 days ago, at the tail end of a 4 hour drive, the CX-5 (AWD Grand Touring) went from driving completely normally to just shutting off on the interstate. It was 75 degrees out and I still had a range of 60 miles of gas left, so not what I'd consider any extreme conditions. Lost power brakes and steering and was also in a construction zone with no shoulder so it was a real "treat" to get this thing safely off the road. I tried to start it multiple times over the next 30 minutes with no luck. It was then towed to the dealer. They called 2 hours later to check in and they said that it had started up fine for them after I left and their tech had driven it around starting it 4 times total. They pulled the codes and it had a P0192 stored (fuelrail pressure) so they figured it must be the high pressure pump and replaced that. Today I drove it home 4 hours without any engine issues.

Background: when we got the CX-5 new in 2017 we were taking a trip with only 15000 miles on it and it stuttered and bucked heavily a few times but didn't fully die. I was in the middle of nowhere with no Mazda dealer for 300 miles and luckily I was able to make it home (it started driving normally again after stopping and restarting). Back home, the dealer found the same code and ran a series of diagnostics on the system. They concluded the fuel pressure was "on the low side of the normal range" and replaced the HP fuel pump under warranty. They were never able to repro a drivability issue. At that point I figured it was a total 1 in a million fluke to have a new fuel pump die and didn't give it much thought. But now that it has happened again with less than 60k on the replacement pump I'm really starting to wonder. Given how suddenly and dramatically this presents itself it has really shaken my confidence in this vehicle. I don't see how I can trust letting my wife drive it 6 hours in the winter to visit her mom, or how we can transport our elderly dog to cancer treatments 3 hours in the summer heat if, at basically any point, we can just end up stranded.

Does anyone have any insight to offer on this problem? Does the diagnosis even make sense? I read that the HPFP is cam driven, so would it even be involved in getting the motor to start? Or would it mainly come into play once running and under load? I'm have lots of EFI experience but no direct injection experience. I don't know if it is possible for a DI motor to run at all (or even start) without the HPFP working properly.

Thanks for reading!

 

There's not enough information to speculate about the issues with your vehicle, because whatever diagnostic testing they did (if any) is unknown. The only thing I can say is that I've never read a prior report of an HPFP issue fixing itself, and then subsequently operate normally. And I'd be more than a bit interested to find out exactly how something like that can happen.

 

I was not familiar with this pump until after the repair. I thought it was electric and reasoned that if it overheated it could perhaps cool back down and start working again. But I agree 100% that a mechanical pump seems very unlikely to just start working again on its own. And that has been the pattern both times, with the original issue when new, and again this week - by the time the vehicle gets to the dealer, they can't repro anything. So they just swap out the pump. Under warranty the first time, at a cost of $1200 this time. So I am quite concerned that we may not have even fixed the issue and I've been charged for an expensive repair.

 

Yes, I certainly agree with you about them throwing on another pump, UNLESS they observed an abnormally low fuel rail pressure reading on their OBD live data scan tool. And that's the missing piece of information here (unless they wrote something about that on your paperwork). And I also agree with your concern that the actual cause of your vehicle's problems might not be a bad HPFP, and that the real underlying and undetected problem may still be there, waiting to strike again. This is a very unsettling situation for you be in, to say the least, but I certainly hope you never see this issue come back again.

One thing for you to be aware of is that these mechanical HP pumps also have an electrical spill valve component, integrated into the unit. This spill valve is just as important as the pump itself and, if it has a problem, could be the root cause of the low pressure code being set. But again, it's really difficult to understand how a spill valve can go bad, and then fix itself back to normal operation. Is it possible that the valve could stick, and then later 'unstick'? For that to happen with one pump might be described as farfetched. But this same thing happening with two pumps is probably something right out of Fantasy Island.

 

Talking with the dealer again today they mentioned accessing the MDARS that was stored along with the trouble code and seeing low fuel pressure reported at that time. But I still don't think that's 100% conclusive... after all, a pump can't make pressure with no or low input, so a failure of the low pressure pump or the jet system (as far as I understand the AWD models have a split tank) could make it such that the rail pressure drops even without an issue in the HP pump itself. The whole notion of troubleshooting via swapping parts seems dubious when the problem isn't reproducible in the first place. This combined with the parking brake fault they introduced while doing the rear brakes during this service has really tarnished my feelings for this vehicle...

 

Has anyone checked the fuel tank vent hose?

 

The dealer didn't mention that. When I was stuck on the side of the road unable to get it to start I did try removing the gas cap just in case there was some kind of vacuum/vapor lock issue. But it didn't change anything at that time.

 

What they're referring to there is freeze-frame data, which is just a snapshot of various PID values when the code was set, and a low fuel pressure reading would be very much expected at that moment in time. If you want to put their feet to the fire a bit more, you can ask if they ever checked the fuel rail pressure with their scan tool and found an abnormally low pressure reading, during the time they had your vehicle running. And if their answer to that question is no, you can decide how you want the conversation to proceed from there.

 

I had my new 2017 CX 5 for 5 years with no mechanical problems, but of course, we did not drive as much as you did.
The only problem was people running into me! I traded the dark blue metalic for a new Sole Red CX 50; real nice!

 

Hi all,

I had the exact problem that HiBoost described happening twice to me with subsequent recovery.
I've put it on the ECU as a software bug as both issues happened in similar circumstances:

• I accelerated hard (but not too hard) from low speed (0-20 km/h) to merge into trafic
• Then, I pushed on the throttle to up-shift and then released the throttle a bit too fast maybe?

I'm a careful driver and I consider that I didn't acted in a problematic way, but the two times when my car had issues started like this. Again, it recovered by itself, rather quickly, after stopping and restarting. The engine light went out by itself as well.
Yes, I get what m5xguy it's saying about problems fixing themselves, but that happened to me twice.

Third time the charm they say... Happened a week ago again in similar conditions but the fault staid. Limp mode, very rough start when cold, P0087 and some strange intermittent rattling from the engine area when trying to accelerate.

I'm quite good with cars (to the point where I've changed the head gaskets on my previous Rover and MG cars) but I didn't planned to get to know my bought from new car (2016.5 2.0 AWD, manual, Europe) so intimately, so soon.

The Mazda network here in France is not that good to be honest. They scheduled me three weeks from now (!!!) and If I can avoid dealing with them, that would be fantastic.

The problem is not with the low pressure (in-tank) fuel pump, I've tested that one.

I have ordered an used HPFP from eBay and I'm waiting for it. I'm really not looking forward to this but if there are no obvious issues with the eBay pump, I will use it to replace my own and see what happens.
Failing that, I will patiently wait for the dealer to fix my car and to hit me with their invoice.

Is there any way to test the spill valve? Would this valve sticking explain this issue; and the "unsticking" the fix?

m5xguy, I see that you are very knowleadgeable about this and you also provided useful thoughts on other threads on this topic. Any ideas? Thank you!

Your suggestions will be highly appreciated and I thank you for your kind help and consideration.
Best regards