Hi all,

I really wish my first post here wouldn't have been one describing a problem (and I promise the rest will be more upbeat) however, I wanted to pick your brains with regards to a behaviour I've started seeing with my 2012 Mazda 5 1.8 Petrol TS.

Bought the car a few months ago and although I originally wanted a Mazda 3, the lockdown made things slightly more difficult when tracing down what I wanted and then it happened I stumbled across the Mazda 5 with only 72k and one owner. Got the car services at a Mazda dealership and outside of a suggestion to change the tires (no surprise there as I understand they do go through them a bit) there was nothing else flagged.

Now the problem itself is quite random: sometimes, although it's usually on a warm engine start, the starter will do its thing but the engine will not start, like it's not getting fuel. If I stop, switch the ignition off and try again within 2 seconds, it will start without any problems. When this happens, it predominantly does so when the engine is warm i.e. grocery run when you leave it for 20-40 minutes before coming back, petrol top up, etc; although I recently had it when the engine was cold for the first time.

Initially I blamed it on a dirty filter or garbage on the fuel lines however, as part of the service at Mazda, it did receive a full fuel flush and engine flush (which I assume would clear down anything?). When I asked to change the fuel filter as well, Mazda quoted me around 200£ for this which I felt was a bit excessive and decided to cancel that for the time being. I also checked for any errors using the ODB2 port and there's nothing flagged up.

After doing around 2500 miles there is something I observed and that is the start failure not happening if the tank is towards the full end of the spectrum, leading me to believe it could be down to the fuel pressure within the tank failing to send enough fuel to the engine. I assume a 2nd try will force the pump to create just enough pressure for the engine to start although I have to admit this is only a theory.

Happy to get your thoughts on this as I do hope it's not something that turns out to be expensive to fix as I'm not too keen on having to roll the dice for a good start or knowing it could stop altogether exactly when you need it most.

Cheers

 

Get the fuel pressure tested, both with the engine running & post shut down.

I wouldn't be surprised if the pump assembly is bleeding off fuel pressure when turned off.

 

Thank you, will definitely have a look at that. Might need to check if that's something I can do myself with a few tools from ebay or best to take it to a service.

 

You will need a fuel pressure gauge kit.