Hello

(sorry, I waffle.....)

I've got an S-Max Mk2 1.5 Ecoboost (petrol) 2015 with the 4 cylinder Sigma engine.
During lockdown it's not been getting much use but when I do use it, if it's been sat for around 5 days or more, she struggles to start.
Clutch in, in neutral, push start button and she turns over for maybe 7 or 8 seconds before she fires up. Bit lumpy for a couple of seconds then all cylinders join in and then ticks-over and drives normally.
I try to "blip" the throttle a bit but I've heard it makes no difference on modern cars. I certainly don't hold the throttle down like in the old days if your car was flooded.

Somethings definitely up!
As a test I've had the battery on trickle charge overnight before and she turns over keenly, just doesn’t start immediately. So battery is good.
Recently replaced the downstream O2 sensor and reset the codes but made no difference. There's no other codes present.
The spark plugs look OK - I mean, you can tell they're used but not damaged or too sooty etc. and they were changed around 20k ago. I'm pretty sure they're good. Air filter nice and clean.
I only use shell or BP fuel and have been popping a bit of Redex in regularly.

Once started, she runs fine, always been thirsty (29mpg mostly short journeys).
No smoke or strange noises. No smell of petrol.

Has done 103000 miles though.

Something to do with fuel I'm thinking. Like it's evaporating after a few days in the fuel lines or leaking back into the tank.
I've even tried having the ignition on for maybe 6 or 7 seconds before turning over which, on some cars anyway, starts the fuel pump to get fuel to the high pressure rail, but still doesn't help.
Is there like a one-way valve on the fuel injection system that could be knackered?
Could fuel drain back into the tank or evaporate if left for a few days?

If used every two to three days it's absolutely fine; fires up after a second and runs lovely.

Thanks for reading....

Richard

Hello

 

Been doing more research and I think it's the check valve inside the fuel pump. 

I got under the car while my assistant (wife) put the ignition on, without turning over. You can hear the pump switch on for maybe two seconds, then goes off. That's a common "feature" for many cars, apparently. If this is repeated maybe 5 times,then try and start the car it fires up almost instantaneously. So fuel needs to be dragged back up to the injection system where it has drained back via the one-way check valve over time.

This can be worse and can happen after some cars have been left for only a few hours.

So new fuel pump likely cause, a new one costs £230 from Ford. I might leave it a little while as we are using the car a little more these days so it won't be a problem. Should it get worse I may have to spend the money and change it.

 

Hope this may help others.

Ta

Richard

I think you have solved your problem. 

Could you add another oneway valve into the fuel line to prevent the fuel running back?