Cranks for long time before catching

[stash3630]

Hey all!

tldr; cranks for awhile before catching. Have replaced the battery and crank sensor. New spark plugs about two months ago. What’s next?

My ST sits a lot, but always fires up. Recently, it sat for about a month, but started right up. The following day, it was doa. Very strange as nothing was left on, but it was fine after an easy jump. I drove and parked it many times the rest of the day without issue.

But after my last errand, it cranked but wouldn’t catch. I waited about 45 seconds and tried again. It cranked for awhile but finally turned over.

I drove straight to O’Reilly’s where the battery and alternator tested good (despite another hard start).

I replaced the battery and crank sensor yesterday, but the symptoms remain.

It keeps starting but after long cranks. Ideas?

 

[Mega ST]

Any CEL's? Could be the common EVAP line failure.
https://whoosh-motorsports.myshopif...-to-convert-2016-fiesta-st-to-2014-2015-specs

 

[M-Sport fan]

I've never heard of it being a problem before, but could the CAM position sensors malfunction also cause this??

 

[Intuit]

Had a prior car that did that. The backflow valve for the fuel pump failed so it wouldn't hold pressure in the line after the engine shut off. If I cycled the key to on and just waited for a second before cranking, it would fire right up. This was verified by reading fuel pressure or operating the schrader valve on the fuel line after shutoff. Our vehicles have very high pressures and will have sensors on the fuel lines.

Before guessing, need to plug in a diagnostic harness and run ForScan.

Got these from Amazon. This one I use with ForScan.


This one I use with the motorcycle and "Car Scanner" app. (Windows PC and Android Phone)



Make sure the driver door jamb switch functions as intended and isn't intermittent. (engine running, simply close the door with the remote outside the vehicle and it should consistently double-honk)

Our cars prime the direct-injection engine by operating the injectors for a brief second if the driver door is opened after it has been shut down for awhile. That gives the fuel extra time to vaporize in the cylinders. You should be able to hear that as the door driver opens.



.

 

[stash3630]

I've never heard of it being a problem before, but could the CAM position sensors malfunction also cause this??

without really knowing anything about how they function, I had this thought as well. My first reaction was some kind of sensor because really the symptom is only the long cranking

 

[stash3630]

Any CEL's? Could be the common EVAP line failure.
https://whoosh-motorsports.myshopif...-to-convert-2016-fiesta-st-to-2014-2015-specs

I need to dig up my forscan. I’ll find it today hopefully. I’ve had my car idle low after fill up a few times which I think is a symptom of a failing evap (sensor?)? It’s been on my list to preemptively replace it. Do you think that’s a possible cause of the hard starts?

 

[stash3630]

Had a prior car that did that. The backflow valve for the fuel pump failed so it wouldn't hold pressure in the line after the engine shut off. If I cycled the key to on and just waited for a second before cranking, it would fire right up. This was verified by reading fuel pressure or operating the schrader valve on the fuel line after shutoff. Our vehicles have very high pressures and will have sensors on the fuel lines.

Before guessing, need to plug in a diagnostic harness and run ForScan.

Got these from Amazon. This one I use with ForScan.
View attachment 59153

This one I use with the motorcycle and "Car Scanner" app. (Windows PC and Android Phone)
View attachment 59154
View attachment 59155

Make sure the driver door jamb switch functions as intended and isn't intermittent. (engine running, simply close the door with the remote outside the vehicle and it should consistently double-honk)

Our cars prime the direct-injection engine by operating the injectors for a brief second if the driver door is opened after it has been shut down for awhile. That gives the fuel extra time to vaporize in the cylinders. You should be able to hear that as the door driver opens.



.

Wow. I do think my driver door switch has been wonky and intermittent. I’m gonna test all this today and report back

 

[Mega ST]

I need to dig up my forscan. I’ll find it today hopefully. I’ve had my car idle low after fill up a few times which I think is a symptom of a failing evap (sensor?)? It’s been on my list to preemptively replace it. Do you think that’s a possible cause of the hard starts?

In my case it is. It will throw a code specifically for that failure as well. Usually.