Fuel cut off

[Rdaley1302]

Hi all,
I recently had a minor incident and it caused the car to stop starting, I’m almost certain it is some kind of fuel cut off switch as the car turns over but does not start, I can’t hear any type of fuel pump prime either. I have looked all over for a physical switch so I thought I would come to the forums for some advice

 

[Handy Andy]

Check your Owners manual - only works if your Fusebox
in the Engine bay - looks like the above.​

 

[Rdaley1302]

View attachment 10178
Check your Owners manual - only works if your Fusebox
in the Engine bay - looks like the above.​

Mine doesn’t look like this, what do you suggest?

 

[Handy Andy]

They changed the Fuse-box layout - back in 2013...
As to which relay is vague in the Owners Manual

​

Schematically - the Relay is in and on the Engine Bays Fuse-box, but as to which one - use a continuity checker to locate that Relay by probing F11 Fuse terminal to the Relay that takes the power from that Fuse on the Common of the Switched side of the relay.

• For Those still reading these posts...
• To help with the diagnosis - the above schematic is for a 2013 Fiesta - the Main Fuel Pump Relay powers several parts of the Power Control Modules Emission system.
  • Notice also that there is a FUSE that looks to the Fuel Pump for the MAF sensor - on later models (POST 2014) of the Fiesta - the FUSE tap is gone - for they no longer use the MAF sensor. It's been relocated to the Intake Manifold and has a name change - more like the IMAPT sensor - Intake Manifold Air (Or Absolute) Pressure and Temperature sensor that takes this function over.
• Notice the Splices in the wiring S126, S306 - there are several "taps" into the Relay output that send power to the sensors and the Injectors - so if you are having issues with the Power supply feed or don't know if the Fuel pump connections are getting power, you can back-probe (test the connector at) the sensors themselves on the Engine for Power. This can help provide the clues as to what and where power has stopped flowing.
  • If the car doesn't start and the Fuel pump seems to work the culprit may be with power from the pumps' relay not getting thru to all the splices - so it simply means you'll have to fix a splice to restore power to all the emission systems that use the Fuel Pump relay as the main ON/OFF switch for the engine to run.

 

[Rdaley1302]

So I should check my relays instead of looking for a physical switch?

 

[Handy Andy]

Yes, there are no fuel shutoff switches - or breakers - in a Fiesta - POST 1999 - because of the SRS system helps control the Fuel Pump by "talking" to the system and the relay is then controlled by the communication established by the SRS system as a fully engaged talkback system even looking at the Speed Sensors to help with Traction Control.

So if all else works then the Fuel Pump and it's wiring underneath the rear passenger bench seat - are suspect.

To Help you further, there are a couple of attachments to help you know what we work with over in the USA variant of the Fiesta - there is also the issue of the Air-Bag or Restraint Control Module which is the module that handles later model years of the Supplemental Restraint System or SRS - that schematic is also here in this post. Look for the RCM - the Module SRS uses to process inputs and then tells the PCM to Go or NO-GO on the Fuel Pump and Ignition system.

 

[Rdaley1302]

Okay thank you, will have a look in coming days 👍