2006 ST. Intermittent fuelpump relay (fuelcutout) Periodically.

[John Sorensen]

My 2006 ST, fuelpump-relay cuts out intermittently, as rapid as it feels like ignition cutouts.
The relay works by having constant feed 12 volts, and putting the other side of the coil to ground, when fuelpump is engaged.
It is this ground “connection” that is giving intermitting ground. When running OK, this terminal is close to 0 volts (Ground level). When intermitting cutouts between 2 and 4 volts, depending how intense the cutouts are.
Each cutout are a fraction of a second, maybe one fifth to one tenth of a second, but the succession varies, as do the clicking intensity (cutouts) from the relay.
I have checked the wiring in the relay/fuse-box, and replaced the relay. No error-lamps are on.
I have bypassed the relay, then it runs OK, but only as a temporary solution.
Questions:
Does anyone know what controls the relay, and where “it“ is located? And what can be done.
Does anyone know where I can find a wiring diagram, and repair-manual. Download or buy.
Can be sent to my e-address, if possible
johnborups@gmail.com

Thanks: John

 

[Dialcaliper]

Don’t know much about the older Fiesta Ike yours, but the newer ones have a fuel pump control module under the driver’s seat.

If it’s similar to most other cars of 90’s-00’s vintage, odds are pretty good that the fuel pump relay is triggered by a signal straight from the ECU.

What you are describing sounds very much like a straightforward ground contact issue, and here’s some generic troubleshooting you can do for any pretty much any car of 1980’s-2000’s vintage, and (Unless it’s a German car - don’t get me started)

The most likely place to look is in the trunk! Pull out the liner, remove the spare and find what’s probably a small access cover over the fuel pump sending unit. Check for corrosion on the wires and around the rim. The fuel pump is usually just grounded straight to the steel body and not via a return wire. There’s either a local ground lug nearby for the fuel pump, or it’s directly grounded to the body by the sending unit attachment bolts. Clean up and reattach anything that looks suspicious and maybe also the stuff that’s not.

You can also look around in the engine bay wiring harness near (and possibly underneath) the fuse box for the ground locations where the some of the wires run into a lug bolted to the chassis. Some of them may need to be unbolted, checked for damaged wires, cleaned of any corrosion and then bolted back in place.

If none of that fixes the problem, it might be the fuel pump’s motor going bad, in which case you should replace the fuel pump (either a new OEM pump, or an aftermarket one, whatever your preference)

Sometimes you can find service manuals online, and even if it doesn’t specifically cover the ST, it might be still useful. The other good bet would be to contact someone like Pumaspeed. They’ve been around long enough they probably have the original paperbound factory service manuals in their possession, and while it’s unlikely they’d sell them to you, they might at least be willing to help you out with the information you are looking for

 

[John Sorensen]

Don’t know much about the older Fiesta Ike yours, but the newer ones have a fuel pump control module under the driver’s seat.

If it’s similar to most other cars of 90’s-00’s vintage, odds are pretty good that the fuel pump relay is triggered by a signal straight from the ECU.

What you are describing sounds very much like a straightforward ground contact issue, and here’s some generic troubleshooting you can do for any pretty much any car of 1980’s-2000’s vintage, and (Unless it’s a German car - don’t get me started)

The most likely place to look is in the trunk! Pull out the liner, remove the spare and find what’s probably a small access cover over the fuel pump sending unit. Check for corrosion on the wires and around the rim. The fuel pump is usually just grounded straight to the steel body and not via a return wire. There’s either a local ground lug nearby for the fuel pump, or it’s directly grounded to the body by the sending unit attachment bolts. Clean up and reattach anything that looks suspicious and maybe also the stuff that’s not.

You can also look around in the engine bay wiring harness near (and possibly underneath) the fuse box for the ground locations where the some of the wires run into a lug bolted to the chassis. Some of them may need to be unbolted, checked for damaged wires, cleaned of any corrosion and then bolted back in place.

If none of that fixes the problem, it might be the fuel pump’s motor going bad, in which case you should replace the fuel pump (either a new OEM pump, or an aftermarket one, whatever your preference)

Sometimes you can find service manuals online, and even if it doesn’t specifically cover the ST, it might be still useful. The other good bet would be to contact someone like Pumaspeed. They’ve been around long enough they probably have the original paperbound factory service manuals in their possession, and while it’s unlikely they’d sell them to you, they might at least be willing to help you out with the information you are looking for

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Thanks
No boxes under any front seat.
I tried to ask ChatGBt, and it replied: Controlled by ECU.
Although not 100% trustworthy, pointing in the same direction as you mentioned.
Tried to disconnect the 2 multi-connectors to the ECU, and connect again, and it hasn’t made a single cutout since, in 100 km. Usually not that lucky, but for now, lets see
If the cutouts returns, You gave me something to work with.
Thanks John