Fuel pump dying?

[Gabbastard]

Had my mates AX 16v in today for a wee play. 16v engine, 708s, Janspeed mani, Dastek Q. Car mapped up fine about a year ago but manifold has been changed and idle was turd, so needed to adjust cam timing and have a map tweak.

AFR showed serious leaning out after ~4.5krpm to the point we had to abort. Even telling the Dastek to dump in fuel made next to no difference, the car just leaned out more and more. Fuelling is fine up til that rpm, so Im wondering if the pump - which admittedly is pretty old, an AX GTi pump (deffo up to the job as theyve been used on turbo AXs) - has just spat the dummy and cant keep up anymore.

Would this be symptomatic of a failing pump? Or maybe a failing injector?

Cheers.

[MartinObviously]

Could be either.

does the fuel pressure drop right off? that would be a sure sign of a dying pump.

else I'd suspect the injectors are maybe a bit slow to open?

[Gabbastard]

The guy checked it and said fuel pressure seemed fine, holding 3bar, but they can drop volume while maintaining pressure iirc.

[MartinObviously]

The guy checked it and said fuel pressure seemed fine, holding 3bar, but they can drop volume while maintaining pressure iirc.

Don't see how the volume could drop while holding pressure.

If an injector was open, and the pressure didn't drop that says to me the pump would be fine?

As it's still maintaining pressure the pump must be supplying the rail with more flow than what the injectors can allow past?

I would have thought that if the pump was dying, it wouldn't be able to sustain flow, if there's less flow it won't have the ability to sustain pressure if the pump supplied flow rate became less than the injectors flow rate at full throttle.

[Gabbastard]

Im kind of at a loss as to the cause of the problem, car was fine previously but now the fuelling cant keep up. Going to try getting some parts together (MAP, injectors, fuel pump) and swap them out hoping something shows as the culprit. Wideband gauge purchase now justified...

[MartinObviously]

dat AFR doe

[welshpug]

has it a fixed FPR? if not, get one.

yes the pump could just die, my ZX went through a day on the rollers with sandy brown without issue, did a bit on the road over to satchell engineering no issue, heading back to launceston did a mile and lost fuel totally, pump totally dead!

[Gabbastard]

Standard 3bar fpr in it.