Bear with me here, I’m not overly clued up about this.

What should the fuel pressure be @ idle?

Now my car as far as I’m aware has the std fuel pump, adjustable fpr w/gauge and runs 850cc injectors. Now because it’s not standard would the pressure be higher?

Car is now running lean whilst on full boost and I’m trying to suss out what’s up.

 

static fuel pressure with vac pipe disconnected 3 bar (45psi)

 

And if it’s below 3 bar disconnected what does that mean? An issue somewhere?

 

If your cars been mapped it needs to go to where it was when mapped you can basically have any pressure you wish (within reason) and then map to suit. 9 times out of 10 an afpr is fitted to lower the fuel pressure with larger injectors or sometimes to squeeze a bit more out of standard injectors. Leaving myself open to abuse here but some of the Prodrive rally prepared used to run a static 6 bar fuel pressure.

 

It was fine when it was mapped, afr was bang on especially when on full chat. Problem is since then something has caused the afr to be out, car was on the dyno on Wednesday there and it’s up in the 13’s when on full chat.

During the mapping it was between 11-12

 

Well unless somethings been changed a new fuel pump would probably be in order.

 

If I get 3 bar on the gauge when removing the vac pipe what does that suggest? I haven’t tried it yet but from what I can gather it’ll mean fuel pressure is fine and the issue is elsewhere, if less than 3 bar then problem from tank to there, so fuel pump etc.

 

Could it be as simple as an exhaust leak ?

Or as says above the 15+ yr old fuel pump getting tired ?

 

Could be, I’ll have a look.

 

Pressure/flow is two different things and work very peculiarly. It is on boost that you need to watch your fuel pressure an in car fuel pressure gauge or a toucan etc is an important addition if on a high power car.

 

I tested the fpr there the now.

With the vac line removed the pressure is @ 3.2 bar
I then applied pressure via a spare wheel with 1 bar ish and the pressure went from 3.2 bar to 4 bar.

So I’m fairly confident the fpr is fine. I checked the vac hose itself and it appears fine.

So problem elsewhere.

 

That's not a real world test you need to be on boost with the injectors on high duty cycle. As stated flow and pressure are complicated. That was only a static test.

 

I’ll get someone to drive the car and give it the berries whilst I hide in the engine bay keeping an eye on the gauge

 

In car fuel pressure gauge and wideband O2 sensor

 

when was the fuel filter changed ?

changed mines after 3 years and seems to run better and meet afr target easier

 

Will be pretty tight in there

Can get a Scoobyworx pump for 100 quid

DiY in no time at all