FPR failure

Hey there.

I have recently purchased a 16V 1.8 KR *edit* running Digifant II and Digifant fuel pump *edit* that has an adjustable FPR on it. I is an aftermarket Autotecnica Monza with guage - and in my opinion is probably a bit cheap and nasty - but I don't know much better.

The issue I have is that I have noticed that the gauge on the FPR will show me that when the car primes, and when the car is running that I have 3BAR pressure. The issue I have however is that when the ignition is off, that pressure leave the rail almost immediately. This is confirmed as the hoses on the intake side of the rail go limp.

I have clamped the return line after the FPR at the same time as the ignition is turned off, and this leads to pressure remaining in the gauge on the FPR.

My questions are;
- is this gauge on the fpr going to show me the fuel pressure accurately when the car is off

- Digi II should run a 3BAR regulator, where do you buy FPR's in the UK and do you suggest adjustable over a standard one

- Who has a recommendation on a replacement FPR?

I have also got a fluctuation in idle, that as much as I think is the ISV, want to have the fuel issue resolved prior so I can discount that as a contributing factor.

Thanks in advance - Michael.

If your running a standard pump, and K-jet injection system there should be no reason for an aftermarket regulator as the metering head has one built in.

But loosing pressure after switching off would suggest a faulty non return valve on the pump, or dodgy accumulator?

rossirvine said

If your running a standard pump, and K-jet injection system there should be no reason for an aftermarket regulator as the metering head has one built in.

But loosing pressure after switching off would suggest a faulty non return valve on the pump, or dodgy accumulator?

It looks like Australian spec with a 16V engine running electronic fuel injection, though.

my bad - just seen his welcome post  ops:

Sorry guys, my mistake I feel like a n00b not mentioning that it is Digifant II with Digifant fuel pump.

Love the steelies ross! I run some similar.

ah no worries dude, sorry cant help you out with digi stuff.

Steelies are the way forward! mine are g60 15" wheels - yours look like mk1 gti steelies? had some on my old one

They are 14" MK3 rims, sadly in Australia a set of G60 rims is very unlikely to turn up given how they were only privately imported, but would love a set like yours.

Thanks anyway, hopefully some DIGI head will spot this and help me out. I may have to go to golfmk2.org.uk for an answer?

i dont think the digi pumps have anything in them to maintain fuel pressure after shut down, nor do they need to, unlike k-jet where this is critical.

3bar is higher than what digi2 runs, they use 2.5bar as std. extra pressure may have been dialed in for the 16v swap though.  does the pressure change with revs? the factory FPR should have a vaccum lead on it which changes fuel pressure depending on engine speed/load. without this i doubt its going to run right.

Personally I'd start by fitting a proper digi2 fpr on there and see where that gets you, assuming one will fit as I assume its some kind of aftermarket fuel rail?

what exactly is the issue you are having though, you just mention pressure loss when off? does the car not run properly?

rubjonny said

i dont think the digi pumps have anything in them to maintain fuel pressure after shut down

I agree pump keeps pressure until its off ! Pressure regulator sends any spare fuel back to the tank .

Thanks for this. I was just under the impression that like K-Jet there was a need to have residual pressure. If not, then I am cool with that.

I am experiencing hard to start so was thinking that this may be an issue. The other problem I have is that the car starves at around 5000 RPM, so it was playing on my mind that there was an issue with the FPR.

Your suggestion will be taken up and I will get myself an OEM FPR, now it is just a matter of determining if it should be 2.5 or 3 as you suggest. The current one has the vacuum line like suggested and it increases by .5 BAR when the throttle is open.

I also changed the idle control screw o-ring today that helped lower the idle RPM from 1500 to about 1100/1200 rpm. When the christmas break is over I will get a new blue coolant and o2 sensor so I know that they are in good order.

Appreciate the assistance.

have you got the correct idle & wot switch arrangement on the throttle body? the 16v lumps as std just had an idle switch, but digifant needs a wot switcvh as well so it knows when to add extra fuel. if this was missing or faulty i guess it could explain the dificulties you are having at 5k.  poor cold starting on digis is often caused by the blue temp sensor, so definitly worthwhile replacing. as for the O2, if you disconnect it the car will fall back to a base map, so if it runs much better with the O2 disconnected you can be pretty sure its broken

Doing some research turned up that the system is pressurised.



So now I need to decide on a replacement fpr, adjustable or not…

interesting stuff, not convinced this effects anything other than starting when warm though? the fpr is working it seems as you can see the pressure change with revs etc on the gauge, so the diafragm inside isnt split