Which way round on the fuel rail does the inlet and return go?

From memory, its "Rail In, Regulator Return" on nearly all EFI systems

But I'm having a bit of an issue with the RV8 in the track car which I only noticed accidentally.

Started it up yesterday and no problems there apart from overfueling and lots of fumes - I knocked the fuel switch off accidentally instead of the ignition kill, the engine revs rose to 2k (no idle valve fitted yet), the misfiring stopped instantly and the mixture was ten times better with no black smoke or unburnt fuel etc etc - even with the pump off the engine ran like this untill shut down (drawing fuel under vacume from the tank presumeably) - but the engine speed would not increase when opening the throttle due to fuel starvation (obviously with the pump off I expect this) and spluttered and then returned to the fast idle.

Switching the fuel pump back on returned the revs to 1000rpm, brought back the lumpy running and overfueling smoke and fumes

So there are only a couple of possibilites for this one really..

1) - I have the fuel lines on the wrong way (the feed is direct to the rail at the moment and the return is off the back of the regulator)

2) - the regulator is knackered and the pump is forcing full pressure (not sure what the BMW pump provides fuel at - its the standard in-tank pump from the 318is) down the injectors when they open - even tho there is a good return from the reg (tested by putting a return line to a milk bottle - filled it up in seconds)

3) - the regulator cannot cope with the pressure that the pump is providing fuel at and needs to be changed for an adjustable one ?

I'm a bit stuck asto what to try, without knowing what pressure the pump provides the fuel at, and what pressure the Rangerover V8 fuel rail operates at I have nowhere to start looking

 

Pump feeds the rail BEFORE the regulator

 

I thought that and that is how it is plumbed in so no problems there then, time to look at the regulator and see if that is buggered

 

Check the vacuum lines are ok to the regulator too

 

Brand new silicone line direct to its own port on the plenum - only runs about 10cm so nothing to snag or kink it - I did all the basic checks when scratching my head about other things that could be the issue

 

Good luck Paul, really the only way to check it is with a pressure gauge but then you need to know what pressures it all runs at

Having said that, the problem could be anything electronic too ... I hate cars LOL

 

I know - I've got a deragnedrover haynes comic but its about as usefull as a wonky table - nothing in there about fuel pressure or anything like that

Ahh well - I'll just order a cheap adjustable reg with a gauge on and go from there - should be able to nail the problem then hopefully

 

Found out that the fuel rail should be at 26psi with the vacume pipe on and at idle, and then 36psi with the pipe off or at wide open throttle.

I'm guessing that the in-tank BMW pump is providing a lot more than that

Will find out when the adjustable reg arrives with a gauge on it

 

any pump will deliver more fuel pressure than those figures - hence the need for a reg....

Alex