Loss of fuel pressure
Turbo Mini Forums

I presume that you have the tube in the top of the reg connected to the plenum when not blowing down it?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Awaiting. Pics

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Just had another thought. Could the little filter on the needle jet be blocked stopping the float bowl being filled quickly enough.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

WWW.TURBO-MINI.COM

pics
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Well that went well then, not
having a job uploading pics sorry

images ^ ^

If I understand correctly what Tommy has said, the fuel pressure drops to zero while driving at 45mph or so, therefor if the strainer in the float valve in the carb was blocked, that would not happen.

we need to clear up all the misconstruction.

we now already know that the pump pressure with an open discharge was not 3bar and was a misunderstandig of technicalities. This then puts a question on everything previous in this topic related to 'pressure', since, how can you see what fuel pressure is at the carb when driving with the gauge where it is. was the refference to 'pressure' actually meaning fuel flow, and the pressure was infact fine?

If you measure the fuel flow with the pipe disconnected from the carb as I suggested (time how long it takes to fill a 5 liter jerry can), this will at the very least confirm whether the fuel pump and regulator can actually flow somewhere near the pumps rated figure, thus eliminating all but the carb

With the fuel line connected to the carb you say you get 4psi or so suggests the regulator is doing what it is intended to do.

At idle the flow through the carb is at its lowest, therefore nearly all the fuel will be rushing back to the tank on the return line (the pump has constant displacement so all that fuel has to be going somewhere)

As Wil and Phil suggest, if the strainer is partially blocked, at low fuel flow rates the fuel level in the float chamber can be maintained, but if the engine fuel consumption increases (Driving conditions), the fuel level drops until such a point that the carb is run dry (fuel demand greater than fuel supply).

One other thing perhaps to consider is whether the dashpot piston is rising propperly.

I'd suggest the carb is the problem at this stage but you NEED to clarify what you mean by fuel 'Pressure' in ALL your previous posts, and whether you are telling us undeniable fact (you saw the pressure gauge at 45mph drop to zero PSI) or whether it's an assumption based on an assumed theory?

Don't want to add more confusion - i am in the fuel float draining camp - so check the float valve area is where i am headed, but also add a possible uprated size float needle to get fuel into the bowl quicker standard is .7 uprated is .9 i think
http://sucarb.co.uk/float-chambers-spares/...ing-loaded.html

one of the turbos on ausmini found that as a fix

Thanks to whoever sorted out the pics.
As the car drives along, and I ask for more power (put my foot down) I can look at the air/fuel ratio gauge (lambda) and see it go slowly into the lean end, until it finally goes full lean (into red zone) and then the engine will cut out for a moment or two. I stop, look under the bonnet and note that the gauge in the reg to carb line has dropped to vitually nothing. With the engine ticking over, the guage will then rise slowly back to the 4 psi as set.
This is how I know it`s about to pack up.
I can then run at no more than 45mph, watching the lambda gauge flutter between normal position (about 12 on the gauge) to going into lean(about 15,red zone) if I ask for a bit more power. Get back home, leave it for a bit, check whats coming from the pump (flow, not pressure as we have worked out) stick it back together and we go back to square one.
Car is off to Slarks on the rolling road this morning, will be checking the thead, cos Neil there might also need some pointers too.
cheers

If it runs ok on the rollers and not on the road. It may well be fuel in the tank sloshing around, making pump go on air, and pump unlabeled to prime again? Baffels may be required. Fitting in the tank.

Is the pump in front of the tank?

In the 13's at last!.. Just

Also,you need to extend the pipe work out of the bonnet so you can see the fuel pressure whilst driving.

In the 13's at last!.. Just

The long wheelbase tank's fuel outlet has a dip tube that extends in and down to the centr of the tank. There is usually a circular recess in the botom of the tnk that can be seen from the outside.

The fuel supply you have welded onto the bottom may be an issue with fuel surging in the tank?

What's going off here with the blue hose? Shouldn't that be blocked of rather than t'd into the boost sense line? In my mind that would equalize the pressure in the carb body and plebnum, negating the restrictor ring in the plebnum and making sure it runs out of fuel on a run.

As above. To test it, put a clamp on the blue hose and try again. From memory, the anti-run on port should be blocked off.

You've got the balance pipe connected? Could that not be causing it to run lean under load, stalling the car. With the engine off the fuel pressure will naturally fall back to zero (mine does anyway) so I think what you're thinking is a loss of pressure is just due to the engine cutting out. When you switch the engine back on again the pump will bring the pressure back up.

Try disconnecting and blocking the pipe that goes from the side of the carb to the front of it on the top

Edit: and that blue hose looks to me like the tee piece trick?

Edited by Mike-998 on 2nd May, 2013.

http://www.turbominis.co.uk/forums/index.p...tid=469104&fr=0

Post a pic of the fuel regulator please

Ok gents
its at slarks and it does it no.w on the rolling road.
Hes on the case as i have to go to work.
He thinks its in the carb but yet to confirm.
Will let you know when mr slark has performed his magic.
Cheers

Two things from your pictures. Is that a turbo carb? I ask as the dash pot does not resemble that of a turbo cacarburettor. If it has a new dash pot or has been properly modified all good.

Second the blue pipe you have connected to the float chamer vent should be blanked and not 'T'd into the sense line for the fuel pressure regulator.

Third, check the balance pipe for cracks or holes as even a pin hole will cause the exact symptoms you describe even down to the speed at which it occurs.

Fourth and this is a common oversight that I will try to keep simple, the feed pipe from the tank to the pump has got to be of a larger internal bore than the inlet of the pump. Many may say this is not necessary but what you will here Is the tone of the pump change from a low hum to a higher level pitched whine, that pitch change has signalled cavitation in your pump which will cause it to stall. When this happens your fuel pressures will fall to zero and you can disconnected the outlet with the pump still running and no fuel will come out.

I have come up against everything you have posted so you need to verify what I have posted.

Edited by Mr Joshua on 2nd May, 2013.

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Fastest 998 mini in the world? 13.05 1/4 mile 106mph

How did you get on tommyboy

Confessed addiction to everything mini

i had to disconnect my balance pipe as it wouldnt run with it connected... try blocking it off...