Losing power.... continuously.... back in the game!!
Turbo Mini Forums

If you kept the servo pedal and used it with the non servo master this is your problem iirc they are not interchangeable. But can likely be sorted as suggested by shortening the pushrod

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Oh right... would never have thought of that. So how much would I be looking to shorten it by? Not much at all says Tom.. a few mm??

Dave no, just happening at the same time. The loss of power is a separate issue.

I had issues with the brakes locking on on mine last year and turned out to be a combination of failing MC and a sticking pedal. The pedal was not returning fully and failing to release pressure fully.

now turning to the pedal assembly, i'm pretty sure the pushrod for the servo brakes is riveted to the pedal and when drilled out, the hole in the pedal is larger and needs the pushrod fork altered to reflect the larger diameter. Most people change the pedal to the earlier one - this may be your issue as Denis has suggested

Edited by Rob Gavin on 25th May, 2017.

Just remembered, Saturday before L2B I topped up the master cylinder. I reckon I put too much in because this brake issue only started happening after that... thanks for the comments chaps, they have jogged my memory..

Ok, too much blake fluid in the reservoir. Sucked some out and is now down just below the max line.. was actually well above max. Hopefully thats sorted that before I start messing with the pedal..

So I thought I'd run a test on the fuel supply before I drop out the tank and start messing with it.. I disconnected the fuel supply to the carb and ran a copper pipe connected to that back to the tank filler.. Like so..





I then ran the fuel pump on the battery for 15 mins, was going to do 10 but kept it going to be certain. The pump ran continuously without any change in tone and without slowing down and seemed to be fine. The fuel pissed out uniformly for the whole 15 mins and didn't splutter, gargle or anything like that... just like this..



So would you agree... the tank pickup, pump and filter all seem to be fine?
To me, I would say so, they seem to be eliminated... the pump never faltered, the filter seemed to be able to take the continuous flow and the pickup.. picked it up lol!

Disconnected the temporary pipe and reconnected the fuel pipe to the carb, pressurised the pipe and then turned the key. She started on the button.

Would you agree? Fuel supply eliminated??

Thoughts please...

Have you ruled out the vacuum in the tank though?

Not 100%... the cap is actually a vented cap and there is a small pin hole drilled that you may be able to see if you zoom in on the filler neck in the last pic.. maybe if I drove it with the fuel cap off to see what happens?

How is your return line plumed in? You've proven it works well with an alternate return line...

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

I removed the little strainer filter that sits on top of the needle valve which could maybe cause a resriction and I also fitted the bigger needle valve jet from avonbar.
It may all help.

Ok, answers to all...

Fuel return line is plumbed in the same as the feed without the filter. Out of FPR in braided pipe to copper pipe, copper pipe runs all the way to the back then and then some fuel pipe to connect to tank return.. with the cap off and pump running I can see the fuel moving in there so I know its returning.

FPR was originally set to 4 psi... I don't have a wideband to see that info unfortunately.

It happens every time I drive it now. Starts dying after 5-6 mins.

When it happens the engine will continue to tick over and you can rev the shit out of it and all sound great. The problem is only under load. It will start every time, so the spark must be fine.

Sound of fuel system? Not sure what you mean, can't really hear it. Can hear the pump when stationary.

I could try driving it with out the cap and see what happens? Im not sure if fuel level makes a difference tbh.

Although, now you say that. The night before this happened I filled it completely and it drove great for 20 or so miles. Then parked it up ready for L2B in the morning and same thing sunday morning... but then again it would still be fairly full at that stage..

What plugs are you using - and how old are they ?

NGK bpr7es... brand new when rolling roaded, prob done a total of 80 miles..

All fuelling issues are pretty easy to isolate with a couple of gauges, tee barbs and a few yards of hose.
First gauge id install is on the pressure at the carb inlet. Second is the high pressure feed at regulator from pump.
Pop the gauges on the your wiper arm and go for a drive. This Will tell you very quickly if you have a fuel supply problem if the gauges show a change of behavior at the same time you start losing power.

Two other locations where you will benefit from monitoring pressure if you continue to have issues are the infeed of your return line (at the regulator) to the tank, and between the tank and pump. The first will tell you if you have a restrictive return, which will start messing with your fuel pressure settings, the second will tell you if you have a restrictive supply to your pump, which will start causing cavitation ultimately limiting the flow potential of the pump.

Personally I find verifying all of these give great peace of mind, and are worth doing when you are starting to have what sounds like a fundamental fuel delivery issue.

Edited by TurboDave16V on 26th May, 2017.

I would certainly change those plugs. 7's can wet very easily when left ticking over for a while and also driving in traffic and when they start to fail it gives various symptoms of fuelling ect.
It's happened a couple of times to me so I use bpr6es plugs if I know I am going to be driving in lots of traffic.
It's worth a try for the cost of set of plugs.

Ok... so maybe I should investigate the return from the regulator to the tank. I proved, or at least I think so, that the supply is doing as it should. Deep down I'm thinking that the problem is something to do with the regulator.. Should the return be flowing back to the tank at the same psi? i.e, if set at 4 psi to carb, should I be seeing 4 psi going back to the tank?

I could try the plugs too, although the problem I'm experiencing has not happened to me in traffic. But, worth a shot I guess.

what size pipe are you using for the return? and is it the standard size feed?

I know some people on here fit a larger return when using the standard feed.

Both lines are 8mm ID...

The return pressure to the tank will be inlet pressure to the regulator (pump pressure) minus the regulator outlet pressure.

The fact that I have driven the car on over a 20 mile run, on the motorway too giving it beans surely rules out that the pipework is restrictive in some way? Because when its going... its going.

No,

The return line to the tank is (or should be) open ended.

The tank should be at atmospheric pressure (if it is properly vented).

Therefore the return line should be very close to atmospheric pressure, ie, zero on a normal gauge (or 1 bar on an "absolute" gauge).

There will be a tiny amount of pressure at the regulator end as there are always some frictional losses in any return pipe but if the return pipe is sized correctly it should be too low to measure on a normal gauge.

The regulator design is a simple "spill back" type so will only work correctly if the return line is clear and un-restricted so no significant pressure can build up at the regulator end of the return line.

If you are measuring any noticeable pressure in the return line at the regulator end, the regulator will not be able to work correctly.

One question that I don't think has been asked yet, where does the return line enter the tank ?

It should be above the fuel level so it is entering the vented space at atmospheric pressure and that is why it should have zero pressure (apart from the friction losses) at both ends of the line.

Schrödinger's cat - so which one am I ???

Pipe work could be blocked partially on the return/kinked.

Here is an interesting fact.
The metro turbo, along with the maestro and Monty turbo versions all used a return line larger than the supply. This is an assured method of ensuring the return line is less restrictive than the supply, and hence allows the regulator to not be influenced by variance in the return pressure that should be zero or as close to it as possible.
Time and time again over the years of turboing minis, folks have reversed the lines, and it always gives fuellling issues. When I ran the same -6 bore lines in my mini (for convenience sake more than anything) I was looking to put a restrictor at the end of the supply line, but tested it first - sure enough; 3-4 psi of back pressure. Now in an EFI system running 45psi, this is probably negligible. But in a carb system when you're trying to regulate to almost the same base pressure, it will cause huge sensitivity in baseline regulated pressure. Suffice to say I ended up with a pretty sizeable restrictor.

If the OP REALLY wants to identify the issue, he will do some simple diagnostics which will 100% identify or eliminate fuel supply.

Just because something works while it's parked in your garage, doesn't mean it's still working exactly the same when your engine starts having trouble.