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

Also we still haven't found out whether this is a distributor ignition system.

A very quick and easy test for ignition breakdown on a dizzy system is to wire a very small incandesent bulb in parallel with the coil (something the size of an instrument / gauge lamp for example). It is preffered to wire a switch in series, so the lamp can be isolated at any time to demonstrate it is not influential in any way. Note, a side repeater or number plate lamp is too large; MUST be a small instrument like bulb.


When everything is working great, the lamp will be seen to be blinking very fast at idle, by 1500 RPM it will be seemingly permanently on, then between 1500 and 2500rpm it will simply appear to get brighter. At no time should you see any erratic behavior in the lamp - if you do, you have an ignition issue - maybe the feed, maybe the module (most common ignition fault- as someone above pointed out) or maybe the coil. Again though, it requires effort in diagnosing, not throwing parts at it.

Edited by turbodave16v on 27th May, 2017.

Believe me Dave, the Original Poster - thats me - REALLY does want to identify the issue. I've been building this car for 5 years and now its finally (sort of) on the road I'm desperate to drive it, especially as the sun is shining for once on my days off.
I'm not in the motoring trade nor do I have any previous projects or motor racing or mechanical experience. This is a first for me so its all self taught and learned mostly from the wealth of knowledge on here. I really am doing my best to figure this out, its very frustrating!

The return line is not blocked and the pipe goes into the tank about half way up but it goes in at an angle upwards so don't know how far inside to the top of the tank it goes?

Yup its MJ...

Maybe Turbo Dave can answer this, or maybe even Turbo Phil.......

Bi-Metal jet holder.... what are the symptoms of these that requires the modification to a fixed jet holder?

evad1980... do you have a heat shield between the turbo andthe carb float bowl?

Also, try another crank sensor and make sure the air gap is correctly set.

I think it could be time to whip the carb off and see what's going on in the float chamber. I really do think it's worth checking to see if there is any shite in the very small inlet to the needle valve. A bit of swarf or anything like that could of come from the pipes itself after the filter. It's very easily restricted but it may still be letting a little fuel pass which explains why you can rev it without any load. It may well be as simple as that.
I do understand how frustrating it can be as pretty much all of us have been in your shoes. Just be patient and methodically go through it step by stepabout it and you will sort it fella. Like you said, it was running great on the rollers at full chat so it must be setting fairly trivial.

If you could tell whether it was lean or rich loss of power, that would really help

In general, a lean condition tends to hesitate, jerky, feels like the car is slowing down the more you open the throttle, revs rise quickly but lacks real power, crisp sounding exhaust note. A rich condition tends to bog down, revs pick up slowly, lacks power, sounds very deep throaty, exhaust stinks of fuel, burns they eyes and visual black smoke.

Where is your wideband!?

There isn't a heat shield actually no.... carb will have to come off next!! And yes, it's time for a wideband lol..

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

If the return pipe enters the tank into the fuel itself, rather than the open space at atmospheric pressure above the fuel, it is far from ideal.

As already said, the ways these regulators work at the very low pressures a carburetor float bowl needs is quite different to how they work on a fuel injection system where pressures are much higher so small variations don't matter so much.

However, from re-reading everything, I think the problem is more fundamental and combining Colin's question about a heat shield, you now saying after 5-6mins driving, and the current warm (almost hot) weather we're having it sounds like you need to look at heat soak into the float bowl, or even the lines to and from the carburettor.

Once it dies (or starts dying), how long do you have to leave it before it will run normally again ?

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

I reckon it could be heat related.
I've got a stainless steel one on mine. Think I also put some reflective shiney tape too!

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

sounds very electrical to me,

Can you do a log?

In the 13's at last!.. Just

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I find it helps me to regather my thoughts when problem solving.

In the 13's at last!.. Just

Until you do the tests I mentioned...and when I mentioned, you're chasing your tail.

Doing a test in the garage when you know it's working fine is almost pointless.
Unless you can replicate the problem in the garage....presumably it doesnt stop if it's idling in the garage for 5-6 minutes ?

Heat...if the vehicle is moving, I'd doubt heat is the problem, there should be ample airflow in the engine bay to keep things cool, and if you're just tootling about...again no huge amounts of heat to worry about.

And even suggesting dropping tank etc is just mental without testing fuel pressure as I described.
Likewise pulling the carb apart for float level....pointless given explanation of the problem, and not checking pressure during the problem.

And if there is a 10-20 minute period where it will not re-start...this should make it easy to test for fuel/spark and pinpoint the actual problem area.

Wont start...air, fuel spark. Find out which is lacking.

Edited by stevieturbo on 28th May, 2017.

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

to answer sprockets question about the bimetallic jet holder; idle and restart after a few min hot soak is what really makes this noticeable. Although changing the jet holder really helped, honestly the best solution I found was to turn my fuel pump off 35 to 45 seconds before I intended on stopping the engine; usually as I pulled into a car park or up my road.

When I came to restart it, this always meant I had a fresh dollop of cool fuel in the float chamber which meant restarting was a doddle...

Edited by turbodave16v on 28th May, 2017.

I understand heat soak but would it really be so exact to cause daves problem time n time again? same time n distance etc? And to not start for such a long time? And presumably not being ragged about just being warmed up pootling about?

Hmmm the jet is a good point, i'd forgotton about the bimetalic doowhat...

anyone know how much the jet can move? I'm thinking whicp the dashpot off and see how far the let is down with a vernier, get it to do the fault and whoip it off again and see how far the jet is down then.

if its moved tweek it to where it was cold and see if it starts,

also another trick Ive used to check for fuel starvation, is to whack an unlit blowlamp up the inlet and see if it will fire, if it does... fuel starvation.

Thanks guys for all the great comments.

Just to confirm the car has no issue starting. The problem comes on when driving and will continue to idle when pulled over. It will start every time.

T-Piece trick?.............

From my experience, a turbo carb runs pretty cool while you're driving. Only when stopping does it start warming up. The symptoms described are not those of the bimetallic jet getting warm.

Evad
I recently had the same or similar problem to the one you are describing,After a full engine re-build
I had the car at my local rolling road,car was set up ran with no problems.
I then took it for its first run on the open road,about 3 or 4 miles into the trip the car started to spit and fart gradually slowing to a halt and would only run in first and second gear,stopped the car gave it a rev up and she ran perfect,put it back under load no power only runs in first gear and just about moved ,
Left the car at a local pub car park(hoping it would get nicked) and recovered it with my trusty tranny and trailer.
Dragged it off the trailer and tried to start the car , it burst into life I then took it out on the road and thrashed it with in an inch of its life , no problems no hesitation buckets of power,I then proceeded to run the car down my local town through the lanes which are tight and twisty having a bucket of fun
I then turned the car around for a steep up hill climb home,after hitting the first incline spiting and farting same symptoms no power only enough for first and second gear, after getting a large branch
from a handy near by tree I thrashed the bonnet and cursed the POS (only joking) having no phone signal (wilds of North Wales) I had to walk home almost miles and fire up the tranny again!
So I took it off the trailer and again it ran fine full power restored,took it back down the hill to town,turned it back for the climb back home and as soon as I hit the incline spit fart pop car does it AGAIN! I turned it off and sat there contemplating the walk back and thinking some thing magical might happen and it did,I tried to restart the engine no battery nothing no starter power no electrics
Wiggle the battery terminals was my inspirational thought well wiggle I did and the battery clamp just lifted off the battery live terminal I pushed it back on gave it a tap on with my wheel wrench,car fired up full power,no spitting no farting drove it home no walking
It turns out the ring clamp bolt was MEGA tight and looked good but it was half way up the tapered post ,so I slacked off the bolt got a flat blade screw driver and opened up the clamp pushed it right down to the bottom of the taper tightened it up the clamp and it would not move so it was now tight or ft as we like to call it
Got back in the car drove it 30 miles without a hitch , no more problems and I have done over 500 miles since perfect nlow.
I am not saying this is your problem but go back to basics as I did because every one had an opinion
on what was wrong with my car and no one person was right all I got was "uh battery clamp? what a dickhead" yes but you never told me to check it dickhead? hope this may help just check out the battery terminals and feed connections
regards
Roy