14 replies to this topic

[Danuneek]

Hi, before everyone has a go I have searched the forum for similar articles and if you dont want to answer again then dont, for those who do thanks because its driving me up the wall. Anyway, my car is an 93 Cooper SPI converted to HIF44 carb stage 1 and is running really poorly. Basically, it starts perfectly and ticks over nicely but a bit fast. The power is there as well but its kangaroo-ing and apparently backfired when my dad was driving it today. Also, it seems to have a higher drive with the gears, usually where I would put it into 4th its fine in 3rd and so on with 2nd. It actually struggles a bit in 4th. My mechanic said a couple of weeks ago it was over fueling and needed tuning, he said he could do it but I preferred to get it rr-tuned but haven't got round to it yet. Over the past week I haven't really used it much, just swapping cars around in my drive. And taking it out today it seems rather bad, too bad to travel to mini sport's rolling-road. I'm gonna get my mechanic to tune it 2moro if he has the time, but for now is anyone familiar with this issue and does it sound like its typical of over-fueling?

Thanks for reading, Dan.

Edited by Danuneek, 21 December 2008 - 09:06 PM.

[Dan]

How was the carb conversion done?

[Danuneek]

How was the carb conversion done?

I bought the car with the conversion so not sure. But it was running fine when I bought it, just started getting gradually worse with the cold weather.

Edited by Danuneek, 21 December 2008 - 10:08 PM.

[Dan]

My thought was that if the fuel system hasn't been changed there would easily be enough pressure to flood the carb but the cold weather shouldn't affect that.

[Danuneek]

My thought was that if the fuel system hasn't been changed there would easily be enough pressure to flood the carb but the cold weather shouldn't affect that.

Na, I dont think its the weather either. It runs fine standing and revving from still, ticking over fine just a bit fast, its only moving that the problem occurs. To be honest its been like this for a while, getting slowly worse and worse and with it standing for a week.

[dklawson]

Is the backfire out the carb or the exhaust? When you said "kagaroo-ing", do you mean surging forward and backwards when you put the car under load at speed... perhaps when accelerating or going up a hill?

[WiredbyWilson]

sounds like it is a lack of fuel, as is fine revving when stationery, but lacks power when driving.

mine did that but it was as i ran out of fuel , maybe check fuel filter (if there is one) as it may be full of crud - and being an spi it may have had one as standard and not been changed for a long time!

[Danuneek]

Thanks guys, I reckon its a mixture between a fuel problem and faulty HT leads as today my dad was taking it to the garage and it wouldn't start. He had a look under the hood and played around with the Ht leads and it started perfectly apparently. He even said it wasn't kangaroo-ing or stalling at all driving to the garage, just ran fine. So its having a check over tommorow and a tune to sort out the fueling issue, I'll keep you guys posted as is interesting to see whats actually wrong and how it concludes. Typical bloody mini eh!

[Danuneek]

Is the backfire out the carb or the exhaust? When you said "kagaroo-ing", do you mean surging forward and backwards when you put the car under load at speed... perhaps when accelerating or going up a hill?

Yeh, its like a judder forward and backwards and it does it on any surface. I haven't heard the backfire personally, my dad heard it but I reckon it was more of a 'pop' like mini's do particularly one that has fueling issues.

Edited by Danuneek, 22 December 2008 - 05:43 PM.

[T.Harper]

Ensure your vacuum advance from distributor to carb/inlet manifold is still attached.

Make sure the dashpot is filled to the top with oil, just use engine oil for the time being.

Get it idling at about 900 rpm, then unscrew the mixture screw 1/4 turn and wait and listen to the engine. Keep unscrewing 1/4 at a time (listening to engine) until you hear the engine speed drop, then screw the mixture back in 1/4 turn.

Then take it out for a drive and tell us how it is. Keep an eye on temperature too. The aim is to get it driving half decently so you can get it to someone that knows their stuff about SUs and distributor advance curves.

[Danuneek]

Well its been in the garage and apparently the carb is knackered and needs replacing at some point. He's sorted it for now but has suggested getting a new one. Its a 1 3/4 HIF44, so where do I go from here. Is there any point giving it a resto or shall I just buy a new carb, is the HIF38 carb better than the HIF44 carb?

Edited by Danuneek, 23 December 2008 - 02:09 PM.

[dklawson]

I'd say you should start by talking to another garage.

There are parts that wear on an SU but not to the point that they are beyond repair or service. The 38 and 44 designate the throat size of the carb in millimeters. Most people would probably add an HIF44 to gain performance (air flow) over the HIF38.

If you can do without your car for a while, consider having a professional carb rebuilder (or Burlen) rebuild your carb.
http://www.burlen.co.uk/
... that is... if anything is wrong with the carb at all.

When someone quickly dismisses an SU as worn out, I suspect they don't know much about them. There may be nothing wrong with your carb at all... which is why I think you should talk to someone else. A garage familiar with SUs is likely to have suggested repair/rebuilding instead of replacement.

Another point is that a large number of problems blamed on SU carbs really lie somewhere else. Before trying to tune an SU you really need to do the following totally unrelated tasks:
1) adjust the valve clearances (on a totally cold engine).
2) inspect and replace any suspect ignition parts (cap, rotor, condenser, points, spark plugs, plug wires)
3) carefully set the gap on the points (check with a dwell meter if you have one).

SU carb adjustments should only be attempted once those tasks are complete.

[Danuneek]

Just brought the car home now and I can honestly say it drives like a new car, i'm so chuffed with it. Also we took a detore on the way home to mini spares and bought a new coil as that was causing the kangaroo-ing. I've fitted that and in addition to the garages work its amazing. It's made me realise just how bad it was before. Thanks for everyones help!

[T.Harper]

what did he do

[Danuneek]

what did he do

As far as I can remember, he dropped the carb so now its idling at 900rpm and its so much quieter from standing than it was before and ticking over a lot better. He gave it as best tune as he could, so there is a lot more power there. Though, he said that to get the best out the carb he had to tune it so that it's above emissions level as the carb is pretty worn. So i'll have to sort out the carb before its MOT but thats not for a while and at the moment i'm just enjoying it. He was really clear and helpful and even advised me to buy a book called 'tuning the a-series engine' by David Vizard to learn more about it.