The previous owner knew a Mini friendly garage, so it always past the Dutch MOT. It concerns a '97 Brooklands with stage 3 kit, ICON and 1:7 rockers, with high CO and overheating history. Overheating was caused by leaking expansion tank, so after I took a new one it was fine. First MOT: CO failure. Pulled the cylinder head and found 1 pushrod badly bent, lapped the valves, changed the hardened valve seals. Changed lambda sensor (100k Miles) and plugs, still high CO. Former Rover garage tested with Rover testbook, no troubles found. Nevertheless ECU was sent to workshop, MAP sensor found not reliable and valve clearances increased. After 3 month's and lots of money it was "road legal". Half a year later the stepper motor was falling in parts due to high vibrations (streets in Antwerp). One year later for next MOT, the same high CO. Now first I bought SP ACR4 code reader, found Throttle Position Sensor not reliable (no steady figures), changed the 1:7 rockers for my 1:3 Cooper S rockers, removed ICON, but no succes. Changed Cat, but now next to high CO also high lambda. Found that cooling water thermostat was wrong type (opening too early), so changed for original MPI type. But still high CO, high lambda. Found air leakages at manifold, it had been tightened too much, seats not straight. Lapped manifold surfaces, all small improvements, but still, CO just too high, and lambda too high. OK, what caused the high lambda: the Cat, so assembled old Cat, but also new Maniflow LCB (old one had too much tension) and new flexible piece (old one had some play). Now the lambda was OK! Still CO just too high, but while testing CO was changing, sometimes good, few minutes later too high.
All those tricks like running it red hot, using fuel additives, did not help.
Last thing I did not yet try, the fuel system. Found hose from fuel pressure regulator not sealing well, so did not work. Actually, pressure regulator did not work at all with vacuum on it. Dismantled it, used vacuum to get it working again, new O-rings, new hose. But still high CO. Changed original fuel rail system for adjustable pressure regulator, with a gauge, now I managed to get it within the proper values, but again, after several minutes, high CO.
Last remaining: removed the tank, pump, carbon filter. Checked lines. Hmmm, found this so called fuel trap on top of tank working the wrong way. Vapours are not flowing from tank to carbon filter, but fresh air from carbon filter will enter tank in case of vacuum. Strange. Checked internet for pictures, are all similar. It is also called cut out trap (so, in case of rolling upside down, preventing fuel spraying around???)
Turned the "fuel trap" 180 deg, so now flow is from tank to cannister. It is not a float, so I will take care not to overfill tank, to avoid fuel entering cannister. Now there is no pressure build up anymore inside the tank. And this is exactly what happened during MOT test, when I got CO properly set up, after a while pressure in tank increased, so fuel pressure and CO followed!
With half a year delay and a police fine, past MOT succesfully! But, what about this "fuel Trap". Is it damaged, wrong type, wrong way? Anyway, it works like it is now, but with reduced tank capacity.....
Thanks Forum members for all the shared troubles, it helped a lot, and maybe this will help others to keep driving.
Edited by Smike, 08 September 2012 - 02:39 AM.
