General punto cutting out

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General punto cutting out

6151del

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hi all
been in the motor trade for more years than i can remember, but got a problem i cant solve, this car has been with me for 3 weeks and i'm no nearer, 1 week with a auto electrician who has to admit hes no nearer either, so any fiat techs out there who can help, car is a punto mk2 8 valve on an x reg, came in with common running on 2 cylinder problem, scanned it to find coil pack and ecu u/s, changed both coils and fitted after market ecu, started up and ran fine, configured ecu as i have done many times ( tickover till hot,rev, tickover rev etc, car ran fine, took it for a test drive after about 2 miles engine cut dead, mil lamp does not come on but key symbol comes on flashing, sometimes remove key re-insert and it will restart, sometimes not, tried second key with same results, checked numbers on new ecu with old and nos were'nt the same ,supplier apologised and reimbursed me, went to fiat who supplied an identical ecu to original, fitted this , configured it, went for run, exactely same results, at this point i am stumped so sent it to local sparky, he thought the problem might lie in the fact that the original radio had been replaced with a cd player and the new ecu could'nt communicate with radio and was going haywire, put original radio back in, did'nt make any difference, problem just the same, tearing hair out time, any clues boys cos i'm stumped
 
hi
fitted plugs about 2000 ago, they are definetely the right plugs
 
hi
cheers will have a look tomorrow, and post back tomorrow night
 
hi
been working on car again, fitted new ngk bkr5ez plugs ( as per autodata)
removed earth wire, nice and clean but put a second earth to same point and took it to battery, took it out for a run, just the same , engine dies key symbol flashes, and thats it, towed it back and after 15 mins started straight up , when its running its perfect, scanned it for the umpteenth time, no codes present !! it will tick over in the garage for hours , only packs up when its on the road, thought it might be crank sensor but its not showing on the scannner, and if it was why the flashing key symbol ???? any more ideas
 
thought it might be crank sensor but its not showing on the scannner, and if it was why the flashing key symbol ???? any more ideas
usually i would have screamed crank sensor from the first post, but the key code light is what made me hold back from suggesting it. it is not unusual for a faulty crank sensor to not show up during a diagnostic, actually it is very rare that it would show up, but the key code light is an unusual circumstance.

the key code light flashes to tell you that the immob is disabled, by that i mean it is not saying there is a mismatch between the key's code and the codebox, and it is not saying there is a prblem reading the key code, it is saying the problem is the immob's power supply or earth.

temperature related problems like this are usually due to a rusty connection that is creating more resistance once it is warmed up.

considering all of the above, and then adding the fact that the immob can often have power supply problms from a rusty fuse holder on the punto, i would check the immob fuse holder is clean and free from rust. failing that you need to inspect the immob power suppply circuit as a whole. a wiring diagram for the immob would help you a lot, i dont think haynes includes that diagram but i cant remember to be honest. i know the fiat workshop manual has that diagram, but i dont have a copy of it here at work so i cant post it up.
 
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hi
cheers jug, dont know which fuse is immob. fuse but ive pulled and checked all the fuses in the box at nside of eng bay and all fuses in panel by diaog socket, all clean metered them all ,all good, one more thing i can add, when it does cut out if you disconnect ecu and reconnect it allways starts straight up, ???? heeeeellllllllppppp
 
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