Discussion
A new friend of mine has a 1983 350i which was running up until 12 months ago. Prior to its demise there were some intermittent starting problems. These were investigated but never properly resolved One garage he took it to at that time diagnosed a suspected faulty ECU. One day he took it on a 25mile run. It wouldn't start for the return journey and had to be towed home, where for a variety of reasons it has lain unattended and unloved 
. Can anyone advise where to source a replacement ECU to see if this is the problem or offer any suggestions as to the best way forward?
. Can anyone advise where to source a replacement ECU to see if this is the problem or offer any suggestions as to the best way forward? If it has died completely the fault will be easier to trace. Assuming all the obvious has been check (is there a spark, fuel etc) I would suggest working through the diagnostic procedures in the Rover SD1 Haynes manual.
ECUs are not cheap, and it may well be the problem. However you may be able to fix it yourself - mine was full of dry joints. 30 minutes with a hot soldering iron and it was sorted.
ECUs are not cheap, and it may well be the problem. However you may be able to fix it yourself - mine was full of dry joints. 30 minutes with a hot soldering iron and it was sorted.
Thanks for the advice. I haven't examined the beast yet, but at least now I know where to start looking for bits. Someone 'in the trade' had offered him a Range Rover ECU which he was informed are exactly the same and was considering buying, being frightened by the price of the alternatives. I have counselled him against this course of action. I must admit to thinking that ECU's weren't repairable but now I know they are I can ask my mate who's an electronic engineer to check it out. There are some guidelines in Steve Heaths Griffith and Chimaera 'bible' that would help him diagnose the problem. ( Yes I'm an imposter here I own a Chimp!) So before I get my hands dirty ,am I right in thinking that if there's a spark and fuel and the beast still won't start, the ECU may be suspect or could a duff ECU prevent either spark or fuelling? I realise that there are a number any other things that would need to be eliminated first. I'm new to this world being more used to fault finding on Dellortos. OK - go on call me jurassic, but with your help I'm hoping this old dog (well, cat really!) can learn a few new tricks.
The Rangey ECU may or may not be OK for the 350 depending on whether it's a '4CU' for the flap-type airflow meter FI system, or a '4CUX' for the later 'hot-wire' system. The two aren't interchangeable.
The flap-type ECU is repairable; Lucas went to some lengths to hide some of the component type numbers but a good techie would know ways round this. The big problem is the two main ICs that control everything: if they've gone pop you will struggle (Ferranti disappeared years ago!).
There is a voltage stabiliser circuit in there that would be worth checking; also the two power devices that fire the injectors may fail if the wiring shorts somewhere. It may, of course, be something other than the ECU preventing the car from starting... there is a long list. However, the sparks and the fuel aren't integrated on the Rover V8, so you can soon eliminate the sparks in the usual fashion. The ECU gets a trigger signal from the distributor (coil LT side, in effect) so if this was absent you'd get no fuel. A quick test that I use is to turn on the ignition and then quicly flick the throttle wide open with your hand. You should hear a click as all the injectors fire (ECU thinks you just asked for full welly). You could also be missing fuel of course: there are two relays that serve to power-up the ECU and fuel pump.
I've been putting together the circuit diagram for the 4CU as used on my 390; I haven't decided what to do with it yet as there are a lot of hours in it (still have to finish the AutoCAD versions) - may publish on the 'net or sell copies so I can retire early ;-)
Hope this helps...
Ian
The flap-type ECU is repairable; Lucas went to some lengths to hide some of the component type numbers but a good techie would know ways round this. The big problem is the two main ICs that control everything: if they've gone pop you will struggle (Ferranti disappeared years ago!).
There is a voltage stabiliser circuit in there that would be worth checking; also the two power devices that fire the injectors may fail if the wiring shorts somewhere. It may, of course, be something other than the ECU preventing the car from starting... there is a long list. However, the sparks and the fuel aren't integrated on the Rover V8, so you can soon eliminate the sparks in the usual fashion. The ECU gets a trigger signal from the distributor (coil LT side, in effect) so if this was absent you'd get no fuel. A quick test that I use is to turn on the ignition and then quicly flick the throttle wide open with your hand. You should hear a click as all the injectors fire (ECU thinks you just asked for full welly). You could also be missing fuel of course: there are two relays that serve to power-up the ECU and fuel pump.
I've been putting together the circuit diagram for the 4CU as used on my 390; I haven't decided what to do with it yet as there are a lot of hours in it (still have to finish the AutoCAD versions) - may publish on the 'net or sell copies so I can retire early ;-)
Hope this helps...
Ian
I'll keep you posted as to how we go on. Gassing Station | Wedges | Top of Page | What's New | My Stuff