Remanufactured ECU's
Discussion
After replacing my knackered ECU with a remanufactured one the car ran great for a couple of hundred miles, then a breakdown, AA got me home and i called out trusted auto electrician and guess what,knackered ECU! The unit is still under warranty but they claim it is the car itself at fault as it keeps damaging them, any one suffered this before? Auto electrician reckons all wiring is correct but was concerned that the inertia switch had been tampered with and maybe wired incorrectly which could damage the ECU but surely if this was the case the car wouldn't work at all, if someone could have a quick peek at their inertia switch and let me know which way round theirs is wired I can dismiss this theory, any other suggestions would be welcome except the one advising me to sell it and buy an SLK! Anyone had problems with remanufactured ECU's? Simon.
Don't buy the inertai switch theory, if yours is anything like my V8S (which it should be). The ECU has an output which controls the fuel pump relay. The relay feeds 12v to the pump. The supply to the relay is fused, and the inertia cut-out is between the relay and the fuel pump. On mine the immobiliser also cuts the supply to the relay, but yours may be different.
With this arrangement, I can't see any way at all that the inertia cut-out can harm the ECU; they're only connected via the relay.
With this arrangement, I can't see any way at all that the inertia cut-out can harm the ECU; they're only connected via the relay.
Excellent point there mongoose, I have read on PH that there should be two metal ones, however I have one metal and one plastic, surely something as simple as this couldn't be the cause? The ECU company have just been back in touch and they reckon on a bad earth, where do you start looking?? Another unit is being despatched but very reluctant to plug it in until I know everything is 100% as they will not swop it again under warranty!
hi simon,i think its quite possible you have a bad earth,and in all honesty its probably more likely than the relay given that earthing problems are not uncommon.i,like pete,do not think the inertia switch is the likely culprit given the info youve supplied.youll need to find the earth terminal(s) on the ecu loom plug-sorry,cant help here,and first check for continuity then if thats ok id still check for the impedence in the cicuit if you can.luckily,your right next to the battery negative teminal with the ecu as this is of couse the best test point!id never run the car for any length of time without the correct type relays though,weve been having a good chat about this on the chim forum-see "fuel pump experience to share" currently still running on their first page,as ive just replied again!
griffrhysjones said:
Excellent point there mongoose, I have read on PH that there should be two metal ones, however I have one metal and one plastic, surely something as simple as this couldn't be the cause? The ECU company have just been back in touch and they reckon on a bad earth, where do you start looking?? Another unit is being despatched but very reluctant to plug it in until I know everything is 100% as they will not swop it again under warranty!
Opinion seems divided on the purpose of the metal relay over a 'standard' one. The metal relay apparently comprises an extra diode - some say to prevent battery discharge, others to prevent a back EMF. If the latter, the back EMF may be causing damage to delicate ECU circuitry. Either way, for the sake of £7 from a Bosch dealer, get the proper relay in.
As for earths, you have to get your spanners out and do them all! There's one in the driver's side front wheel arch (to diagonal chassis outrigger leg), one to the very front of the driver's side chassis rail OR to the anti-roll bar mount just above the front of the chassis rail, a minor one on the back of the passenger side cylinder head (git to get at, but it can be done) and an earth tag somewhere under the passenger side injector rail (I forget exactly where). I might have missed one - anyone? Clean them up (fine sand paper or similar), copper grease, put them back together and waxoyl.
If no joy, you'll have look further afield (loom, ECU connector, relay mounts, sensors etc - start by looking for dodgy/loose/dirty connections before relacing bits).
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