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'Old' model MFU Rover reference


Pierre Gillet

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My mate Serge is still struggling with a Seven whose engine does not cut off when the ignition switch is turned off.

He is now suspecting the MFU which is of the 'old model' (according to the excellent angus&tessa site), car is 1997.

He would like to order one from Rover. They need a reference.

There is no apparent tag on his MFU.

 

Can someone help ?

 

 

 

 

 

 

Edited by - Pierre Gillet on 24 May 2005 21:28:41

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Hi Pierre

 

If Serge wants a fix for the run-on I have one that I'm going to fit once I get my car back from CM. It just involves powering each of the two fan motors via schottky diodes. This blocks the back EMF of the motors from driving the ECU when you turn off. To be on the safe side I'm going to double up on the diode feeding the cooling fan so one diode could fail and still leave you with a working fan.

 

Colin

 

Edited by - Colin Mill on 25 May 2005 20:38:00

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More seriously though - do you know about how long the run-on lasts? Also does Serge have any non-standard bits of electrical stuff fitted to the car?

 

It would be interesting to connect an LED in series with about a 1k resistor across the switched side of the ignition and look if it goes out sharply when you turn off or goes out gradually.

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Colin your last proposal is troubling since there actually was a diode on one of the white leads (switched side of the ignition button) probably inserted by the former owner. Serge did not insert it again when he installed a on/off helicopter style ignition switch and a starter push button.

here

 

Pierre

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Sorry Pierre - I should have looked at the wiring diagram closer. There is an unswitched feed to the ECU (via fuse 14) so I guess this provides the injector and ignition power. That explains part of it. I'll look a bit more at the diagrams and get back to you
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Yes, that diode looks exactly the sort of thing. Perhaps its worth dropping it back in. If the ECU relay is really low current then perhaps a decoupling capacitor on the input side of some bit of electronics on the car could hold the relay in for long enough to cause the problem. At a guess the overun does not happen with the headlights on - am I right?

 

 

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The Rover reference for a 1600 K 1997 MFU is YWB 10022.

 

With a a new ECU/Immobilizer and a new MFU the problem is still there: the engine cuts off in 2 mn of time with his old MFU and 4 mn with the new one.

Serge has still not bought the LED and resistor but plans to do it presently.

 

Hi Colin, the overun does happen with the headlights on *confused*

Pierre

 

 

 

Edited by - Pierre Gillet on 26 May 2005 20:41:43

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Ok - its certainly a tough one. That's one hell of an over-run time as well!

 

The only additional info I have is from a Rover circuit diagram. When the MEMS ECU is fitted to a Rover Metro the feed to ECU plug 2 pin 80 seems to be switched by a relay. In the Caterham this feed is unswitched. So on the Metro the relay does the equivalent of pulling fuse number 14 (which I seem to recall you said stopped the over-run)

 

Colin

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Serge finally had his car looked after by the Rover garage of Chambery. Their electrician solved the problem. At this time we still do not know how, but we keep you posted as soon as possible.

Many thanks for your help guys *thumbup* *thumbup* *thumbup*

Cheers,

 

Pierre

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OK Serge has now the explanation from the Rover electrician:

It seems that a small loss of current on the windscreen electric heating was feeding the ECU through the positive lead after ignition under a 2 Volt tension.So the ECU was not getting the signal that ignition was off when the ignition switch was turned off and was not triggering the main relay which was quite normally staying closed until consumption of this current which would take about 2 minutes.

The first owner had used a diode to avoid the 2 V current feeding the ECU.

Hope it is clear *confused*

My question is : how can a resistor (the windscreen electric heater) accumulate current ?

 

 

Pierre

 

Edited by - Pierre Gillet on 30 May 2005 20:56:54

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