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#445420 - 27/04/17 02:41 PM Rev Counter behaviour on a Roadster 100
Frank 4x4 Offline
Green & Grown Up
Talk Morgan Addict

Registered: 10/05/09
Posts: 3606
Loc: Hill Head, Hampshire, Uk
Can anyone help please with this question from a R100 Register Member living on the South of France. Or have you had a similar experience with your Morgan and what was your solution?
Best Wishes
Frank thumbs

"When starting cold (and after about 20 seconds) stationary and sometimes when hot in stalled traffic the rev counter starts to go all over the place….to the point of going up to 3000 and down to zero (stalling).

Once warm it goes fine (other than sometimes in stalled traffic).

The  Lambda sensors have been changed, as has the MAF and plugs but it appears the sensors are not always talking to the ECU.

I am at the point of thinking that I may have to send the ECU  back to Morgan to be reprogrammed. Have you heard of any similar stories?"
_________________________
http://franks4x4-solograndetour.blogspot.co.uk/
Combat Stress-http://www.justgiving.com/Roadster100

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#445423 - 27/04/17 03:01 PM Re: Rev Counter behaviour on a Roadster 100 [Re: Frank 4x4]
Spanner Juggler Offline

Talk Morgan Expert

Registered: 31/08/13
Posts: 2466
Loc: Leicester
Frank

I am unclear, can you confirm its just the rev counter (Tachometer) that is going up and down and not the revs of the car?

If its just the Tachometer its more likely a connection or sensor than the ECU. To be honest, and despite the blame they get, ECU's rarely fail, what does fail all the time is the input sensors and output actuators and more commonly the connections and earths in the wiring harness.

I remember our warranty test department at Volvo, less than 2% of returned ECU's actually had a problem and in many cases where dealers claimed fitting a new one cured the fault and argued that proved an ECU fault further testing proved it was the simple unplug and re-plug of the main multi pin connector that cured a bad connection. many input signals are very low voltage and it takes very little to corrupt them.
_________________________
BR Colin
Who used to be a Spanner Juggler

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#445427 - 27/04/17 04:01 PM Re: Rev Counter behaviour on a Roadster 100 [Re: Frank 4x4]
MOG 615 Offline
Has a lot to Say!

Registered: 24/09/14
Posts: 1253
Loc: London
Frank

What is the condition of your battery , or is there an electrical connection somewhere that could be losing voltage (as per Colin's comments above a low voltage can trigger all sorts of weird and wonderful behaviour)

I had this happen on my tin top , when the battery was getting very low in charge, on turning the key to start, nothing from the starter, but both rev counter and speedo needles did a complete swing over to "max" , and back again , and I lost of all of the data like radio pre-sets, trip miles, average fuel consumption readings etc. I had to resort to a bump start (not easy on flat ground with a diesel!) which started the car but the readouts were still way out for some miles before everything settled down again.
_________________________
Andy G
1999 +8 , Indigo Blue.
Ex-John McKecknie/Mike Duncan 1955 +4 racer.

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#445440 - 27/04/17 05:12 PM Re: Rev Counter behaviour on a Roadster 100 [Re: MOG 615]
Gambalunga Offline

Member of the Inner Circle

Registered: 03/09/11
Posts: 10512
Loc: Mandello del Lario, Lake Como,...
Originally Posted By MOG 615
as per Colin's comments above a low voltage can trigger all sorts of weird and wonderful behaviour

I don't think it would be low battery voltage when the car is actually running however, as you and Colin have both mentioned low input voltages to stepping motor instruments can cause the strangest behaviour. I too have resolved a problem with a motorcycle ECU by unplugging and replugging it. As Colin has said I would bet that there is a sensor or a connection problem. If the car is not actually stalling (as I read it it is only the tacho that is doing weird things) I would bet it is a connection problem. Mind you it could be a problem inside the instrument itself.
_________________________
Peter


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#445566 - 28/04/17 09:57 AM Re: Rev Counter behaviour on a Roadster 100 [Re: Gambalunga]
Frank 4x4 Offline
Green & Grown Up
Talk Morgan Addict

Registered: 10/05/09
Posts: 3606
Loc: Hill Head, Hampshire, Uk
A Big Thank You to all for the advice so far. thumbs

It is not my car, so I will pass on the information to the South of France where dealerships are apparently rare and hopefully it will lead our Roadster owner to the solution.

If I get any comments back I will add them here later.

Frank
_________________________
http://franks4x4-solograndetour.blogspot.co.uk/
Combat Stress-http://www.justgiving.com/Roadster100

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#445750 - 29/04/17 07:22 AM Re: Rev Counter behaviour on a Roadster 100 [Re: Frank 4x4]
AndyR Offline
L - Learner Plates On

Registered: 30/09/16
Posts: 228
Loc: Nr Preston, UK
Recently I've noticed similar behaviour on both my speedo and rev counter. The circuit board has just been changed by my dealer.

Could there be a connection?
_________________________
Andy

2011, 4/4, 2.0, 75th Anniversary
2016, VW Polo GTI
2012, BMW 520d Touring

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#445754 - 29/04/17 07:52 AM Re: Rev Counter behaviour on a Roadster 100 [Re: AndyR]
Budster Offline

Talk Morgan Sage

Registered: 07/08/11
Posts: 6198
Loc: Devon

I not sure if the Roadsters have a similar set up, but my 4/4 has an Instrument Control Module behind the dash.
Any fault or connection issue there causes a range of strange behaviour from the instruments and warning lights.
_________________________
Bud
4/4 "Stanley"

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#445782 - 29/04/17 11:32 AM Re: Rev Counter behaviour on a Roadster 100 [Re: Spanner Juggler]
Frank 4x4 Offline
Green & Grown Up
Talk Morgan Addict

Registered: 10/05/09
Posts: 3606
Loc: Hill Head, Hampshire, Uk
Originally Posted By Spanner Juggler
Frank, I am unclear, can you confirm its just the rev counter (Tachometer) that is going up and down and not the revs of the car?


The Owner Ian responded to all of your kind your comments with:-

I can confirm that it is not a mechanical problem, nor a battery problem, nor a rev counter problem….the rev counter is correctly recording the engines wild fluctuations.


It is a running problem that happens when the engine is idling…either when starting up cold or when stuck in traffic.

The actual engine revs will sometimes rev up from 800 to 3000 then down to 800 and back and forth….sometimes the engine just starts to drop from 800 down to 300 and then up and down until eventually the engine stalls (after some death throes violent juddering!!!)

The disadvantage of living in my part of France is being 6 hours drive away from the nearest Morgan dealer and ending up having to use garage people who do not have experience of Morgans

Ian is now convinced that it must be an ECU problem.

Any other ideas welcome please?
Best Wishes,
Frank
_________________________
http://franks4x4-solograndetour.blogspot.co.uk/
Combat Stress-http://www.justgiving.com/Roadster100

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#445794 - 29/04/17 12:53 PM Re: Rev Counter behaviour on a Roadster 100 [Re: Frank 4x4]
John V6 Offline

Member of the Inner Circle

Registered: 21/07/07
Posts: 12631
Loc: Suffolk
Frank it sounds like the ECU or an inlet air leak.
_________________________
JohnV6
2006 Indigo Blue Roadster S1

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#445798 - 29/04/17 02:05 PM Re: Rev Counter behaviour on a Roadster 100 [Re: Frank 4x4]
B3MOG Offline

Just Getting Started

Registered: 05/02/13
Posts: 90
Loc: north yorkshire
Frank, it could be the idle control valve I had a similar problem on my plus 8 it is easy to remove and clean or replace. I actually ran mine for sometime with the valve removed and the pipes blanked. It started and ran fine and ticked over at 800rpm.

David Byrne

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