AndrewGP Posted July 20, 2014 Share Posted July 20, 2014 Went out for a blat this morning and half way round, the RPM gauge started to get very erratic, swinging randomly between 0 and full scale deflection. Associated with this was the speedo needle started swinging about (but not as much as the RPM) and there was a pronounced misfire, ie the car got quite juddery and wouldn't pull cleanly. I managed to limp the car home and it's now sat looking guilty on the drive 😬 I've checked the wiring on the back of the gauge but a quick look through the archives suggests it could be the crank position sensor. Is there any way to test this out? Anything else I should be looking at? On a separate note (as I think it's unrelated) it's recently started to pop and bang on the over-run when before it never did - should I look at changing the TPS? Link to comment Share on other sites More sharing options...
revilla Posted July 20, 2014 Share Posted July 20, 2014 Very quick thought as I'm just about to go out ... I can't see Crank Pos Sensor affecting the speedo. Sounds more like a supply/earth problem. I'd be checking the wiring again. Measure the voltage between the earth connection at one of the gauges and the battery negative. If you can get it misbehave, measure while it's doing it. Should be 0 volts or something very very small. Link to comment Share on other sites More sharing options...
revilla Posted July 20, 2014 Share Posted July 20, 2014 Check your battery leads and the earths to the engine and from engine to body are secure. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 20, 2014 Member Share Posted July 20, 2014 What sort of ignition and ECU? + Check earths for block and ECU and instruments and similar. Any recent work or modifications? Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 20, 2014 Member Share Posted July 20, 2014 Morning, Andrew. Jonathan Link to comment Share on other sites More sharing options...
AndrewGP Posted July 20, 2014 Author Share Posted July 20, 2014 Hi Andrew, OK will do. BTW sent you an email ref K-Click last week, did you get it at all? Morning Jonathan, car is EU3 and standard R300 MBE unit, remapped by Northampton Motorsport earlier this year. I did recently fit a relay to bypass the ignition relay in the MFRU, however I did notice the RPM gauge flickering the blat before I fitted it. It was only a momentary thing though and I dismissed it at the time. However, I'll check it along with the earths. We have family over very soon, so I'll report back this afternoon. Link to comment Share on other sites More sharing options...
shn7 Posted July 20, 2014 Share Posted July 20, 2014 Alternator not charging? Symptoms suggest reducing voltage in the system. Link to comment Share on other sites More sharing options...
elie boone Posted July 20, 2014 Share Posted July 20, 2014 I would also check the wires that go to the coil. Link to comment Share on other sites More sharing options...
revilla Posted July 20, 2014 Share Posted July 20, 2014 Morning , Jonathan 😬 @grenpayne - Yes, I did get it, very sorry I haven't gort back to you yet I'm running a bit behind with my emails. Had a hectic week at work plus a hole in my engine block that required an engine swap Will get back to you a.s.a.p. Link to comment Share on other sites More sharing options...
AndrewGP Posted July 22, 2014 Author Share Posted July 22, 2014 Update I've checked all the chassis earths both visually and with a meter and they're all fine, I had cleaned them all up over the winter with emery paper so I thought they'd still be ok. The alternator is charging the battery OK and the voltage drop from the rpm gauge negative and the battery negative was also zero. So I've now taken the primaries off the car and had a look at the starter and alternator wiring and it's all in a pretty bad state to be honest! So the next job is to make some up new wiring. I've also ordered a new SND1250 solenoid from Wood Auto and fingers crossed this should sort the problem of the starting and the flickering rev counter. I'll report back when I've got it all back together! Edited by - grenpayne on 22 Jul 2014 16:39:48 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted July 22, 2014 Share Posted July 22, 2014 Out of stock ..... maybe you had the last one ? Link to comment Share on other sites More sharing options...
AndrewGP Posted July 22, 2014 Author Share Posted July 22, 2014 I actually phoned them up on the off chance the website wasn't correct, it wasn't and they had one in stock 😬 Link to comment Share on other sites More sharing options...
sjmmarsh Posted July 23, 2014 Share Posted July 23, 2014 If you have a push button starter, check the knurled ring holding it to the dash hasn't come undone and is resting on the terminals. I had this happen on a Trackday and the intermittent momentary engagement of the starter motor gave symptoms very similar to what you describe. Steve Link to comment Share on other sites More sharing options...
Guest Posted July 23, 2014 Share Posted July 23, 2014 Andrew I had these exact same symptoms on mine the other week. I was following Geoff and each bump produced a misfire and the erratic rev counter behaviour. I had recently replaced the starter relay in a bid to resolve my K click and this was the problem - it was slightly loose in its fitting and each bump caused it to lose contact momentarily. Removal and refitting the relay properly in its shoe solved the issue. I hadnt appreciated that the starter relay would be part of the ignition circuit whilst running. Tim Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 23, 2014 Member Share Posted July 23, 2014 *arrowup*Hmmm.... I wonder why that happened: * Taking the feed to the ignition to earth (which should blow a fuse if there is one) * Breaking the feed to the ignition * Breaking a common earth * Something else? Is that feed fused? Was that a standard starter relay or a modification eg following the starter click syndrome? Thanks Jonathan Link to comment Share on other sites More sharing options...
Guest Posted July 23, 2014 Share Posted July 23, 2014 Another thought - maybe its being out for a Blat with Geoff causing some kind of weird voodo hoodo? Link to comment Share on other sites More sharing options...
AndrewGP Posted July 23, 2014 Author Share Posted July 23, 2014 Thanks Tim Whilst my relay mod is sound and the relay nice and tight in the housing, I may have solved the erratic rpm issue. The solenoid arrived today (great service from Woods Auto) and I fitted it this afternoon to the starter and put the whole lot back on the car. Whilst I was refitting the solenoid wiring, I discovered the nyloc holding the feed wire on the alternator was loose It was quite obvious that the ring terminal would have been able to vibrate quite a bit, making and breaking the connection. Would this likely be the cause of the flickering rpm needle and associated misfire? On the separate K Click issue, I'll finish the job tomorrow and take the car out for a blat to see if this has been solved, but with a new relay, a new solenoid and new wiring I bloomin' hope so 😬 Steve, many thanks, I've checked the knurled ring on the starter button and it's nice and tight. Never heard that one before so very useful to know Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 23, 2014 Member Share Posted July 23, 2014 Quoting grenpayne: Whilst I was refitting the solenoid wiring, I discovered the nyloc holding the feed wire on the alternator was loose... It was quite obvious that the ring terminal would have been able to vibrate quite a bit, making and breaking the connection. Would this likely be the cause of the flickering rpm needle and associated misfire?I suppose it's possible and I'll put my money on the problem disappearing. Jonathan Link to comment Share on other sites More sharing options...
revilla Posted July 23, 2014 Share Posted July 23, 2014 Yes I can see that playing havoc with the voltage regulation. Link to comment Share on other sites More sharing options...
AndrewGP Posted July 25, 2014 Author Share Posted July 25, 2014 Well I took the car the very long way to work and back this morning and I'm glad to say it's all fixed 😬 The misfire and flickering rpm gauge has gone and must have been the loose alternator lead. The new relay, leads and solenoid have also finally sorted the K Click out. I must have switched the car on and off at least 20 times whilst it was red hot and it started on the button every time. No more sitting in petrol stations looking like a berk 😬 I'd also like to say a massive thanks to Andrew (Revilla) for taking lots of time over the last few months to try to work out what's going on with my MFRU wiring and ultimately help me sort out the K Click issue, it's much appreciated I did find something you may find useful in the future so will drop you an email later on too. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 25, 2014 Member Share Posted July 25, 2014 :-) Jonathan Link to comment Share on other sites More sharing options...
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