Orange Posted August 3 Share Posted August 3 Just been out for a drive in the Caterham and it has developed a misfire, it got progressively worse and revs hunt on tickover as it tries to keep running. i have noticed that the battery is at circa 10.8v and does not appear to be charging when revved. If I connect 12v power to it, it runs better. What are thoughts battery or alternator? How do I check health of both? If alternator what is it from for a replacement? Just having a beer as relieved to have limped it home? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 1 Has it been drowned? Or has any work been one on it recently? 2 What battery does it have? If appropriate check fluid levels and top up. 3 Measure the voltage across the battery at rest, the minimum during cranking, and at 3,000 rpm. 4 Check the alternator belt and the accessible mechanics of the alternator. 5 Inspect all of the relevant circuits and connections, including a good wiggle. (I'll comment on what you can do to fix alternators once we know what's wrong.) Jonathan Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 Yes twice. I have driven through two biblical storms in the last 4weeks! My suspicion it dead alternator (I have already had to replace the oil pressure sender due to water damage and was out enjoying this working!) Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 3 minutes ago, Orange said: Yes twice. I have driven through two biblical storms in the last 4weeks! I don't think that drowning the electric is a common problem on K series, but have a look at the coil(s), HT cables and the the tops of the plugs. Dry it all out. Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 3 minutes ago, Orange said: I have already had to replace the oil pressure sender due to water damage and was out enjoying this working! Check any wiring near where you were working. Jonathan Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 Many thanks, I was checking wiring when I noticed the battery voltage. HT leads I assume would not affect battery charging…. i did notice a very slight misfire after the first soaking on a subsequent drive and have actually replaced spark plugs and fuel filter to try and solve. Todays misfire is very noticeable and not intermittent. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 2 minutes ago, Orange said: HT leads I assume would not affect battery charging…. We're going to measure that directly in step 3.... : - ) Jonathan Link to comment Share on other sites More sharing options...
Roadsport06 Posted August 3 Share Posted August 3 Have you compared a voltage for the battery in current state, car running, and cranking? Battery - if it is a wet battery, have you checked the fluid levels in each cell? Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 Yes checked levels in battery. 11.8 when back after run and not changing when revved. Dips slightly when cranking. i have put it on charge to see what it does. This is why i am not sure if it is battery or alternator. Battery is not increasing in voltage when revved. Is it battery not accepting charge or alternator not providing charge? Could still be wiring but waiting to have a look after it has cooled down. Link to comment Share on other sites More sharing options...
Wrightpayne Posted August 3 Share Posted August 3 I’d check the plug holes to ensure dry - they have been known to fill with water! That said I think you’ve narrowed down the culprits! 1 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 44 minutes ago, Orange said: Yes checked levels in battery. 11.8 when back after run and not changing when revved. Dips slightly when cranking. i have put it on charge to see what it does. This is why i am not sure if it is battery or alternator. Battery is not increasing in voltage when revved. Is it battery not accepting charge or alternator not providing charge? Could still be wiring but waiting to have a look after it has cooled down. I'd expect that to be caused by the charging system rather than the battery itself. ... How does the red charging light behave? Does it come on with the ignition? Does it go off when the engine starts? Check all of the relevant wiring and connections, including the engine earths. Check the tension and condition of the alternator belt. Check the mechanicals of the alternator including friction and play. ... If it turns out to be a fault within the alternator it's often possible to have it repaired. This can be cheaper than a new one, and you know that the mount and the terminals will fit. Jonathan Link to comment Share on other sites More sharing options...
Area Representative Paul Richards Posted August 3 Area Representative Share Posted August 3 If volts don’t increase when engine revved I suspect alternator. By the way. Oil pressure sender goes faulty as water and muck get in it. If you have fitted a new one seal the gap around the spade terminal with silicone to prevent ingress. It will increase the life. Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 Many thanks, yes sealed this one - last one lasted less than a year! Battery is at 11.8v at rest - slight increase when revved (0.2v increase) When I measure the output voltage at the alternator it is 12.8v at 2k revs - does that sound right? I am suspecting another duff banner battery….thoughts? Link to comment Share on other sites More sharing options...
PlastererPete Posted August 3 Share Posted August 3 Whats the output alternator output voltage at 3krpm? Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 I will have to measure that tomorrow (my son has gone to bed now…) what should it be? Link to comment Share on other sites More sharing options...
PlastererPete Posted August 3 Share Posted August 3 9 minutes ago, Orange said: I will have to measure that tomorrow (my son has gone to bed now…) what should it be? Should be around 13.5-14.4v if the alternator is giving sufficient output to charge. Side note, is the alternator clean/dry after being out in the bad weather? Link to comment Share on other sites More sharing options...
Orange Posted August 3 Author Share Posted August 3 Yes car (and alternator)is now completely dry. Many thanks for the info / I didn’t think to rev it higher to see if the voltage went up! Link to comment Share on other sites More sharing options...
anthonym Posted August 3 Share Posted August 3 sounds like the alternator to me Link to comment Share on other sites More sharing options...
anthonym Posted August 3 Share Posted August 3 and if it is don't go too far from home cos the car is running only on what remains in the battery, so without lights maybe an hour (highly variable) and the battery voltage will get less and less until at 7 volts everything dies. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 3 Member Share Posted August 3 7 minutes ago, Orange said: Many thanks for the info / I didn’t think to rev it higher to see if the voltage went up! 4 hours ago, Jonathan Kay said: 3 Measure the voltage across the battery at rest, the minimum during cranking, and at 3,000 rpm. These three measurements give a lot of information very quickly. Jonathan Link to comment Share on other sites More sharing options...
anthonym Posted August 3 Share Posted August 3 (edited) strikes me you could switch all the lights on, main beam, with the engine running, if it dies you know the alty is goosed (or disconnected). Last time this happened to me all tests showed the alty was knackered. Ordered new one. During replacement the mechanic (somewhere deep in remote France) found the apparently "good on inspection" B connection (alty to battery wire) was completely disintegrated (an old car) - and the alty worked perfectly. Expensive! How long to die? 20 minutes? Or check the reducing battery voltage, no charge coming in. Edited August 4 by anthonym added "alty to battery wire" Link to comment Share on other sites More sharing options...
anthonym Posted August 3 Share Posted August 3 (edited) and if it is charging has the water blown the diode(s) in the alternator? One can test for this but I forget how. Do we have a wiki that explains? a blown diode means you can suffer parisitic drain where the alty sucks the charge out of the battery - it does this when the engine is off. been there, done all this Edited August 3 by anthonym 1 Link to comment Share on other sites More sharing options...
anthonym Posted August 3 Share Posted August 3 (edited) Quote Quote been there, done all this well, in my test I was attempting to get over an Alp and half way up it at 7 volts everything stopped. So that was a pleasant night in Aosta while being rescued by s h m b o rescue service. one time my alty failed and I was outside the gates of the factory in Italy that made it.. closed of course. Frustrating. Edited August 3 by anthonym Link to comment Share on other sites More sharing options...
Leadership Team Andrew 21 Edney Posted August 4 Leadership Team Share Posted August 4 Also worth checking the circuit from the alternator to the battery. Had the annoying situation (many years ago) of the 21 cutting out whilst driving due to a pinched wire somewhere finally giving up on passing a current. Roadside assistance fitted a "temporary" replacement which was still doing sterling work when I sold the car... 1 Link to comment Share on other sites More sharing options...
Orange Posted August 4 Author Share Posted August 4 Had a chance to do a few more checks. I only see 12.7v at the alternator at 2, 3 & 4k revs. Battery is at 12.6v at rest. it appears that the alternator is having minimal effect so guess this is what needs replacement (assuming there is nothing else beyond this causing the misfire) Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now