jordan_meakin Posted May 7, 2016 Share Posted May 7, 2016 Having problems with my Series III with a 2.25 petrol. At low revs and through hard acceleration, the engine is "spitting" or mis-firing. It has been off the road for quite some time as I have been doing various bits of work (including carb. rebuild). I have also replaced the ignition system to rule it out. I have done a compression test and it's reading around 9 bar across all cylinders. However, I have noticed that if I remove the leads from cylinders one and two whilst running, it does not cut out. However, from 3 and 4, it does. Hence the compression test - head gasket? There are no symptoms of head-gasket failure. Oil is clean, water is clean, no clouds of steam etc. Does anyone have any ideas? I am hoping I haven't done anything wrong on the carb... It runs quite well when on the road and revving harder just this annoying mis-fire that I would usually associate to dirty points, bad leads etc but, as I say - already ruled that out. Any help greatly appreciated! Quote Link to comment Share on other sites More sharing options...
lo-fi Posted May 8, 2016 Share Posted May 8, 2016 Was it running OK before it got laid up? Did the problem start after you rebuilt the carb and before you changed ignition? Quote Link to comment Share on other sites More sharing options...
deep Posted May 8, 2016 Share Posted May 8, 2016 It does sound like it's either running too lean or sucking air. It could be as simple as a vacuum connection not, um, connected on your manifold. Failing that, if the carb has been off and dry for some time, there could be a little corrosion in a jet. Quote Link to comment Share on other sites More sharing options...
Cornish Rattler Posted May 12, 2016 Share Posted May 12, 2016 Could be a faulty coil getting hot, had this on my s111 years ago driving from Manchester to Cornwall towing a caravan lookerly my bro was with us in his s11a so we got to the services and found a local motorist shop and bought a new coil fitted it and everything was ok again, hope you get it sorted Quote Link to comment Share on other sites More sharing options...
Peaklander Posted May 14, 2016 Share Posted May 14, 2016 The tiniest bit of dirt in the carb can provide these symptoms. If you think it might be that, use some carb cleaner and give every orifice a good spray. Quote Link to comment Share on other sites More sharing options...
jordan_meakin Posted May 14, 2016 Author Share Posted May 14, 2016 Hi all, Thanks for the replies. The problems occurred after it was laid up but has been off the road for a year hence suspecting ignition. As I've replaced all that again, I feel it rules it out... I have replaced all gaskets and lapped the carb faces to seal air leaks (that's why I did it) and replaced all jets etc. in the process. It was basically a process of dismantling and replacing like for like, cleaning along the way. I must say, carbs make me nervous because I don't really understand them! Do you think running badly on only some of the cylinders would be a symptom of carb problems? Bloody Zeniths!!! Appreciate any help as always. Quote Link to comment Share on other sites More sharing options...
deep Posted May 15, 2016 Share Posted May 15, 2016 Hmm, re-reading your first post, you've actually pin-pointed the problem to cylinders one and two. Highly unlikely you've put the leads on wrong but.... Also check the distributor cap for a crack (it could be invisible but you may see a trace of carbon). Another possibility is that some valves have got sticky. This was very common a few decades ago, if a vehicle sat for a bit. Whip the rocker cover off and check tappet settings but also tap each valve down with a soft hammer and see if it immediately bounces back. A sticky one is obvious because it makes a dull sound, not at all like the good valves. It would only take a slightly poor seat to give those symptoms. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted May 15, 2016 Share Posted May 15, 2016 Do you think running badly on only some of the cylinders would be a symptom of carb problems? Bloody Zeniths!!! I can't answer that definitively I'm afraid but I do know that after refurbing my S3 carb with new jets etc. I has a mis-fire which was caused by dirt that carb spray dissolved / removed. To isolate the problem to the cylinders could you exchange the leads from dist to plugs one by one from a "good" cylinder to a "bad" and secondly try swapping plugs in the same way? Quote Link to comment Share on other sites More sharing options...
jordan_meakin Posted May 29, 2016 Author Share Posted May 29, 2016 So, turns out it was a big hole in the servo causing massive vacuum leak. New servo too! Refurbished carb is letting it run beautifully. Quote Link to comment Share on other sites More sharing options...
deep Posted May 30, 2016 Share Posted May 30, 2016 Great news. So satisfying to have located the problem! (Also to know my first diagnosis was on the money, feeling smug for a change...) Quote Link to comment Share on other sites More sharing options...
Peaklander Posted May 30, 2016 Share Posted May 30, 2016 Good news and a good diagnosis Deep. Also thank you for coming back with a conclusion - these really make the threads useful. So often when searching for something on an internet thread it just stops... Quote Link to comment Share on other sites More sharing options...
jordan_meakin Posted May 31, 2016 Author Share Posted May 31, 2016 I think it's that blind assumption that a new part is okay, a trap that I have fallen in before! I did a lot of work all at once and it never crossed my mind that the servo would be the culprit despite noticing a very loud sucking! What a fool I suppose... Thanks all! Quote Link to comment Share on other sites More sharing options...
deep Posted May 31, 2016 Share Posted May 31, 2016 Good news and a good diagnosis Deep. Also thank you for coming back with a conclusion - these really make the threads useful. So often when searching for something on an internet thread it just stops... Ta - and excellent point about coming back with the conclusion. It's the real way we learn here! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.