14 replies to this topic

[lachlan1275gt]

Continuation from this post, please give it a read: https://www.theminif...under-throttle/

Turns out it was the coil of all things that caused the initial problem I think, replaced the distributor too. Compression test came back good, valve clearances checked / reset, carb float level set properly, jetting hasn't changed for ~5 years which it has been running for.

 

My mini now starts first try, and idles nicely, albeit with the timing not set properly (it is pretty close) as I changed the distributor just to make sure the problem did not originate from it. However I have the exact same symptoms with the old distributor.

 

I can go for a small drive, so long as I keep the revs up OR I advance the timing a bit. However if I turn the engine off, then try to restart it immediately, it will start, but not very easily, then if I wait another 10 seconds or so, it absolutely WILL NOT fire. It doesn't matter if I crank it over with no throttle, lightly feathering the throttle, or choke, the result is always the same. There is spark on each plug when it will not start, and fuel is definitely getting in as the plugs get wet and I smell fuel.

 

To clarify, I can start it easily, but after running for a bit, it will not restart, but if I leave it for ~1 hour it will start again. Ideas? I can't think of anything that would be time related.

Edited by lachlan1275gt, 30 November 2022 - 11:18 PM.

[timmy850]

Which coil did you buy and are you using a ballast setup? It sounds like possibly an overheating problem if it works again after an hour. If you have the wrong coil for your setup it might be over charging

[Earwax]

Hi Lachlan ,,   As Timmy suggests - sounds like overheating. Incorrect coil is one culprit  as too is retarded timing.   If you have a multimeter check the resistance of the coil    and I would replace the condensor 

 

- Using your description  - of raise revs a bit or advance timing- to take it for a run - again if you can, you need to verify the timing is okay - running retarded at some revs will quickly add lots of heat to the engine bay  

[lachlan1275gt]

Lucas sport 12v coil

https://www.classicc...=20533043429464

I assume I am not running a ballast, however I have no idea why I am assuming this. Its a 1980 1275gt with the original wiring so whatever is stock on that?

[timmy850]

Lucas sport 12v coil
https://www.classicc...=20533043429464
I assume I am not running a ballast, however I have no idea why I am assuming this. Its a 1980 1275gt with the original wiring so whatever is stock on that?

I believe a 1980 should have a ballast. You can check by seeing what the voltage is like at the positive side of the coil

See here:
https://blog.simonbb...ance-and-coils/

But a 3 ohm coil + ballast will mean it’s under charged and not over charged

[lachlan1275gt]

Oh wow didn't even consider that it might be ballasted, I was going off the fact that it is pre 1984 it is likely non ballast from this :  https://www.theminif...ignition-check/

I'll have a look tonight, I still have the old coil so I'll check that too.

Edited by lachlan1275gt, 01 December 2022 - 12:52 AM.

[timmy850]

Sorry I don’t see many later minis so 1984 is probably the change point

No harm in checking though as minis tend to have a few modifications over the years

[lachlan1275gt]

Confirmed it is non ballast so I assume this means I have the correct coil?

12v at the coil on ignition, and negligible resistance on the wire from coil to the end where it meets the fuse box.

So likely the timing is just extremely retarded, although the static timing is set correctly, I didn't think the timing "starting point" could be so out that it would cause overheating problems but I'll find out once I time it properly.

[richmondclassicsnorthwales]

Do you have enough oil in your carburettor dashpot ? 

[mini13]

possible over fueling at idle due to fuel pushing past the float valve?? could even be intermitant.

do you have an electric pump or mechanical, if electric what PSI pump, got a fuel filter fitted?
 

if the plugs have been wet I would change them as a matter of course.

[lachlan1275gt]

Do you have enough oil in your carburettor dashpot ? 

I'm running a Weber DCOE, don't think it has dashpot oil?

[lachlan1275gt]

possible over fueling at idle due to fuel pushing past the float valve?? could even be intermitant.

do you have an electric pump or mechanical, if electric what PSI pump, got a fuel filter fitted?
 

if the plugs have been wet I would change them as a matter of course.

Yes very well could be an overfuelling problem I think, after some mucking around last night I found that the choke causes it it IMMEDIATELY cut out at idle.

 

Yep running an electronic fuel pump, no idea what psi I'll have a look tonight. And yep I have a fuel filter fitted.

 

Replaced the plugs yesterday in case they were fouled at some point.

 

I am going to fit another carb to it which I know for sure is jetted properly and has no issues as it came off this engine a couple months ago.

Edited by lachlan1275gt, 01 December 2022 - 09:40 PM.

[lachlan1275gt]

Fit a known working carb and all my problems magically disappeared. So will set my timing and get it running nicely then try again with the old carb.

[mini13]

I'd have the top of and check the float valve out as a meter or course, Also worth looking at the cold start ( choke ) system, Its been many years since Ive looked at a DCOE, but I seem to remember that the choke system can stick and dribble ( two sliding valves controlled by cams and a lever) . there is in fact a cold start delete kit for racers.

https://lotuselan.ne...=36203&start=15

 

[lachlan1275gt]

Forgot to report back;

 

Problem was the float bowl level, which I had set the level with the fuel pump/ignition OFF. Which meant the fuel had drained the slightest amount so I over corrected when setting the float bowl level, leading to a incredibly rich mixture at idle.

 

In summary the causes, in order;

Old coil failing,

Slightly loose grub screw on carb venturi,

Foolishly adjusting the float bowl level (even though it had been fine the last 5 years)

 

Thanks very much to everyone who helped, this has been a great introduction to the mini community, and since my first post/first mini in 2021 I am now hooked on Minis for better or worse.