17 replies to this topic

[jacobtomos]

Hi all,

1988 mini randomly refused to start for me last week. Turns over strong, wouldnt fire. After usual fuel down carb/points checks etc I changed the plugs and it turned over straight away. The old plugs, though, were completely coked up- black, dry.

Drove to MOT today, then it started the same games! Bump started, got it back, spark plugs are black again. I’ve tried cleaning them up and it sounds like it wants to fire up but won’t. Turns over fast.

I’ve not had her long- it’s a ballasted system and I think the coil is non-ballasted. Would that have the impact of a weak spark?

[lsto]

If the coil is wrong it will make it more difficult to start, to be fair if your plugs are fouling then your carb is probably a bit rich too.
Measure the coil and go from there. Might be a good opportunity to go through the ignition system and make sure everything is in good condition.

[jacobtomos]

Cheers. It’s very hit and miss which is frustrating. I got it running earlier a few times after cleaning the sparks and now it’s stopped again. I’ve turned the HS4 nut up a few turns but I think it’s the weak spark and fouling that is causing the poor starting, and badly set up carb causing the fouling. I’ll try again in the morning with some fresh plugs and see how it goes. It stinks of petrol. Hopefully leaning out the mix might help.

[Chris1275gt]

I’d check the carburettor over first sounds like it’s letting far too much fuel in which with a very rich mixture will foul the plugs in no time at all causing the spark to dissipate and produce a very weak spark or no spark at all. when you’ve changed to the clean plugs it’s sparking and firing ok so I don’t think starting with the electrics is the way to go.

[Steam]

Start with the basics on the carb. Turn the mixture nut up until it stops then back down one and a half full turns which will give you a good base mixture setting. Check or even replace the air filter and make sure there is the correct oil level in the carb dashpot. While you have the filter off make sure the carb pistons lifts freely ( although the oil should give some resistance) and also drops freely.
From thara you can start with the ignition knowing that the moxture is somewhere near. A strong blue sparh from each plug is requited for good running.

[jacobtomos]

So, started on first turn of the key this morning… I don’t understand why it is so intermittent. Thanks for the carb advice. I’ve leaned it right out. I think the carb might need a refurb, the choke does very little- the linkage is wonky and doesn’t move the jet down. I can do it manually with my finger but it is stiff.

[andyapanel]

Intermittent problems would tend to suggest the coil. It would have cooled down overnight giving you a nice spark this morning.
Have you measured the resistances yet?

Hope you get it sorted soon

[sonscar]

The float could be flooding the carb,worth a look.Steve..

[jacobtomos]

Cheers, I’ll check the carb float then. I’ve checked the resistance and the current coil is giving around 2.8 ohm so I presume standard. I’ll get a ballasted one fitted and see how it goes.

[68+86auto]

Cheers, I’ll check the carb float then. I’ve checked the resistance and the current coil is giving around 2.8 ohm so I presume standard. I’ll get a ballasted one fitted and see how it goes.

 

Just make sure that the resistive wire hasn't been bypassed.

Edited by 68+86auto, 02 September 2024 - 01:35 AM.

[jacobtomos]

I am worried about that. Is there a check I can do? The pink/white goes back into the loom and I assume somewhere connects back with the white as that is what is at fuse 1.

[68+86auto]

I am worried about that. Is there a check I can do? The pink/white goes back into the loom and I assume somewhere connects back with the white as that is what is at fuse 1.

 

Fire it up and read the voltage between the coil positive and the engine/body earth. 

[jacobtomos]

Okay, so a few updates on this. New coil on (and now has MOT! ) but it only fires up once a day...

 

I get one journey out of each set of spark plugs. MOT station is about 5 miles away, so I got it there and then they needed to bump it to get it in. Also, once it was going for a few miles it just bogged down under load. Great at higher RPM. 

 

I now know the coil is right and it is starting better (that once per day!). I did have a thought. When I first bought her the previous owner had removed the engine steady for whatever reason so every acceleration led to a clunk. Looking at the jet, it seems bent to me? There is also a mark on the bulkhead which seems to have been caused by the jet striking it.

 

Could the jet have been damaged, which is in turn causing the problems I'm seeing? Please can someone look at the pics and let me know your thoughts. If it is, what options do I have? New HS4?

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[sonscar]

That does look badly bent and is likely sticking open when the choke is used leading to excessive richness.Steve..

[jacobtomos]

Thanks for confirming- can I bend it back? Or is it a new carb?