Running rich but stuttering (and stinks!)

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PhilipW1039
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Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

To all you old timers who really know what you're doing, I wonder if I could ask for your help please? I'm a beginner and on a VERY steep learning curve so although I've read a lot, I don't know what I don't know.

I bought my '68 traveller 3 weeks ago. Ran fine, but rich (black exhaust and plugs). The head showed signs of an oil leak so I replaced the head gasket set and fitted the Grumpy stabiliser kit while there. Also new plugs, gapped to 25, and the head was skimmed 6 thou. I didn't adjust anything else and torqued all nuts as per manual.

Stupidly, I tried resetting the jet adjuster nut to the 12 flats undone, as per a post on here, in an effort to address the rich running. Since then, it stutters both at idle and at speed, even cruising at 40-50, though is worst at slower speeds in second. I've done the following:

- backed off the adjuster nut further, which has improved but not yet solved
- raised the piston lifting pin, which has no resistance for the first 6-8mm but then kills the engine
- fixed 70% of the blowing from the manifold-downpipe clamp. Waiting on cement for the rest.
- fitted new HT leads, distributor cap and rotor arm
- checked leads are 1,3,4,2, anti-clock as per post from BMCEcosse
- checked that the choke reduces revs when it goes back in, but not actually checked at the jet

The fact that it runs rich but absolutely stinks of petrol at the exhaust, is really confusing me. I'm reluctant to back the nut off any further as that seems wrong? I have an electronic ignition kit to fit, with the recommended sport coil, and am considering a carb service kit and replacement needle, but I'm working through replacing things with really only guesswork.

Any help would be gratefully received. Please, be gentle with me!!
Philip

Just gradually working things out...
don58van
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Re: Running rich but stuttering (and stinks!)

Post by don58van »

There will be plenty of experts along soon, but the best advice I can give you is to avoid changing many things at one time. It seems to be a fuel problem, so take cautious steps to identify the cause until you have solved the problem or eliminated the fuel system as the cause.
My 2 bobs worth.

Best wishes for sorting it out.
Don
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

I should also add that I've noticed a clicking since all the work I've done, which sounds like a ticking clock but louder (no, I don't have a clock in the car). I'm sure it wasn't there before.
Philip

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simmitc
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Re: Running rich but stuttering (and stinks!)

Post by simmitc »

The ticking sound is the fuel pump. When the ignition is switched on after a break, it is normal for the pump to tick once or twice and then stop. With the engine then started, the pump will tick regularly but not fast. The pump is controlled by pressure in the system that is caused by the float in the carb closing a valve and stopping the fuel flowing.

A continuous fast ticking suggests that there is (a) a leak if the engine is not running and/or (b) excessive consumption if the engine is running. It could be a fault in the pump, but that is very unlikely. The strong aroma of petrol is also an indication of (a) or (b).

When working on the fuel system, exercise great care - work in a well ventilated area and avoid naked flames, sparks and any other source of ignition as petrol fumes are explosive and there is a risk of fire :o

With the ignition on but the engine not running, inspect the flexible hose between the pump and the carburettor and also the carb itself. Is there any sign of a leak with petrol dripping? Modern petrol can attack old hoses and they crack and leak.

With the ignition off, remove the flexible fuel pipe from where it enters the carburettor float chamber and place in a container that is suitable for petrol. Switch on the ignition. The pump will run and petrol exit from the pipe. Place your thumb firmly over the end of the pipe. Does the pump stop running or carry on ticking? If it stops, then the pump is OK, and the problem is in the carb, if it carries on running then there is a problem with the pump. Switch off the ignition, reconnect the pipe and return any fuel collected to the tank. Check for leaks again. Report back on what you find.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Thanks ever so much for your reply, and to Don as well - some simple wisdom in what he said.

So, in specific response to those tests:

1. No leaks at all, definitely not.
2. With my finger over the end of the fuel tube the pump does still tick but only every 5 or 6 seconds.

No leaks after reconnection.

What I also tried was holding each HT lead to the block in turn. A couple sparked like mad but the other two could hardly emit a spark at all. Could it be that the carb is providing extra fuel but that it's not being burnt efficiently, hence the black exhaust pipe and petrol smell? Apologies if I'm going off on a tangent...
Philip

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oliver90owner
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Re: Running rich but stuttering (and stinks!)

Post by oliver90owner »

If the pump ticks any more often (shortly after being reconnected to the carb) than it did when you completely blocked off the fuel pipe you likely have a carb problem, where the fuel level in the float chamber is not being properly controlled.

The other likely fault is that of the cold start control not being released completely.

Re the sparks - what colour are they? A strong blue or a weak yellow? If weak, did you check the gap at the contact points? What colour/strength do you get from the king lead to earth?

Unless purchased from a seller of high quality parts, don’t fully trust any new parts you buy. A lot can be sub-standard.

Of course, the air filter may be causing some, but likely not all, your problem - if it is past its replacement time.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Thanks Oliver.

I ordered a service kit from EMS, which is where all my parts have come from. I've replaced the air filter already, as well as the plugs, leads, rotor arm and cap. I checked the points gap and that's 0.15.

The strength of spark varies depending on which lead I test but I don't know how to test the king lead - is that the one from the coil to the distributor?

I checked the float chamber and there is some dirt at the bottom. I then tried lifting the piston but no fuel came out of the jet, so I then tried running the engine while blanking off the air intake but it didn't make any difference.

The piston doesn't stick and the needle doesn't appear to be worn so, other than trying the accuspark ignition, which I have anyway, I'm thinking that servicing the carb would be a good shout?
Philip

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Myrtles Man
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Re: Running rich but stuttering (and stinks!)

Post by Myrtles Man »

PhilipW1039 wrote: Wed Apr 20, 2022 5:17 pm I checked the points gap and that's 0.15.



Mmm, I do hope you meant to write 0.015.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

I knew somebody would pick me up on that! Yes, 0.015 Myrtles :D
Philip

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Dogsdad
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Re: Running rich but stuttering (and stinks!)

Post by Dogsdad »

“Backing off” the adjuster nut ?
Do you mean lowering the jet?
If you do this is richening the mixture making things worse.
R.M.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Yes, I know, but the leaner I make it the worse the stuttering becomes. Making it richer improves the running but, like I said, this is why I'm reductant to back it off further. Or, as you rightly said, lower the jet.

My baseline if you like, was the 12 flats from the highest point but at this level, the stuttering is awful and almost undriveable. Even though that is theoretically the "correct" setting.

I really need some other suggestions, or somebody who knows better then I to say "yes, I'd take the carb apart and service it". In the absence of any better ideas that's what I'll have to do anyway.
Philip

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kevin s
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Re: Running rich but stuttering (and stinks!)

Post by kevin s »

I'd start with making sure the needle is set at the right height in the piston checking the float level and fitting a new jet, these are about all that controls the fueling in an SU.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Thanks Kevin, I'll try those things and see what gives. I'm nearly at the point of giving it to a classic car mechanic but I really don't want to give up!

Really appreciate the input, ta.
Philip

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oliver90owner
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Re: Running rich but stuttering (and stinks!)

Post by oliver90owner »

PhilipW1039 wrote: Wed Apr 20, 2022 5:50 pm I knew somebody would pick me up on that! Yes, 0.015 Myrtles :D
I hope you were quoting Imperial units, there!I have a couple of imperial feeler gauge sets somewhere but usually use a metric set.🙂
kennatt
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Re: Running rich but stuttering (and stinks!)

Post by kennatt »

have you checked that there is oil (Light oil) in the dash pot on the carb,To check unscrew the plunger pull it up and then push it back in there should be a fair amount of resistance, if none then add oil 3 in 1.If the piston is allowed to fly about there is no control on the position of the needle and jet and can cause over fuelling and rough running.
Regards the lifting pin,lift till you feel resistance then just a tad more,if the engine stops instantly as you describe that indicates too weak. But the above could be your problem.
good luck
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Cheers Kennatt, I only wish it were that simple. That was one of the first things I checked. Good shout though - it's easy to forget the simple stuff.

And Oliver, good point. Now you're making me question myself!! I'll double check my gauges but I'm sure I was using the Imperial measurement.
Philip

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PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

Right, solved it! Thanks to all of you for your ideas but a local old-school mechanic asked if I'd reset the valve clearances when I replaced the head etc, which I didn't! Schoolboy error, but as I said you don't know what you don't know. So, a few less knuckles and a bit less blood later, and the juddering and stuttering has gone.

As for the running rich, I'm still running the jet at 15 flats from top so I'll keep an eye on that. Might still give the carb a good service, when I've had some time to enjoy Geraldine. (That's the car, not my wife)
Philip

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simmitc
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Re: Running rich but stuttering (and stinks!)

Post by simmitc »

Hopefully you re-torqued the head after a heat cycle? Remember to check again after 500 miles, and recheck the valve clearances at the same time.
PhilipW1039
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Re: Running rich but stuttering (and stinks!)

Post by PhilipW1039 »

I didn't do or know any of that so thank you; duly noted. I might do all that when I drain the system to replace the timing chain cover seal, as I have the stupid heater which has to be taken off before the rocker cover will come off. Might replace that with the tap style at the same time.

Thanks again for the input.
Philip

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simmitc
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Re: Running rich but stuttering (and stinks!)

Post by simmitc »

That sounds like the pattern heater control valve that was around for a good few years. ESM now offer a better quality product. See the description for https://www.morrisminorspares.com/cooli ... es-p829641.
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