Morris Minor Owners Club

My traveller has started misfiring under load and is getting worse! starts well, idles well and engine revs very well when stationery. have checked leads, initially assumed it was a fuel problem but don't think it can be. Would appreciate any suggestions from anyone who may have experienced this kind of problem.

thanks very much

Steve

pick and mix
for starters

condenser?
points /gap /pitted
intake manifold leaking
carb sticking
timing slipped/vac advance stuck /leaking?
dizzy cap shorting/spring connecter broken
rotor arm

etc

good luck

Thanks ..have started to work through list.. Manifold bolts a bit loose but didn't sort ! Re.vacuum advance ..am I right in thinking that to check you disconnect from carb and suck and should hear it click? If so mine doesn't and could point to the problem - also rotor arm quite pitted and have cleaned - could this have been caused by sticking vac adv?? cheers. Steve.

Have looked at vac adv again..sucked whilst looking for movement anywhere in the dizzy- no sign of movement. Dizzy is a 25 D .

steve

Vaccuum advance is effected by vacuum from the inlet manifold being placed against a diaphragm in the unit attached to the side of the dizzy. If you lift the dizzy cap away, there should be a coiled wire hooking onto a pin on the dizzy base plate. When vacuum pulls the diaphragm, the coiled wire pulls whole base plate around clockwise by a few degrees, with the effect that the points (or ignition module if you've gone electronic) end up a further further round in the cycle. The cam therefore opens the points a bit earlier in the cycle, thereby 'advancing' the timing. (All this in laymans' terms - as everything's continually variable according to the amount of centrifugal advance going on in the bowels of the dizzy.)



If the base plate isn't moving, but the coiled wire IS hooked around the pin and reasonably taught (some wire loops too big for pin so use the nurled wheel to budge it up into contact), you have either got a split diaphragm or a split vacuum hose. I'd say the hose is more likely to have split if it's a plastic one, so replace that first (it's cheaper!) and if it doesn't make a difference, replace the vac unit. At least you'll have removed any margin for failure by that point.

SimonBBC is an excellent supplier of this kind of stuff. Unlike Distributor doctor, he works with brand new remanufactured (Chinese Lucas) distributors, not refurbed originals. Now, a lot of people have issues with that because Chinese normally means cheap and unreliable, but anything is going to be better than a crusty old 50 year old dizzy! And how many of us are covering the sort of mileage to justify £300 on a reconditioned distributor. I should hope you'd have change of £20 for a new vac unit and hose.

Or alternatively, replace the lot if your dizzy is a bit slack (wobble in the cam spindle, etc, cruddy baseplate, rattling).
http://www.simonbbc.com/distributors/4c ... -rotor-arm

My view on matters like these is to remove, inspect, reduce to component parts, and assess. If it's good, put it back together knowing it's been cleaned, inspected and won't give and trouble. If it's worn, replace the consumable parts to restore optimum performance. If it's knackered, skip and start anew. Do one significant component each weekend (carb, fuel pump, dizzy, water pump, starter, dynamo, control box, etc etc etc), and in a few months there won't be a single part of the overall "engine management system" you're not familiar with.
Nothing quite like that piece of mind on a dark winter's night!!

Good luck!

michael

When did you last fit new spark plugs?? Or a new air filter?? Also worth checking the connections at the coil. As above - if the vacuum advance is not working, it may be time to cut your loses and fit a new dizzy - either Accuspark or Simonbbc (I believe they are both sourced from India rather than China) - up to you if you spend the extra on an 'electronic' one - I would stay with points. The 45D dizzy is a better/improved model - and that's what i would go for. I'm not convinced this is the cause of your mis-firing under load - but at least it renews everything in that area - so it's a good starting point!

thanks very much - cant see any sign of movement and given that whole unit looks very tired I think the easiest thing to do is to replace it . thanks for the link - am going to try them- much cheaper than ESM and others! Cheers Steve.

well, have taken Bmcecosse's advice and gone back to replace spark plugs as first option...they have been in for about 2.5k miles since I rebuilt engine. I may be premature but everything now seems ok.. So The new diz can go on later!!!

If the vac advance is not moving - it does need replacing. But it was never likely to cause misfiring - it just causes 'lackluster' performance and poor fuel economy. What make were the old spark plugs? BMC Works always used Champions - I see no reason to vary from that.......

I've heard mixed reviews about modern Champion plugs. N6Y/N7Y etc were the recommended for Rover 2000's, and I think I'm remembering correctly when I say N9Y (??) was used in the majority of standard compression ratio A-series engines during this period. It may simply have been a bad batch, but there were a fair few 'duffs' reported a few years back - at least in our circles. They are also produced somewhere in Near/Middle/Far East area.

The majority of us in P6 circles are running on the equivalent NGK plugs these days, and we have one member doing 14,000 miles a year without issues.

The equivalent NGK to the N9Y Minor plug would be BP7ES. Please correct me if I've got that wrong, but I'm almost 100%.

As BMCE says, there's no real reason to vary from the original spec. You shouldn't mess with the heat ranges unless you have seriously adverse running issues (i.e. white/sooted plugs) - but even then better to address cause rather than symptom - and iridium tips, etc, are a wasted effort unless you're running about 11:1 compression and revving to 7000 rpm. Still, it may be useful information if anybody has reported any duff Champions recently?

Michael

Some months ago I ran a thread on my Traveller misfiring under load. I went through the whole gambit of usual causes, even stripped the head completely, oil tested the bores, fitted new everything. I spen weeks on the thing and spent a fortune. The final answer took 30 seconds to fit and cost £4.50 - the air filter.

As for spark plugs, like BMC, I have always fitted Champion, and can recount several examples of engines fitted with non-Champion plugs where there have been problems. Reverting to Champion has solved the issues. However, each to their own.

I have never had the slightest problem with Champions - I have had terrible problems with a (new) set of NGKs on a mates MGB....threw them into the field behind his house - and fitted an old set of Champs from my tool bag - all the problems were gone........ QED

n9ys for me

N5s for me

Ngks , they use em on Japanese bikes , very reliable