Morris Minor Owners Club

Hi,my first time on here,just joined the club.
I have a miss fire problem with a 1098 engine,some times it runs ok then all of a suden misses,not back fire just seems like fuel starvation.
At the monent I am seeing a lot of air bubbles coming through the fule line from the su pump to the carb,but this may not be correct I cant see it been my problem.
So far I have changed the dissy,fitted electronic points,after trying orriginal points first,new HT leads.plugs,checked the carb over,float chamber,had the head off and reground all the valves,by past the ignition switch but still no joy.

Has any one had this problem ?

Steve

Hi Steve,
Here's some questions.
When you say misfires, does it break down on any specific cylinder, or does the engine stop on all cylinders momentarily?
Is the engine at running temperature when this happens?
Some things to try.
Do a compression test. Could be a sticking or leaking valve. Check valve clearances. Check the operation / flow of fuel through the needle valve / float etc. And that the carb jets are clear of obstruction.
I'm assuming that what you've done to the ignition system with regards leads, connections, trigger system etc. is all good.
Hope this helps.
Jawelnofine.

Steve
" all of a sudden " usually means something electrical.
Given what you have replaced already what state is the low tension lead...coil to distributor...like ? Connections sound and clean and wire good..no chaffing, nicks damage,etc.
Another thought, you've checked the carb is the fuel pump filter clean rather than clogged up ? Don't forget to replace the washer with a new one to stop any future leaks.
Bob

Thanks for the replys so far.
It feels like it cuts out for just a second then back in again,it can run for 15 mins ok then starts to miss and then just sudenly run ok,its getting worse now ive been trying to fix this for about three weeks now.
I forgot to say I have changed the coil for one new one and two other used ones.
Ive not done a compression test since I reground the valves but befor it was only about 130psi on all cylinders.
Yes checked the fuel pump filter nothing to see.

My next thing to try was to fit my strobe light.powering it from an inverter.That way I could see if the ignition is failing by looking at the strobe light,ie regular flash when running ok and irregular when I get the problem.

Steve

Hi Steve,
I'd agree with Mogbob. It has to be a dodgy connection.
Try eliminating a large part of the harness by powering the coil straight from your battery. See how it runs then.

are you running standard coil thease sporty ones are not the best , cheak connections to coil are good

I have run the low tension wires direct from the battery,and made up an extra earth lead to the engine,I've even thought could it be a can follower sticking in the up position but I've not followed up on than one yet.
This is driving me so mad I bought another engine the other day as a back up plan,but I'm not beat yet.

Steve

I forgot to say I've tried three coils all ready one was brand new and the engine missed straight away,I have now got another old one on the engine I just bought bought.
Maybe I'll give that a try!
Steve

It's NEVER the coil - as you have adequately proved by trying 3 with no improvement!

bmcecosse wrote:It's NEVER the coil - as you have adequately proved by trying 3 with no improvement!

Now were have I heard that before.
Steve

Tried the old coil and set my strobe light up so I could see it as I drove the car,unfortunately after a couple of miles the strobe light burnt out so I didn't get to see if the problem was ignition or not.but the principal was a good one !
True to form after another mile it started to miss fire.

It's MUCH more likely to be the condenser. Can you beg/borrow/steal a complete spare dizzy to try?

Ive already fitted a new dizzy with points at first still no better now with electronic points so no condenser is fitted.

But thanks anyway.

Keep the ideas coming.

Hmmmm - and 3 different coils with no improvement ?? Was a different dizzy cap and HT leads used ? And different rotor arm ? Is the carb ok - piston rising and falling easily? It must then be a fuel supply problem - so I would do the fuel flow test I described earlier in the thread above ^^^.

I'm still struggling with this intermitant miss fire,I have now got extra earth cable direct from battery to the engine and have just replaced the ignition switch for a new one and still it missfirers.
This all started after the electronic points fitted by the previous owner failed,or at least that's what a thought at the time as the engine would not start and I didn't get 12v at the coil in any position of the dizzy.
I replaced the electronic points for normal points at first and then the engine ran but with a intermittent misfire, I then tried new distributer cap and leads,then several coils.
Fitted new spark plugs.
Checked carb,piston drops as it should,seat is approx one and a quarter to one and a half turns out,new air filter fitted.
Fuel pump checked seems OK apart from air bubbles do come through to the float chamber but as this has a vent hole I don't think it should be a broblem.
I then took the head off,gasket looked OK,re ground the valves and re fitted with a new gasket.
Brand. New dizzy fitted at first with points then I bit the bullet and bought a twin pack of electronic points and fitted one of them.
At the weekend I fitted extra earth to the engine and replaced the ignition switch cleaned up all conections at the fuse holder but still I have the problem.
The wife is fast loosing patients, anyone got any better ideas.
Steve.

Try a direct feed from the battery to the coil, and also a direct wire from coil to dizzy. There must be a dodgy connection which is 'making and breaking' -you've changed everything else!

I've got direct wire from battery to coil and the negative side of the coil goes direct to the electronic points.
Any way been out in the car this evening and true to form it missed for half the journey going,approx ten miles but never missed a beat coming back in the dark.
It was quite cool tonight so I wonder could it be something like the thermostat not opening all the way,I have been thinking that the engine feels a lot hotter than I remember my two previous moggy engines running but have assumed its because of the unleaded petrol.
What do you think,anyone !
Steve

Well - could be sticking valves I suppose - Richard had that. Are the valve gaps all correct - no broken springs? Although if it was a sticking inlet there would be a 'blow back' through the carb - and if a sticking exhaust probably get a 'backfire' in the exhaust. Certainly looks like you have eliminated any Ignition possibilities - and fuel would affect the whole engine - dying and then picking up again, that sort of thing, rather than just a 'miss'. Perhaps try larger valve gaps (say 25 thou) all round to see if that makes a difference? And possibly try a lower value thermostat - say 74 C. I can't remember if you have changed spark plugs - hopefully not NGK..... Perhaps try a set of Champion N9Y plugs at 25 thou gap. There is NO advantage in the stories we sometimes hear about 'larger' gaps with electronic ignition... Try to do just one trial/change at a time - to pin-point the trouble for future reference.

Just fitted a new 82 degree stat as its what I had,weather permitting I will try it tomorrow.
You say you hope I have changed the plugs,well I have but I fitted champion N5C not the N9Y you suggest, what's the deference ?

Steve I recently had a very similar problem on my 1098 went to Bristol last week a 200 mile journey for me and 14 miles into journey a misfire occurred it happened a further two times anyway prior to this like you I changed everything electrical yes even the coil! I hear you say i"it's never the coil". And to be fair to our old friend it wasn't the coil.

So on this occasion I opened up the point gap and it cleared and then it came back another 70 mile into journey. I fiddled with the LT Lead in distributor and in desperation changed the rotor arm cap even though I had already changed it prior to the journey. Another 15 -20 mile into journey did it again anyway got to bristol with it. The fault was totally intermittent.

When I got to Bristol I got the carburettor blown out (which was pretty clean) the points and timing reset and had the exhaust re-sealed at the manifold then drove 200 mile back and it never missed a beat. Been out in it today and touch wood it has not surfaced - fingers crossed. Without doubt these faults can be very frustrating. I am sure you will sort this and I will be interested to know what you did to cure it.