Morris Minor Owners Club

Well I thought that we had sorted the problem with Sky's rough running, but we hadn't.

I haven't used Sky for a while, because of various reasons, and we took her for a run on Sunday and all went well except for a little backfire. Took her to work today (12 miles) and it started off ok but after a run at around 50mph she started to run rough again. We continued to Stafford and when I backed off the throttle, going down hill, she started backfiring quite severely. (it did get the tailgater behind to droo back at least

At lunch time I cleaned out the fuel pump just to be sure and turned dissy back a little, just to be sure I hadn't advanced the ignition too far.
THe trip home was pretty much the same as the trip into work but she is running a lot rougher, even on tickover.

I've done all the routine checks again, no air leaks as far as I can see, plunger falling freely and oil in the dash pot.

I know I've asked this before, but any help would be really appreciated.

Brian

Hi Brian, Im around tomorrow if you need a hand. It sounds like timing/points/condenser probs or the mixture is way out.

Lee

Thanks Lee, I'll call round tomorrow.

Check valve gaps as a starter - and do a compression check if you have the gauge !

Will do that bmc, a compression test sounds a good idea.

A big thank you Lee for all of your help tonight.

Just as an update, we, well Lee really, checked and adjusted the valve clearances, closing them up a bit and checked the compression with all cylinders well above the 100 mark.

Checked the point gap which was a bit small, but as big as we could get them, so we put the old points back in and adjusted the gap.

Still ran rough, so Lee adjusted the timing and richened the mixture by two flats. This has evened the running a lot, so I'll take her to work again tomorrow and see how it goes.

Thanks again

Compressions should be > 150 psi!

Glad to help. It was a pity my compression tester decided today was the day to play up though! They were all around 130psi, I have known A series engines run with much lower figures than that. The main problem was the points gap being too small, the contact set wasnt a very good fit on the baseplate so we cleaned up the old points and put them back. The valve clearances were wide and were reset. The car already has new plugs, leads. condenser and cap. It would be worth getting a decent set of new points. Let me know if you need any more help, that timing chain is noisy and could do with changing.

A nice little Minor! Hope it goes ok tomorrow, let me know how you get on.

Lee

As long as all comps were similar - then just reflects general engine condition. But for good running - should be better than 150 psi.

Yes they were all similar, it would be nice to have 150+ but it is presumably an engine with a few miles on it, it was quite smooth really.

Well she ran well into Stafford today, you can still hear that sh'e not running completely even, but so much better than she had been. Thanks again.

I will look at rplacing the timing chain fairly soon to see if that evens out the running

Brian

It won't be anything to do with timing chain! Don't waste time/effort/money on that!

bmcecosse wrote:It won't be anything to do with timing chain! Don't waste time/effort/money on that!

Appreciate the comment BMC and anything that saves cost and my back is appreciated. (I havent worked on Molly for the last couple of months due to a painfull back)

One thought was that if the timming chain was slack, it would effect timing and give poor running, but I bow to your greater knowledge. I'm really appreciating all of the comments, as it's the only way I'm going to learn.

I'm ok with the straight mechanics of part replacement but not the skills of engine tuning, carbureter / ignition etc.

As I said, she ran much better this morning,, but not as sweet as she has in the past and not with the same acceleration as she has had. She will tickover again now which she didn't enjoy on Monday evening, but on tickover you can still hear her dropping revs regularly which is also felt while I'm driving.............but at least she is driving again, thanks to Lee.

Check the vacuum advance mech is working. Also general ignition system refurb does no harm.

Vacum advance seems to work fine. Movement when you suck on the pipe, vacuum at the carb end, plate springs back when you stop sucking.

Sorry, what do you mean by ignition system refurb? She's had new plugs, leads, dissy cap, rotor, refurbished the points and tried different coils.

Hmm - well - doesn't leave much - does it! You don't mention condenser - or the little 'low volts' wire inside the dizzy........
Otherwise - you need to turn your attention to the carb!

Yep, condenser and low volt wire changed as well. (The low volt wire was off another dissy, but I tested the resistance while wiggling it and it was <0.01ohm so assumed ok)

On the carb front, checked the bowl was clean, slider works cleanly and oil in the dash pot. When lee richened the mixture by two flats it did improve things although the plugs looked a good colour.

When do the backfires happen, on or off the accelerator?
It might be worth blowing some carb cleaner down the main jet and see what emerges into the float bowl.

Nice to see you bowling along the bypass today! That colour does stand out. Sorry its still not as good as it should be, will have to look at it again, Im thinking the timing is still out.

Check coil is wired right way round. Have you tried a nw set of Champion plugs ? N9Y should be fine.