Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 76 Plus 8 Misfire

I have an intermittent fault on starting my 1976 +8 after not being run for some time - it misfires and seems to smoke, which I assume is unburnt fuel and a bit of oil on the cylinders not firing correctly?? I have changed plugs and cleaned distributor cap posts (which were a bit corroded) rotor arm end and it appeared to fix it. However today, 2 weeks later, problem is back. Appears to be 2 cylinders on right bank of engine (having taken 4 plugs out and 2 are wet), making me believe it cant be fuel as other 2 cylinders that side would presumable not fire correctly either. I am thinking to change distributor cap and rotor are as next step - what is the right one??

All help appreciated, Thanks

You sound to be well on the way to finding it John, it is possible the leads are breaking down if they are older ones. Changing the cap, rotor and leads is fairly cheap really I'd tend to go for them and then see where you are..

Guys

My friend John Merton , a lurker here, sent me the following tips from a very similar problem that he experienced.

Quote
I had a similar problem which took me years to sort out.

Basically, with two spark plugs not firing on one side he should check whether or not the alternatives on the other bank are not firing as well. This is because, if it's a carburettor model like mine, each carb feeds two on one side and the alternative two on the other and there is no mixture balancing between them. He should pull a lead from one of the dud cylinders and check with engine idling whether there is any spark. If there isn't the source of the problem is obvious, if there is, it's a carburettor problem irrespective of how damp the plugs look.

Unquote

I hope that helps you

There was also a workshop note for the MGV8 that two plug leads on one bank shouldn't be next to each other. I dont recall which two but a google search should produce the info.

Here: NB .. "make sure plug leads 5 and 7 don’t run next to each other (5 and 7 are adjacent in the
firing order and cross firing can occur)"

And.....NB: the cap and/or rotor arm are often responsible for various chronic running problems - always check
these first before anything else!

Had similar problems a few years back (1980 +8). The post on the rotor arm was cracked, problems low revs not at higher one, 2000+. The replacement also failed! One of the little rivets holding the top of the arm in place fell out, so the arm when spinning was lifting and not hitting all the cylinder posts.

I had problems with the distributor on my 85+8inj. I bought a replacement from a reputable company and it was rubbish, it spurred me on to convert the car to a distributor less system and it has been perfect, no misfire or rough running and better control over ignition timing
.
David Byrne

That is a very good tip/warning .

Thanks to all for the comments and recommendations. I didn't know each carb worked both cylinder banks, interesting. Apparently before I bought the car it did have muck in one carb which required cleaning. I am wondering now if it is a combination of electrics and carbs!! Much to do!