Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Misfire on 1966 +4 with TR4 Engine

I have a 1966 +4 with a TR4A engine rebuilt circa 5 years ago. Two issues have become apparent in the last 3 weeks :-
- took it on the road 3 weeks ago, started fine but under drive was periodically misfiring....seemed to cut out then go again.

- started it today ok, then suddenly misfiring and back firing before cutting out.

Have done plugs, plug leads, distributor with new points and condenser and fuel is fine.

Could this be a faulty coil ?

Many thanks,
Dwin

I think there is a good chance it is breaking down with temperature so certainly worth swapping out.
Good luck.

Probably the coil

Especially given its location bolted to the engine block and therefore subject to excessive heat and vibration.

A tip that MOG615 passed to me was to mount it on the inner wing like the crossflow 4/4's

Arwyn

I fitted a brand new (not old stock) Kerr Nelson condenser to our 4/4, same intermittent misfire, total failure after 2 weeks.
I cut the condenser open to see the reason for failure, a spike of solder had been making poor contact & then finally created a hole in foil = poor manufacture.
Replaced the condenser with Japanese one, problem sorted.
.

I think we need a bit more information before being able to diagnose the problem

1 Was it running OK previously , when was that ? Has it stood for a period?

2 Is everything else exactly the same from when it was running before, and no changes made?

3 What carbs are you running , a TR4A was supplied with Strombergs ?

4 Is the distributor tight in its housing , no possibility of it having rotated possibly?

5 Do you have the manifold to distributor rubber piping in place to advance/retard the ignition fitted ? Is this in good condition and no air leaks.

6 Check the coil (as per Arwyn above ) it can be damaged by constant engine vibration. (just replace it with a known good one)

7 Check all the electrical connections , especially those to the coil, for wear on the insulation, check the end connectors (usually spades) for continuity

8 With a TR +4 the wiring is so old now that it might have been bodged by previous owners, check for any no-standard add-ins etc. Make sure that there is no shorting to ground/earth anywhere.

Good luck

Thank you all for your contributions and will certainly follow up on them.

Car was running perfectly. It has been started but not driven to any extent over last say 18 months. The car was totally rebuilt including the engine (all new electricals, leads, wiring....you name it, everything new !!) circa 5 years ago. Started having misfire about 12 months ago, replaced condenser and then ran ok. Running on SU carbs. Have done all the usual checks apart from coil and rotor arm.

Cheers.
Dwin.

Hmm, had an issue with a rotor arm once. Turned out to be a microscopic crack which opened up when hot causing all sorts of misfires

Would advise changing the rotor arm to one of the 'red' ones

Arwyn

All the above makes sense.

One point to note is that some new parts are of poor quality these days. Coils and rotor arms spring to mind as well as the condenser reference above.

I once had a pig of an occasional misfire which turned out to be a hairline carbon tracking on the inside of the distributor cap on my Singer Chamois, I don't think I'd have noticed it on my present car ..

OK some other 'points' to consider
Is it definately an ignition issue...use a timing strobe?

Could it be weak fuel mix ie carb jets etc is blocked with crud especially if it has been sitting a long time, try easy start spray does it run better?

An interesting issue Im looking at is distributor phasing ie does the spark happen when distributor cap post is centrally located with the rotor arm? check where arching happens on the rotor arm ....it should be spread across the edge of rotor arm not on the training/leading edge.....