Ignition woes from series one 4.2

Hello cat lovers, I purchase a roadster that had been sitting for over 40+ years. I went through the car to make it road worthy by replacing the brakes fuel tank, water pump, radiator clutch master and slave cylinders front and rear brakes steering shaft bushing ball joints tie rod ends and a host of other things.

After getting the car running well, I decided to do a full tune up with new wires, plugs, rotor points and condenser but I’m now having a misfiring challenge. I’ve tried replacing the dizzy and coil but the misfire still persists. the firing order is correct and I’ve also drained the fuel tank and i’m beyond frustration, I’ve tried different wires and caps but failed effort, I hate to have it towed to have it fixed, just to know it is something simple, what am I missing, help!

something very simple, HELP!

One suggestion would be to put the old parts back on, I’d start with the old condenser and points/rotor, then the cap. If everything is connected correctly, defective parts are certainly a possibility.

I remember low quality condensers being a problem 20 years ago, let alone now when points type ignitions are less common than back then.


Tell us under what circumstance it misfires
There can be many reasons causing it

69 OTS


Have you or a PO replaced the ignition high tension leads (aka spark plug wires)???

And the caps?

There are a lot of faulty new repro spark plug caps.

I would measure the resistance from cap to each plug and possibly each cap separately.

A friend of mine had a new loom / set of spark plug wires with conduit and caps on his car after a professional restoration.

Had a lot of misfiring. The workshop was sure it was fuel related. They replaced fuel pump, hoses, fuel filter and fiddled with the carbs. No help.

In the end it turned out to be the spark plug caps. They are / were supposed to have 5k Ohm resistance. Three did, one was 20k Ohms and two were infinite on my multimeter. :-o

Also the connections on the dizzy cap may be iffy. On my ex S1 2+2 I once saw a difference for nr 2 and 5, I didn’t have the rubber boots on the ends so I had had some water seepage into the connectors which resulted in corrosion. I found this by measuring the cables and got 20-24 Ohms on all other wires but IIRC nr. 5 was like 400 Ohms and nr. 2 was 200+ Ohms.

Opened and cleaned the connectors in the dizzy end and all was good, no misfiring and a steady idle. :slight_smile:


I was given a Mk2 that had a persistent misfire despite having had new leads, plugs, condensor, cap, coil, points, rotor etc; in other words everything ignition related. Owner had spent 2K trying to get it fixed ( by Jag agent, no less). The problem was fixed in 30 minutes; the bush in the distributor was worn and allowed the points gap to vary as the engine ran. Remove dist cap and rotor and check distributor shaft for sideways movement. Good luck.

Hello bdragon, I did put the old ignition pieces back but the results were the same leaving me very puzzled. The results caused me to change the dizzy and had me scrambling to find ways and means to resolve this issue

Hello Pekka
I’ve done all you mentioned and what I’ve found puzzling is the number 2 and number 5 plug has the power concentrated to those two plugs, the spark is very strong and enough to kill the power to the distributor while the others would be very week causing the misfire and backfiring through the resonators

Would you explain this more?

Spark number # 2 from the fire wall and # 5 has very strong sparks while the others have very low intermittent spark, I spoke to Dave Walsh and he said it could be the distributor plate. I remembered simply removing the dizzy from the block and replacing the condenser points and rotor with no interference with other component. When I removed the plug wires while the car was on, the car would literally die if the plug wires were not returned to the plugs. There was not enough power going through the other plugs for a good spark, their sparks are quite weak…

I’ve seen this symptom due to a problematic cap. Sometimes they can have a crack that is invisible.

It’s not what you look at that matters. It’s what you see.
Henry David Thoreau

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It doesn’t seem like an accident that 2 and 5 are 180 apart. Is the cap seating properly?

You say the cap is new, the one on the photo, especially the second does not?

Also, have you ever checked compression?

Hi Michael, the cap is in good working condition; however I did try other caps and the results are the same. The Triumph TR6 shares the same caps rotors points and condensers and I tried a few. I’m not sure what to do next

The compression shows 150 lbs across the range. The car ran perfectly before I decided to do a full tune-up

In your photo with the yellow wires… what the heck is going on here?


The shovel connector broke while going back and forth with the distributors with what’s causing the misfire; however the problem remains the same. Once the issue is resolved a new connector will be installed…

Are your plug wires fitted into the plastic tube to the head and then the cardboard conduit running along the plugs?

Some say a 6-cylinder will not crossfire but I think they can and there is an easy test you can do with a timing light.

Do you have a dwell meter to see if dwell angle is relatively stable at idle ? Installed a vacuum gauge to check that? Is your ignition timing about 10 degrees BTDC at idle?

Hi Kris, I’m not familiar with that test, can you explain or do you have a video that illustrates the procedure?