The Triumph Dolomite Club - Discussion Forum

My 1850HL has been having troubles with misfiring. Investigating it today between showers, my timing gun shows that although I have sparks on the king lead from the coil, there are no sparks on the leads from the cap to the plugs. The inside of the dissy cap looks like the photo shown. To me it would appear that something is missing from the central post, although I haven't another cap to compare. Am I right?

The other photo shows the rotor arm. It looks a bit burnt to me. What do you think?

Assuming I need replacements, who sells the best ones? These are about 2 years old but have only done about 2000 miles.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

Looks like the carbon is missing or very worn in the dizzy cap
take a look at the second pic here https://www.ebay.co.uk/itm/Triumph-Dolo ... SwYv9eMJca

As above Mike, that might well be your problem Probably has the Corona virus

Tony.

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NOW A CLUB MEMBER 2017057

Thanks. There is no sign of any carbon thing at all, just a hollow circular cup. Can any one recommend a supplier of decent quality replacements?

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

I did some measurements on my spare 1850 set-up.

This is a piccy of my carbon contact. It has a distinctive pip on it.

If you put a pair of callipers across the plastic concentric rings and the carbon brush I measure 3.57mm.
This gives you an idea of what to look for. It is not like the Sprint / MGB dizzy with the carbon brush on a spring.
I also measured the d.c. resistance between the brass contacts in the cap and the moulded carbon pip. It came out as <10 ohms.
As for replacements , the 1850 / TR7 / Vauxhall -Bedford replacement is nowhere near as common as the Lucas dizzy caps, so I would imagine the cheap-and-nasty replacement merchants would not bother with re-making this one.
Ask if it comes in an A.C. Delco sealed box, or go for good 2nd hand.
Please do let us know if this solves your misfire problem of earlier.
Tony.
Edit :- I've just noticed my original one has 3 moulding marks inside near the rotor segments "4" etc; etc; The piccy of yours doesn't show any moulding marks so may be a copy; in spite of my thoughts.

https://www.ebay.co.uk/itm/Triumph-TR7- ... xyQj9RLLB8 This one is from Robsport on ebay Mike. I have had lots of stuff off him and its always been good. I would replace the rotor as well unless the ball on the spring is nice and smooth. https://www.ebay.co.uk/itm/Motorcraft-d ... Swi5VeOeN8 There is also this Motorcraft one which is as near to o/e as you will get, but more expensive.

Tony.

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NOW A CLUB MEMBER 2017057