A Lotus moment.....

[Bigbaldybloke]

What checks have you done on the fuel system, what fuel pump do you have, the original mechanical one, an after market one or an electric one. Is it giving a good flow or is it starving the engine at higher revs but has sufficient flow for tickover? A sticky or faulty valve in the mechanical pump may give intermittent fuel flow. If you replace the HT electrics as you mention and still have a problem, the fuel supply is the next suspect.

[2tmike]

Just to complete this post....the issue was the lumenition mounting plate. Initially the dizzy seemed OK but when I removed the carbs to have a close look I found that the adapter plate for the ignition module had somehow become loose. Really strange because the mounting screw is flush with the top of this plate and the module covers the screw so it shouldn't really be possible....probably a suspect thread ....anyway, refitted with new screw and loctite and it runs cleanly through the rev range....or at least it did until the throttle return spring snapped ...oh well, it is a lotus....
Thanks to everyone for all the helpful suggestions

[TBG]

Where in Devon are you? I have just towed in my chums bright yellow one from Devon into Somerset. Burnt out loom in the engine bay. Very lucky there was no fire........................

[2tmike]

Very lucky indeed - I'm in Barnstaple

[TBG]

He was coming from near Abbotsham to me in Somerset. Made it on the end of a rope!!

[TBG]

Update. Wire rubbed through on the heater valve as not properly clipped in. Result dashboard out replacing lots of wires................

[2tmike]

Well, since securing the ignition module in the dizzy, the car has run faultlessly for several hundreds of miles....until today.....driving at reasonable speed on a main road in traffic and the engine suddenly cut. I pulled off the road and after a little cranking it restarted and again ran correctly. All electrics appeared to be working before and after the cut out, but I didn't notice the rev counter that time. I drove on to the next town to turn around and go home and trickling down the main street it cut again and this time it restarted just for a few moments and died. This happened a number of times until I got it into a car park. I did notice this time that when cranking to restart, the rev counter was swinging wildly from zero to full scale but as soon as the engine fired it settled to a normal reading. Anyway, after head scratching and checking wires it restarted and ran perfectly so I drove it the 10 miles home. I've been over all the accessible wiring and thoroughly checked the dizzy module for security an everything seems in order. Does the rev counter behavior give any clue to the problem?

[TBG]

Coil? It was a hot day and coils can play up if they are too hot. That is why mine is in the cockpit above my feet to keep it cool. Problems in the past led to this move.

[2tmike]

Possibly coil related.....the coil itself seems ok with 6k ohms on the secondary and 3.5 ohms on the primary, however....when checking this, the earth from the coil parted company from the spade connector. It may or may not be the cause of the problem but looking at the connector, it was never crimped properly so there's a fair chance that this is at least a contributor to present and past issues. When I rewired the car I replaced all the looms with new from the usual sellers and during installation 5 or 6 connectors (mostly bullets) pulled off when I was making and remaking connections. Why oh why can't suppliers manufacture stuff properly these days !!!!

[Bigbaldybloke]

Must admit I spent about £50 or so on a professional bullet crimping tool, definitely worth it if you are doing much wiring.
Hopefully you have found the cause of your problems!

[2tmike]

So do I, its most disconcerting loosing the engine on a busy road at speed......makes HGVs larger than life....(

[Bigbaldybloke]

I know the feeling, many years ago in a Hillman Imp on a dual carriageway, halfway past a large artic lorry and throttle cable snapped. Not a good experience!

[rgh0]

I know the feeling, many years ago in a Hillman Imp on a dual carriageway, halfway past a large artic lorry and throttle cable snapped. Not a good experience!

At least you had a throttle cable to snap rather than the pneumatic throttle linkage the early Imps had that would slowly die without pumping the throttle pedal if you had any leaks

cheers
Rohan

[Foxie]

So do I, its most disconcerting loosing the engine on a busy road at speed......makes HGVs larger than life....(

Especially when it's a caused by a dead battery, having overlooked reconnecting the alternator after an engine out job, on a 200 mile trip, in the outside lane of a busy motorway on a Friday evening. Of course the indicators, hazards, and brake lights were all dead too.

An important lesson learnt.

[Bigbaldybloke]

Rohan, first two things I did when I bought the Imp was spend £40.00 for a new short engine and while replacing the engine I also replaced the carb and linkage with a Weber and a cable! I guess I didn’t fit the cable correctly otherwise it wouldn’t have broken
I doubt £40 would even buy you a throttle cable now!