Rough running and refusal to start.....

[theelanman]

Ok so today was probably the hottest day of the year I took the Lotus out for a run all ran fine for about 40 minutes then it started stuttering as if it was missing on a cylinder but a quick rev of the engine cleared it with a bit of a pop and a bang and a puff of smoke and then returned to normal for the next five minutes after that it happened again and again and again so it began missing every five minutes until I rev the engine to clear it
I parked up and then could not get the car started
I finally bump start the car and it would only run cleanly above three and a half thousand RPM under that it was as if it was missing....no power at all....I had all the plugs out and cleaned them
I am slightly confused as I finally got the car home having revved very hard and now the whole garage just stinks of petrol
I am wondering if I have a blockage in the fuel lines or if my carburettors have decided to detune themselves in this hot weather
previously to this the car has run faultlessly including trips to Le Mans etc just wondering what people think
thanks
Gareth

[mbell]

What carbs?

The less that 3000rpm on webbers might point to idle circuit issue or could be fuel level or electrical issue.

[Robbie693]

Mine was pretty ropey today too, not as bad as yours by the sound of it but plenty of clutch slipping needed to get away.

Anyway - I've had similar problems to your own with electronic ignition modules going bad (if you have one) and coils too, particularly in the heat. if you're using points still then perhaps a dodgy condensor?

Robbie

[theelanman]

Sorry.......yes I have webers and luminition

[richardcox_lotus]

My first thought would be overheating coil. If it started banging I'm thinking spark into the dizzy at the wrong time.

Can't comment on luminition but presumably same effect if going wrong

Good luck
Regards
Richard

[theelanman]

I put a new coil in it a few months ago as it would refuse or be very difficult to start when hot.....
this solved that problem and it hasnt been problematic since........

Im thinking Luminition........I have heard many people have problems with these when they get 'old'........
Ive had this 5 years and it came with it on....so who know how long it has been on for........

I think I'll change it out.........

what do people think is the best replacement.........

[theelanman]

one point I forgot is that I was always able to start it from a bump start..........couldn't do it from the key.....
hence my tendency to point the finger at Luminition

[Robbie693]

I'm using the Powerspark unit at the moment:
http://www.simonbbc.com/electronic-ignition-kits?zenid=e1b375d5312182e55f1fdf6bf5206ab8&sort=20a&filter_id=15

I did have one go bad but they replaced it for me and suggested I used a solid state coil too, which I did, and the current one seems ok at the moment. I figured that they are cheap to buy by comparison to the Aldon/Petronix units and I could just fit another if this one packs in... I don't blame the module entirely for breaking down - I had a lot of heat issues too which I think may have contributed to it's early demise. This may be the reason I could never get it to run well on points either. They're a nice bunch to deal with, located close to Paul Matty in Bromsgrove.

[DavidLB]

Could it be fuel vaporisation perhaps modern fuels do this quite readily, my prewar car did it yesterday for the first time in 50 odd years ownership

[Quart Meg Miles]

Could it be fuel vaporisation perhaps modern fuels do this quite readily, my prewar car did it yesterday for the first time in 50 odd years ownership

Indeed it could be, the alcohol in modern fuels killed my car in hot weather until I fitted an electric pump in the boot. Never a problem since.

Gareth, check if the fuel pump has petrol in it when it is misfiring badly. I don't understand why you could bump start it though it might have cooled by then.

Personally I would take the opportunity to refit the contact breaker; add simplicity!

[rgh0]

Ethanol has a lower vapor pressure than many components in fuel which is one of the reasons why carb cars struggle more with ethanol than fuel injected cars where vaporisation is less of an issue due to the high pressure spray. Ethanol itself is not the issue as the fuel formulation is done to achieve a specific vapor pressure that is typically higher in winter than summer

Problems with fuel vapor locking is often a winter to summer transition issue where winter formula fuel which vaporizes more easily is used in a car in hot weather

cheers
Rohan

[Orsom Weels]

I think I would err to electrical gremlins, I had both my Elan & +2 out Sunday & yesterday in 30 degree plus temps, both with cheap Murco 95 ron fuel with no additives. Both were quite happy, never missed a beat & would re-start hot or cold with no problems. Unless you were unlucky enough to find a duff batch of petrol ?
I too am using the Power spark from Simonbbc, both over 5 years old now & still performing perfectly. For the money, I think they take some beating.

Regards, Tim