Lotus Elan

Hot (not) starting

PostPost by: Steve G » Thu May 10, 2012 3:15 pm

When I was in traffic for the Goodwood Breakfast Club on Sunday, the queue wasn't moving, so I turned the engine off. The bugger wouldn't restart. (Incidentally while I was stranded I had a thumbs up from an Elan M100 owner, an offer of a car swap from an Elise owner and a glance over the shoulder from an Elan Sprint owner!) Coolant temp gauge read 90 degrees. Once the coolant temp had gone down to around 70 degrees it started again. Before that it sounded like it was turning over with no spark at all. Once started it drove home without skipping a beat.

What possible causes are there for the engine not starting when hot? I'm taking the car away for my birthday tomorrow, it will be the first proper trip with my wife since I bought the car two years ago. My wife has booked a hotel in the country somewhere and I would like to avert disaster (or at best an annoying pause in proceedings) by at least knowing the possible cause.

Car passed its MOT yesterday, headlights not working was just a blown fuse, handbrake was adjusted and passed with no advisories.
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PostPost by: prezoom » Thu May 10, 2012 4:47 pm

You might have experienced "heat soak" in the carbs, where the fuel expands and overflows into the intake manifold. Buy the time your engine cooled down, the excess fuel had evaporated and it would start as normal.

I know if I even bump the accelerator pedal when my car is hot, it will produce just enough extra fuel to make it hard to start. It then becomes a foot on the floor situation, and cranking the engine enough to clear the excess fuel from what I dumped from the accelerator pump and what was in the cylinders.

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PostPost by: ardee_selby » Thu May 10, 2012 4:52 pm

Steve,

As Rob has said...

Sounds like a classic heat soak scenario affecting fuel. (But first...are you still using Lumenition Optronic + rev limiter? i.e. you haven't reverted to points and a good ol' condenser, or anything, that may be heat affected)

When you switched off, assume electric fans were also stopped. i.e. they haven't been wired to allow for running-on to reduce heat soak effects.

Also, this quote, from a Sprint owners handbook, has been posted before:

"Starting the engine when hot: If difficulty is experienced in starting a hot engine, the accelerator pedal should be fully depressed and the starter operated. Release the accelerator immediately the engine starts"

Is that the technique you used?

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PostPost by: Steve G » Thu May 10, 2012 5:09 pm

Aah, so not three prods of the throttle before starting and then not touching the accelerator then? That's the advice I received for starting the car cold (and it works very well).

That is great advice thanks, I will try that tomorrow and report back. I've got a lot to learn about carbs, my first car and every car since has been fuel injected. :roll:

I'm still on optronic lumenition and the rev limiter that I fitted (tested to work just the other day). I have an electric fuel pump but not electric fans, it has original crank driven fan and radiator.

Does optical ignition not suffer when hot like condensor and points then?
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PostPost by: ardee_selby » Thu May 10, 2012 5:16 pm

Steve G wrote:Does optical ignition suffer when hot then?


I have Lumenition Optronic.

No adverse temperature effects in my experience. I just wanted to check you hadn't reverted to conventional system to eliminate a possible condenser problem.

Cheers - Richard
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PostPost by: alexblack13 » Thu May 10, 2012 6:29 pm

Sounds, as the guys say, to be almost certainly flooded. The 'cooling down' probably allowing evap of the petrol in the manifold. If you then gave it a few pumps and tried to start it, It most likely wouldn't..

As the book says, Throttle foot to the floor and crank it till it fires,. Then foot off smartish...

You will get the hang of it. :wink:

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PostPost by: Steve G » Thu May 10, 2012 7:42 pm

Thanks guys. Every day's a school day.

By the way, I edited my post as I misread yours but you'd already quoted me. I think I get it though, optronic good, condensor bad (in terms of heat failure).
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PostPost by: Steve G » Mon May 28, 2012 11:05 am

Had the problem again on Sunday, the engine got hot in traffic (95 on the temp gauge) and then conked out and wouldn't restart in a really bad place blocking the road but only 100 yards from my house. I tried the open throttle technique but it wouldn't catch. I walked back to it after half an hour and it started first time.

I've really got to get to the bottom of this as it's killing my confidence in taking the car out. Is there a way I can tell if it is due to engine flooding or not?
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PostPost by: nebogipfel » Mon May 28, 2012 11:29 am

Both condensers and ignition coils can break down when hot.

The fact that the car "conked out" sounds more like an ignition failure problem rather that fuelling IMO.

It's not unusual for a twinc to get a bit grumpy (fluffing and spluttering a bit) in traffic queues on a hot day but I have never had one quit on me.
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PostPost by: Steve G » Mon May 28, 2012 11:43 am

I misled you there, it didn't so much conk out as I 'allowed it to stall' shall we say. :oops:

I've got Lumenition Optronic ignition. It was a bit spluttery and hesitant when I finally got moving after the traffic.
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PostPost by: Galwaylotus » Mon May 28, 2012 8:59 pm

Electric or mechanical fuel pump? Vapour lock? :?
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PostPost by: ricarbo » Mon May 28, 2012 9:28 pm

You could check for a vapour lock by taking the top off one of the carbs when the symptom appears. If there is no fuel in the float chamber, you have a vapour lock problem.
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PostPost by: Steve G » Tue May 29, 2012 8:17 am

I have an electric fuel pump. When the coolant temp drops to around 70 degrees Celsius on the gauge, it starts.
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PostPost by: bast0n » Tue May 29, 2012 8:27 am

Steve G

In days of old when chaps were bold and coils got hot and spented..................eh, what?

Before I moved my coil to above my feet to keep it cool I had three failures of the sort you mention. Once on a German autobarn in the high 30s and again in Lugano in very hot traffic - very embarrassing -changed coil and all ok until the next time..............never had a problem since the coil reposition.

I was given this advice by a well known racer of Elans who puts his where the heater was before he whipped it out to save weight. Mine is just above my right foot,RHD, and is neatly out of the way.
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PostPost by: Steve G » Tue May 29, 2012 8:48 am

That is very interesting as my coil is mounted on the right hand (offside) radiator mount. I did this following advice to get it out from under the carb intakes. As I don't have the airbox in place (but I do have pipercross socks instead) there was a danger of fuel leaking onto the ignition coil. This does mean that the ignition coil is very close to the radiator, about 1 inch away. I have the original StanPart radiator.

When you say 'above your feet', do you mean inside the pedal box, on the cabin side of the bulkhead?
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