Lotus Elan

Running Problem

PostPost by: wobblyweb » Wed May 11, 2005 9:56 pm

I am helping a friend get his Elan Sprint back on the road after 3 years layup.
It starts instantly and runs well until hot, as it gets hotter it stops pulling then misses and eventually stops altogether.
when it runs it seem OK but will not pull.
I think it is the electronic ignition (it has a new coil) other opinions say the carbs or petrol.
Why is it OK cold but not hot?????
My plan for next weekend is to fit my carbs and if not fixed change the distributor back to points.
Any suggestions greatfully received.
cheers


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PostPost by: type26owner » Wed May 11, 2005 10:41 pm

Are the carbies getting hot to the touch? What type are they?
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PostPost by: wobblyweb » Thu May 12, 2005 3:12 pm

Hi
The carbs are Webers and are not hot.
What are you thinking??
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PostPost by: type26owner » Thu May 12, 2005 4:11 pm

That the mixture is about 20 to 1 and there's not enough cooling from the fuel vaporization to cool off the carbies so they heat up until the fuel boils. Once the fuel boils in the fuel bowls it will die. Too bad cuase that's easy to fix.

Let me give you a little tip here. Don't just assume it's caused only by a heating effect. If you fixate on that theme only you could blow right past the real problem and not recognize it.
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PostPost by: types26/36 » Thu May 12, 2005 4:37 pm

Rae,
I dont think you should automatically assume the problem is with the the carbs or fuel system, electrical faults can give strange results partically with bad earths (ground)
The Sprints have an alarm/imobilizer system with a switch in the glove (cubby) box, although I have never had a problem apparently the system gives lots of problems and I believe mainly when hot. From what I have heard people dissconnect or bypass the system but dont ask me how to do it as I have not had to. Shouldn't be too difficult though, anyway the point I'm making is check the electrics before you start pulling off carbs etc.
Brian.
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PostPost by: type26owner » Thu May 12, 2005 7:15 pm

Brian is absolutely correct in what he says. There is an established order for diagnosing problems like this. It's driven by the time needed to do the actual testing. Normally the order to follow is compression then spark and lastly pursue the air/fuel mixture. To check the compression and spark takes just a few minutes to eliminate those as being faulty. That's why they're always done first.
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PostPost by: rickf » Thu May 12, 2005 8:09 pm

A bad coil will often fail when hot. Try subbing it with another one.
Cheers,<br>Rick<br>1972 Elan +2
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PostPost by: storrar54 » Fri May 13, 2005 12:54 am

I agree with rick, I seem to remember a story about an elan stopping when hot and the cause was the lower radiator hose touching the coil and overheating it. Sorted by moving coil to cooler location.
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PostPost by: wobblyweb » Fri May 13, 2005 10:22 am

Hi everyone,
thanks for the suggestions .Its not the coil, I tried mine and it wouldnt start then realised his is a balast resistor type, I guess for the electronic ignition but anyway we fitted a new coil and no difference.
Compressions are inconsistant (cant remember what) Spark gets weaker and weaker when hot.

This weekend we will have another try. All I can think is to fit my Dellortos, then go back to points just to eliminate these.
I will check earths etc. first....
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PostPost by: brassrngfm » Fri May 13, 2005 6:28 pm

Ah ha! You gave another clue when you said ballast resistor! Check or 'chuck' the ballast resistor. Old ones can look fine externally and fail internally. I've had many similar vintage TVs fail that way on their power supply. New ones are cheap and can be had at any good electronics store. I hope that works for you. Check resistance of the resistor when the engine fails. I'll bet it's an open circuit!
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PostPost by: wobblyweb » Sat May 14, 2005 9:20 am

brassrngfm

where is the balast resistor???? I thought it was just the name of the coil!!
If we have changed the coil does that mean we have changed the resistor or not ?
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PostPost by: types26/36 » Sat May 14, 2005 9:32 am

Rae,
I didn't know Sprints had ballast resistors, I thought it was only on +2's. Sometimes coils are marked "use with ballast" why do you say it has a ballast resistor? you can check if the power feed to the coil has 12volts, if so it does not have a resistor.
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PostPost by: wobblyweb » Sat May 14, 2005 10:59 am

Hi Brian
We tried my standard Lucas coil and it would not start then took the coil to a motor factor who siad it was a balast resistor type and sold us a new one, the car does have electronic ignition fitted.
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PostPost by: types26/36 » Sat May 14, 2005 11:29 am

Rae,
As I said, test the power feed to the coil, if there is a ballast resistor in the circuit it will only have + - 8 volts and in that case there should be another wire coming from the starter, this wire will have no power untill the starter is turning and then it will deliver 12 volts. This "by passes" the normal circuit to boost the power for starting.
I do not know it your electronic ign needs 8 or 12 volts to function and maybe reverting to points is a good idea but you must also establish if a ballast coil is required as per 12 volt test.
I have only ever seen a ballast resistor on a Lotus (my Europa) and it is fitted on the coil,a round block about 1/2" in diameter.
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PostPost by: Frank Howard » Sun May 15, 2005 3:58 pm

I had the round block (about the size of a U.S. quarter) ballast resistor on my Europa and it failed. I replaced it with a standard ballast resistor that is found on most British cars INCLUDING MY ELAN S4. This resistor is a white rectangular insulator with a wire in it. The factory coil on my Europa is made by A.C. Delco (General Motors), so the proper ballast resistor is one of the easiest parts to find. I took the coil down to my local NAPA store and picked up a ballast resistor specifically made for G.M. resistor coils for about $5. They had them for Ford and Chrysler also. Hope this helps.

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