Lotus Elan

struggle to accelerate

PostPost by: checkrail » Mon Jul 20, 2020 1:16 pm

Hi, After all the ignition/timing problems with the +2, this is where I am:

Running with new points, condenser, red rotor and resister coil
static timed with lead light.
Been over the Webers with Synchrometer and Colourtune new plugs
Starts first time hot or cold, idles perfectly.

Anything above around 2000rpm it struggles, missing and jerking.
I had a plug lead shorting, thinking that was the problem so fitted new set of silicone leads but no difference.
Looks like I will have to try and find a mobile 'old school' guy, I really don't want to drive it far it's bad enough taking it round the block.

Once again any help please, thanks John P.S. have tried a different coil
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PostPost by: elans3 » Mon Jul 20, 2020 3:56 pm

Potential issue is the idle jets, as around 1750 - 2250 the fuel changes to the progression circuit.
What idle jets are you using & are they clear ?
Also check the accelerator pump jets, they can block easily. They will be either 35 or 40's.
Best way to check them is to take them out, clean them of any petrol, then blow through from the top, making sure to cover the side hole with your lips. With the jet hole at the bottom pointing straight forward, you should be able to feel air hitting you on the end of your nose. If it doesn't, it's blocked. Check all four like that. Doesn't take a lot to block them.
With either of these issues, the car will start ok and idle. The idle jets only show whether they're blocked when the progression starts, and the accelerator pumps when you put your foot down on the accelerator.
If they turn out ok, and the carbs were ok before, it will be electrical, or an inlet air leak.
I had a similar instance on my second S3 Elan, couldn't get it to run properly. Turned out to be the vacuum line from the inlet manifold to the headlights.. It had a defective one-way valve, so was sucking air into the inlet. Took me ages to find it, fitted a new valve and it was perfect .
Elan S3 SE S/S
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PostPost by: sprintsoft » Tue Jul 21, 2020 12:21 am

Hi John, has the car run 100% correctly since you removed/replaced the head?

I’m thinking your issues could be related back to that time

Iain
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PostPost by: checkrail » Tue Jul 21, 2020 2:36 pm

Thanks for all your suggestions, after the head removal / replacement the car ran perfectly other than the idle had speeded up slightly, I was looking into that when I left the ignition on and that was the start of all the troubles.
I had recently replaced the 'T' piece on the front cross member, the headlamps raise quickly.

I have found a contact for a mobile electrician but he has a two week waiting list, the good news he's worked on Lotus.

John.
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PostPost by: wotsisname » Tue Jul 21, 2020 2:50 pm

although it might be visiting old ground.. if not already, have you checked the little carbon brush in the top of the distributor cap... I had something a bit similar with an Elise (K series) and the brush was pretty much worn out...
best of luck.. you will get this sorted !!
1968 Elan plus 2 - project
2007 Elise S2 [modified with a Hethel 70th sticker (yellow)]
2000 Elise S1 - Sold
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PostPost by: sprintsoft » Tue Jul 21, 2020 3:01 pm

John, I would also test hot wiring the feed to the coil to eliminate any issues with the low tension wiring in the loom or a dodgy ignition switch.

Connect from a live feed on the solenoid direct to the +ve coil terminal, start it, drive it, and see if there is a difference.

NB Do not leave the connection in place once the engine has stopped.

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PostPost by: SENC » Tue Jul 21, 2020 3:28 pm

Have you checked the dwell? I'm wondering if some combination of weak coil, poor/high resistance connection, and/or incorrect dwell are limiting spark at higher rpms.
Henry
69 Elan S4
65 Seven S2
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PostPost by: checkrail » Tue Jul 21, 2020 5:57 pm

Iain, That's exactly how I have the wiring at the moment also with the yellow resister wire from the solenoid connected to the + terminal on the coil.
Once it fires I 'm wondering if the voltage is not lowering as it should using the resister circuit, and is causing the coil to misfire because it's running on 12v. I always use the battery master switch when the engines not running.
When the Igniter was fitted it had a red lead connected to the + on the coil and still the resister one, after all this time I realised that I've never had a 12v wire from the solenoid to the coil only the resister one.
I do not understand how the coil got it's 12v power from to fire the engine.
The dizzy cap is a quality looking one not the usual cheap and nasty sort.

John, having some very senior moments!
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PostPost by: Craven » Tue Jul 21, 2020 7:47 pm

Usually the solenoid used with a ballast system has an extra connection dedicated to supply 12 volts direct to coil, arrangement can vary, and that is only there in the crank situation. When the ignition key is released back to normal run voltage is supplied to the coil via the ballast resistor. You should find a diagram of how this is achieved with a search.
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PostPost by: sprintsoft » Tue Jul 21, 2020 10:29 pm

John, can you show us a pic of the top of your coil showing the connections, and a pic of the solenoid so we an see what’s connected where and verify the presence of any ballast.

Thank you
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PostPost by: checkrail » Wed Jul 22, 2020 2:50 pm

Iain, I'm afraid my computer skills are very basic and cannot send a photo.
The best I can do is as follows:
The solenoid viewed from above, battery terminal on the left starter motor on right.
The starting terminal on the left is where I connect a wire direct to + terminal on the coil,
this is the only way it will run but of course with all the misfiring.
The starter signal terminal on the right has the original yellow resister lead connected to the other + terminal on the coil.
There is a blu/yellow wire connected to the solenoid battery terminal that goes into the wiring harness. I cannot find that on the wiring diagram, but it looks original.
The negative on the coil goes to the dizzy as per normal.
I found a spare terminal on the ignition switch red/white wire and tried connecting to the terminal again on the solenoid, it ran worse than ever.
I hope that you can follow this and thanks for your patience John
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PostPost by: Craven » Wed Jul 22, 2020 4:11 pm

Pic of solenoid as used for ballast coil, note the terminal marked Power While Starting, do you have this terminal on your solenoid. Using this pic terminal designation titles say which of your wires are attached to each.
ballast solenoid.jpg
ballast solenoid.jpg (99.15 KiB) Viewed 199 times
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PostPost by: checkrail » Wed Jul 22, 2020 5:34 pm

Yes this is exactly the same, purchased from the same supplier as well.

Power while starting connected to + on the coil, Starter signal, existing yellow resister wire also connected to + on the coil
As I said in my previous post tried a wire from red/white terminal on ignition switch instead, but that was worse. Where can I connect to get power to the coil?

Thanks John
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PostPost by: sprintsoft » Wed Jul 22, 2020 6:25 pm

‘Starter signal should not be connected to the coil at all this is the signal from the ignition switch.
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PostPost by: Craven » Wed Jul 22, 2020 7:56 pm

Power while starting to + on coil correct.
Yellow resistor wire to + on coil correct.
Starter signal should have red/white from ignition switch crank position only.
Now the other end of the resistor needs a + 12v feed from the ignition switch normal run position
Blue/yellow wire. This Blue/yellow wire is not connected anywhere other than the resistor. How this physical join is made I don’t know.
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