Lotus Elan

Not starting- another sanity check

PostPost by: The Veg » Sat Aug 08, 2020 10:50 pm

I've finally got the engine back together and have been trying to start it to no avail. I suspect something ignition-related but could use guidance in case I'm missing something. Here are the relevant facts:

-Had no trouble starting a few months ago when I found the excessive oil leakage that prompted this latest round of engine-work. Valve clearances were mostly incorrect before but are now within tolerance.

-After re-assembling the valvetrain I thoroughly checked that the timing marks all lined up and continued to do so after lots and lots of hand-turning of the engine.

-Fuel is getting past the carbs, verified by sticking a finger past the slides (Stromberg) after some cranking.

-Spark is being produced, verified with a removed plug visual test.

-Battery is an Odyssey AGM rated for 330 CCA, tested good in a load-test at the auto store yesterday and was fully charged when tested.

-The primary weird symptom: with power to the coil disconnected the cranking is strong and eager and consistent, but with power to the coil connected the cranking sporadically becomes quite weak and barely turns over at random moments. This is true even when the jumper cables are connected to the huge battery in our Dodge Challenger (which is also boot-mounted, interestingly enough).

-No sign of any coughing, sputtering, or feeble attempts to fire at any time.

-Use or non-use of the enricher ('choke') doesn't make any difference.

-When it ran a few months ago the ignition timing had been static-timed to around 0 BTDC, to be corrected later but it still ran well. Before these latest unsuccessful attempts to start it was static-timed to 10-15 BTDC.

As I always ask, what am I missing here?
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PostPost by: SENC » Sat Aug 08, 2020 11:58 pm

Have you put your voltmeter to use testing sequentially along the ignition circuit to confirm you're getting expected voltages along the way?

I'd double-check grounds first. Did you reinstall the engine ground strap (I missed that for a long time once).

Do you have a ballast resistor and low resistance coil, or no resistor and 3 ohm coil? If the former, are both the bypass circuit and resistor circuit testing ok and when expected (bypass only when ignition is in start position).
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PostPost by: 2cams70 » Sun Aug 09, 2020 12:12 am

Did you replace the head with timing marks lined up AND with the engine set with number one piston at TDC?
Did you put the correct sprockets on each camshaft? The timing marks are in slightly different positions on inlet and exhaust
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PostPost by: mbell » Sun Aug 09, 2020 2:39 am

Points or electronic ignition?

Elec ignition can have issue if there too much voltage drop in the system reducing the voltage below this minimal operating point. I've had problem in the past but good cleaning up of grounds and other connections seem to have addressed it.
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PostPost by: The Veg » Sun Aug 09, 2020 5:16 am

Things I can answer right away:

-Yes, cams timed at TDC.The way my brain works, the mark on the crank pulley is one of three timing marks and all three must agree before I'll call the job done.
-Points, no resistor of which I am aware.
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PostPost by: 2cams70 » Sun Aug 09, 2020 6:44 am

Suggest you shine a torch down the spark plug hole when the camshaft sprockets are lined up to confirm the piston is where it should be.
Last edited by 2cams70 on Sun Aug 09, 2020 6:50 am, edited 1 time in total.
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PostPost by: Andy8421 » Sun Aug 09, 2020 6:44 am

The Veg wrote:
-The primary weird symptom: with power to the coil disconnected the cranking is strong and eager and consistent, but with power to the coil connected the cranking sporadically becomes quite weak and barely turns over at random moments. This is true even when the jumper cables are connected to the huge battery in our Dodge Challenger (which is also boot-mounted, interestingly enough).



One possible explanation is that the mixture is being ignited at the wrong point in the cycle, and the starter being asked to compress hot gas rather than cool mixture. Assuming you have got the static ignition timing right, have you got the right leads going to the right plugs? Even if you are putting the leads back onto the plugs they came off, it is easy with the skew gear drive on the distributor to put it back 90, 180 or 270 degrees out.
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PostPost by: Andy8421 » Sun Aug 09, 2020 6:47 am

2cams70 wrote:Just because you lined up the crank pulley mark does not mean the number one piston was at TDC. It also lines up when number one piston is at BDC.


I don't think you have that quite right.
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PostPost by: 2cams70 » Sun Aug 09, 2020 6:55 am

Andy8421 wrote:
2cams70 wrote:Just because you lined up the crank pulley mark does not mean the number one piston was at TDC. It also lines up when number one piston is at BDC.


I don't think you have that quite right.


Agree - edited! Spark plug wires theory sounds quite plausible.
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PostPost by: lotusfan » Sun Aug 09, 2020 11:37 am

Mr Veg

Is the distributor installed correctly? Have you removed and refitted it during the works you have carried out?

I ask because I have carried out some engine works recently and when I came to start the engine it would not start. Eventually I discovered that the distributor fitting instructions in the WSM are misleading and I had not installed it correctly.

My take on installing the distributor is as follows:
1. set engine to TDC with cylinder 1 at top of compression stroke. Cam lobes on cylinder 4 should be pointing at one another.
2. hold distributor with coil connector pointing towards front of engine, the cap retaining clips will be at 12 o'clock and 6 o'clock. Set rotor arm to 9 o'clock.
3. now insert distributor into engine, as the gears engage the rotor arm will rotate clockwise by about 45 degrees.
4. tighten distributor clamp lightly.
5. confirm rotor arm is pointing at No 1 plug lead.
6. set static timing to your setting of choice - 10 or 12 degrees BTDC. Tighten clamp.
7. pull out choke, turn key, engine bursts into life - hopefully.

HTH
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PostPost by: alanr » Sun Aug 09, 2020 12:32 pm

'2. hold distributor with coil connector pointing towards front of engine, the cap retaining clips will be at 12 o'clock and 6 o'clock. Set rotor arm to 9 o'clock.'

Not quite correct..Ok it will work that way but only if you personally or a previous owner have repositioned the spark plug leads in your distibutor cap.
Should be..
With timing set to TDC on No1 cylinder (Back two valves rocking, i.e Cam lobes on No 4 sloping towards each other).
The correct original distributor position should be, assuming the spark plug leads are in their original position in the distributor cap, will have the distributor clips at 9'oclock and 3 o'clock ( LT connector terminal in the 12'oclock postion)and the distributor when fitted will have the rotor arm pointing in the 10 oclock position with points about to open and fire No 1 cylinder. In other words the rotor arm position will correspond with No1 HT lead position in the distributor cap.

Alan.
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PostPost by: alanr » Sun Aug 09, 2020 2:00 pm

Just to follow on from repositioning distributor in last post..
Perhaps hard to understand but you will almost certainly have lost ignition timing ( Distributor position)when removing your head/chain/cams etc so that is why you need to start from basics and completely retime the ignition. i.e Reposition distributor base to correspond with No1 when on No1 TDC.

Hope this helps,

Alan.
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PostPost by: lotusfan » Sun Aug 09, 2020 4:13 pm

Apologies if I have confused the issue. Now I see that my distributor cap is not standard. With the leads pointing left from 9 o’clock the cap clips are at 12 and 6 o’clock.

However, from The Veg’s description I would go with spark in wrong place still.
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PostPost by: The Veg » Fri Aug 14, 2020 1:12 pm

Thanks guys, much-appreciated! I've been too busy to do any fettling since my query, but should be able to get on it during this weekend.
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PostPost by: Craven » Fri Aug 14, 2020 2:11 pm

Don’t think you mentioned your starter motor type, if you have the standard Lucas unit then with an advanced ignition they will simply refuse to go over TDC. Try taking the timing back to say 5 degs and try.
BTW my Porsche 911 static timing is 9 degs After Top Dead Centre.
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