Lotus Elan

Puzzled with really poor running Plus 2

PostPost by: Matt Elan » Sat Jan 06, 2024 3:45 pm

I've rewired my Plus 2 and am now trying to get her back on the road and I've experiencing some very odd symptoms. The car was running ok a couple of years ago when I started the rewire. I've got some type of electronic ignition (I assume pertronix) fitted in the distributor and I've got good feeds to the coil and distributor and good sparks at the plugs. The car is running(ish) on a pair of Dellorto DHLA 45s - the engine was tuned by Vegantune in the 1980s, petrol is new super unleaded Shell so no ethonal.
The car is a bit of a sod to start from cold, but using easy start type aerosol into the chokes it will fire up immediately. Once going it will restart easily but it will soot up all its plugs really quickly especially if the engine is under load - I'm getting through NGK B6ES types pretty quickly - and these are genuine items from a good source and are not internet fakes! Note that all four plugs seem to be sooting up at the same rate and the same amount
I suspect it is a carb issue, so checked the float heights - they were high so I've reset them back to where they should be, and resynced the carbs so they were in balance. The car was running ok on the drive and revving happily under no load, but going down the road the car missed badly on large throttle openings and I had to feather the throttle to get the engine to rev and pull - which it did on about 1/3 throttle. However very quickly the engine started to missfire and struggled to run and tick over. Getting the car back into my garage, I found that the brand new plugs were sooted up (again). The soot is very black and soft - plugs smelt of petrol.
A couple of other symptoms -
- This has been going on for a week or so, and on starting from being stood in the garage for a day after a previous days fiddling there is a fair bit of white smoke from the exhaust when the car first starts - I had assumed this was water vapour from the previous days fiddling about when the engine had been started, fiddled with, stopped, restarted etc. The while smoke disappears once the car was semi warmed up which sort of adds to the water vapour theory but may indicate I'm getting water into a cylinder (or two) from the cooling system when standing.
- after adjusting the float heights and rebalancing the carbs my colortune showed pretty much white (i.e. rich) on tick over but a healthy blue on revving (but of course this was not revving under load).
- there was initially a fair amount of blue smoke from the exhaust while trying to get the car down the road today, but it did reduce to virtually none by the time I got the car back into the garage; it did tend to do this before the rewire and I just assumed I had a bit of oil pooling in the head after running which was sucked in to the combustion chamber(s) and then burned off - when running 'normally' (or at least on the drive after staggering back) the exhaust was pretty much clear.
So, I'm thinking two (or three) scenarios in order of what I think is likely:
1. The sooting up of plugs is down to a fault in the carbs so the carbs need a good cleanout and service - but why both carbs and all four chokes are sooting up their plugs?
2. I've got a head problem which is pulling oil in to soot up all four plugs but again I'd expect one or two cylinders to be affected not all four.
3. Is the cylinder head failing and allowing some coolant to enter a cylinder?
4. Oil control rings are shot - but when I tested the compression I got an average of 190 psi (+/- 5 psi) on all four cylinders and again why are all four cylinders affected to the same degree?
I'm going to pull the carbs first and rebuild them with new seals, o rings, diaphragms etc - I did notice that no 4 cylinder's Auxilary Venturi was slightly loose which obviously isn't helping. Any other ideas from the collective?
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PostPost by: h20hamelan » Sat Jan 06, 2024 4:20 pm

The water level is decreasing?
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PostPost by: Matt Elan » Sat Jan 06, 2024 4:36 pm

Good call - the coolant level had gone down after this afternoons shenanigans.... so I suspect a leak from coolant into cylinders. Sniff tester ordered......
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PostPost by: 512BB » Sat Jan 06, 2024 4:40 pm

The first thing I would start with would be a good pair of 40 DCOE's or 40 DHLA's. 45's are far to large, even for most highly tuned motors. Its only a 1600 engine, not even that.

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PostPost by: HCA » Sat Jan 06, 2024 4:44 pm

I am not sure what you are posting! Are you asking for help or telling us what you have..?

I confess to only reading every third sentance, and can comment that your puzzlement should manifest into a lot of hard work.

Plugs sooting up - far to rich. White smoke - burning water, usually head gasket. Blue smoke - burning oil. Starts only with eazistart - carburettors (also harmful to the motor)

What more do you want to hear?
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PostPost by: Matt Elan » Sat Jan 06, 2024 4:56 pm

The car was running nicely before on the 45s so there is no need to change them :-) I'm petty sure Vegantune knew what they were doing back in the day....
I suspect there are a couple of issues here. On the strength of the water level dropping I'll pull the head next week and as they'll be off I'll strip and refurb the carbs as well.
Any other suggestions gratefully accepted!
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PostPost by: Donels » Sat Jan 06, 2024 5:35 pm

If you have a head problem you will be pressurising the water system and will see bubbles at the filler neck. Start the car and look before you remove the head, and check the expansion pipe to the bottle it will being blowing water and gas.

It would be very unusual for a water leak at the head to affect all cylinders so I doubt it's this and maybe you got convinced by white smoke and blue smoke. White smoke is common at this time of year on all cars upon starting, Teslas etc excepted.

It sounds more like a carb, plug or ignition problem. As noted black plugs show it's too rich, starting issues point to carbs but have you tried a hotter plug that will burn the carbon off?

You say you think it's got some type of electronics in the distributor. I think you should have looks what's in there and eliminate that first.

Head off is costly and may not be necessary, I suggest you do cheaper basic things first.
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PostPost by: mbell » Sat Jan 06, 2024 7:00 pm

First thing is do it's check all the jets in the carbs. Easy for then to clog up if left. A simple 10 minute no cost job....

The larger throttle opening suggests maybe a problem with the main circuit or could be clogged pump jets. So you get the same problems if you open the throttle very slowly?
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PostPost by: Matt Elan » Sat Jan 06, 2024 9:03 pm

I’ll do a sniff test before I pull the head but I’ll take the carbs off anyway and clean and refurb and check them anyway - it seems to be the most likely issue but watch this space.
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PostPost by: alan.barker » Sat Jan 06, 2024 10:42 pm

Hi Matt,
What Fuel Pump do you have and what pressure is it putting out.
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PostPost by: 2cams70 » Sun Jan 07, 2024 1:12 am

If the car was running well before you laid it up the first thing you need to ask yourself is what has changed in the intervening time? Do not dive into it willy nilly and start changing things on a whim before you properly ask yourself that question.

How long was the car in storage? Did you drain the coolant and fuel before you put it into storage? That's definitely one thing you should always do (coolant especially).
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PostPost by: draenog » Sun Jan 07, 2024 2:52 am

Have you just started to use super unleaded Shell? FWIW, I always used standard unleaded (E5) with a lead replacement/octane boost additive. With the introduction of E10, I moved to using super unleaded. My car has always had a propensity to soot up its plugs if idled in the garage for too long, but after moving to super unleaded it became much worse. It would misfire over 4000 rpm, gradually get worse, and I was often lucky to get it back home (if it stalled it wouldn't restart).

Of course, I carry several sets of spare plugs but it's not convenient to do a plug change stuck at a set of lights with nowhere to push the car (yes, I've been there)! No other difference, just the change in petrol. Using colortune showed it was running rich. I adjusted the carbs, and went too far. It ran OK but hotter than usual. A couple of 1/8 turn tweaks and it's been OK since.
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PostPost by: Lotus54 » Sun Jan 07, 2024 3:09 am

I would measure voltage when running (driving if you can) at the coil. Since the issue appeared to start after rewire, you may have a bit low spark under load.
Assuming a non-ballast resistor type coil, make sure close to 14V at the coil when running.

Certainly carbs may need a good clean- what chokes does it have? If about SE tune, 33mm seems to be a good starting point.
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PostPost by: draenog » Sun Jan 07, 2024 4:03 am

Sorry, the previous post has reminded me. It ran OK for a while but the high RPM under load misfire returned (but apart from that it was fine, no progressive misfiring until it stalled). I noticed the ignition coil was very hot. Replacing it fixed the misfire. I suspect, but have no proof, that the failing coil may have contributed to the problem I had after changing petrol...
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PostPost by: h20hamelan » Sun Jan 07, 2024 5:03 pm

2cams70
May I ask please. About your reasoning for coolant draining before storage.

I would guess the reason for not draining coolant would be for anti-rust, and any flake making its way into the radiator or similar heater-core passageways and maybe blocking/obstructing.

I use a conditioner with my coolant, in hopes of lubricating.
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