Backfiring

[UAB807F]

Hi Randy,

I think your carb specialist is right, looking at that float mounting it might hold everything in place to check the float height out of the carb, but once assembled and with the force of petrol lifting the floats I could imagine it giving a higher float height in practice. And that's got to be a richer mixture if not flooding. But let's know how your repair goes, my carbs have the same split float mounts and I was hesitant when I changed the needle valves because it looks a weak design and too easy to snap off.

Another vote for the ignition coil/condenser as a next check. I've had them able to start the car but pack in when warm, then it would start but not rev and finally (after I hadn't taken the previous hints) it stopped working entirely.

Brian

[robertverhey]

Got some fine wire that you could temporarily hold the pin in place with (by twisting it around the pin and remains of post)? I'm not yet convinced.....

[bast0n]

Randy

I have had your symptoms before - more than once and each time it was the coil. Now moved to over my feet to keep it cool and no more problems............................yet!

David

[Sea Ranch]

Yes, great. Thanks for these insights.

I'm hopeful that I will solve at least some of the symptoms with this repair (pix coming tonight when I get home from work and install it), but not convinced either that repairing the float pivot will fix everything. But a little glimpse ahead: when I pulled all four plugs and looked in, cylinders 1 & 2 were wet inside and not so much cylinders 3 & 4 (this coincides with the goofed float in the front carb).

Robert, that's exactly what I thought of at first, but I've gone with a JB Weld (epoxy) fix as my first attempt.

Brian, beginner question: you say coil AND condensor (David mentioned coil). Do you mean the condensor inside the distributor cap? I have a solid state ignition installed (by PO). Is there a condensor in this system still? Or do I need to just buy a new coil only??

Thanks SO much, gentlemen. Will know in a few hours regarding the float fix (if the "weld" holds and what symptoms it alleviates).

Randy

[UAB807F]

Hi Randy,
If you're on a modern solid state ignition it's just the coil you need to look out for, I hadn't realised you'd moved away from olde-worlde contact breakers.

But given you've found a problem inside one of the carbs, I'd fix that and see how you go before buying another coil, just on the off chance that an over-rich mixture was killing the engine. The over-rich mixture might have been a variable thing with more revs pushing the pump more and maybe forcing fuel past the valve. (that's assuming you're still on the mechanical pump) A cold engine might handle this rich mixture better, a bit like using the choke, but the hotter engine would react differently.

Brian

[Sea Ranch]

Thanks for your interest and patience. Here's the run down so far.

No success yet. This evening I have:
- repaired the float pivot point, re-assemled float and re-installed.
- checked for spark at all four plugs - looks good
- re-made connections at coil
- checked fuel pump: it's supplying fuel to both carbs
- pulled top cover filter on each carb: fuel present (this is immediately after the banjo joint fuel intake on each carb)
- pulled top covers again: float bowl is at appropriate level

Still, I did not have one single combustion event this evening as I cranked it over (a lot). When I pull the plugs again, they are totally dry, as if there is no fuel getting to them.

So how can I have fuel present at the carbs and in the floats and yet have totally dry spark plugs? I don't get any combustion at all. None. Yet the plugs all have a spark when pulled and grounded to the cam cover bolts.

Here's my assumption: I do have spark but apparently no fuel is getting in. But why, I don't know.

I have no trouble getting another coil to install, but hesitate because it doesn't seem to be my immediate problem.

ANY thoughts welcomed I'm going to bed and sleep/think on it!

Randy

(some pix of the carb repair, for what it's worth . . .)

[robertverhey]

Good morning!

Hmm plenty of fuel to carby but none in combustion chamber..... Which points to jets or accelerator pump.

If it was me I'd

- check all the timings again (cam and distributor) Spark may be healthy but if at wrong time, car will crank away endlessly but remain dead as a dodo

- pour a bit of neat fuel down each spark plug hole, replace plugs and then see if there's any life. Just a couple of thimbles will do, and have an extinguisher nearby

- blow out all jets

- if all else fails, remove carb nuts and washers and pull back carbs until you can see down between them and tracts. Operate the accelerator lever. You should see a healthy squirt from each tube

[Sea Ranch]

Thanks, Robert!

Blow out all jets . . . how do you do this "in situ"?

[ardee_selby]

Greetings,

So I'm driving home from school/work and get within a block of my house when I've run out of power and, it feels like, fuel (am definitely not out of fuel, though).

It's now a struggle to get the motor started; it turns over without firing, then eventually starts up. Does not accept throttle well; you have to nurse it up to 2 or 3 thousand rpm and that's about all it will do. Further, it putts a bit and will occasionally backfire like I'm going to blow out/up the muffler.

There is fuel in the stock glass-bowl fuel pump. I pulled the filters out from under the large brass nuts on the top of the Weber DCOE40s but there was precious little foreign matter there at all. Turned over the motor to see if fuel was coming in - it is.

Randy

Randy, getting back to your OP, quote: "(am definitely not out of fuel, though)"

Had you , by any chance, just filled her up?

[UAB807F]

Randy, gee this one is a struggle. You've got a "Lots Of Trouble, Usually Serious" car all right, a real genuine Lotus !

To blow out the jets, yes you can dismantle from above and pull them out without removing the carbs. I forget where it was, but there's been a thread within the last few weeks about doing just that, complete with pictures. Found it - pictures down the page. Another Brian, "types26/36", has posted some good shots with "how to" notes.

elan-f14/tuning-t23441.html

Since you posted I did have another thought on the poor running - how old is the petrol ? I had trouble resurrecting my car from it's slumbers this year and it really wouldn't run. Filled up with fresh petrol and all was well, so it might be surprising just how quickly some of the components evapourate.

Finally, one trick I always do to start up after a layoff is to get an aerosol of what smells like ether, marketed here as "Quick Start" or "Cold Start". Pull off the air filter trunking and spray it directly at the trumpets. Turn it over with the throttles open and it always starts, sometimes dies away but then usually restarts without lots of churning away. If it won't start like that then I'd suspect an electrical problem or somehow you've managed to keep all the inlet valves closed at once !

Brian

[Sea Ranch]

Randy, getting back to your OP, quote: "(am definitely not out of fuel, though)"

Had you , by any chance, just filled her up?

So you've piqued my curiosity, Richard!! I did, as a matter of fact. Topped up much higher than usual, so that I could see the level in the filler tube. Never done that before, out of concern for spillage, but it happened. Are you suggesting some sort of venting issue? I had also temporarily plugged the two vent tubes (Plus 2) but then unplugged them.

Thing is, the fuel pump seems to instantly supply fuel on turn over, whenever I crack a joint to observe.

[Sea Ranch]

Thanks for your thoughts again, Brian, and the thread on Webers. That will be my next stop: study these things up and do some cleaning, as my initial thought was that I had ingested something into the carbs through the fuel.

And I will also try the fuel direct into the spark plug hole, or the spray starter, too. Have to find out if lack of fuel is the problem.

[types26/36]

With Compression, Fuel, Spark, Timing and the car should start, try adding a little fuel down the spark plug holes as suggested earlier, if there is still no signs of life get some one to place their hand over the exhaust outlet while the engine is cranked over to see if there is any pressure, although very rare a baffle can dislodge and block the system and it will never start.
Its worth a check.

[ardee_selby]

Randy, getting back to your OP, quote: "(am definitely not out of fuel, though)"

Had you , by any chance, just filled her up?

So you've piqued my curiosity, Richard!! I did, as a matter of fact. Topped up much higher than usual, so that I could see the level in the filler tube. Never done that before, out of concern for spillage, but it happened. Are you suggesting some sort of venting issue? I had also temporarily plugged the two vent tubes (Plus 2) but then unplugged them.

Thing is, the fuel pump seems to instantly supply fuel on turn over, whenever I crack a joint to observe.

Randy,
I don't know anything about the new fangled venting system on +2's. However, if the problem kicked in shortly after filling up, was it just a coincidence? I was wondering about possible fuel contamination...water in particular. Look closely at the fuel in pump bowl and/or float chambers for any sign of water globules. Can be hard to spot if your not looking for it.

I've had water get into carbs in the past (with other cars). It caused all sorts of weird symptoms. Hard to start, then f*rts and bangs, not unlike what you've described.
As Sherlock said - Eliminate the impossible ...whatever remains etc etc

(BTW: The most recent fuel contamination in the UK was silicones, which screwed the O2 sensors on modern stuff, which, in turn, b*ggered the engine management systems)

[billwill]

The one thing not mentioned yet that can cause those symptoms is a faulty rotor arm.

It can look perfect yet track through internally when warm.