Before I get started ...........

[stuartgb100]

'71 Sprint with Webers.

Laid up the car in early December, and began an upgrade to the front brakes, using +2 discs, disc carriers and calipers.

Once everything was ready, it should have been straightforward ... but I forgot this was a Lotus. Suffice it to say, ( after ordering this, that and the other - and waiting for them to arrive ) that it was only this morning that I was ready to gently test it on the road.

Gingerley took it up the road. No obvious noises etc, so opened it up a little.

Horrendous backfiring, surging etc, but only under load. Struggled to get up even a gentle gradient. Limped back to the garage, and, embarrassed, hid from neighbours (vbg).

During the lay-up, the car was started every 2/3 weeks, run up to temperature, and then run for another 30 mins or so. Fuel in the tank is low, but the tank was flushed less than 1000 miles ago.

Car starts fine, but now I find it will not take any throttle, even after I returned to the garage today. So now it won't rev with any load.

I initially thought either fuel or (maybe) electrics. Now I'm thinking a fuel problem.

I'm pretty positive that during the lay-up period, I was able to rev it okay.

BTW, no other work was carried out during the lay-up, whatsoever.

Thoughts would be much appreciated, before I start disturbing things.
In the meantime there's the rugby........ it is a really nice day: had planned to video the rugby, take the car for a drive, watch the rugby later.
Bummer.

Should have known better !

Thanks,

Regards,
Stuart.

[Dave_Newcastle]

Stuart

Sounds like my post winter experiences of last year which I spent hours fiddling with carbs and plugs and ignition trying to eradicate.

In the end I came to conclusion that initial problem was any of or a combination of following:

- petrol "going off" over winter
- muck pulled through into carbs from low fuel level in tank (though filters were clean)
- something settling out of petrol and blocking fuel ways in the carbs whilst sat - my car is on dellortos and I have read on here somewhere that there is a theory that they are prone to this with winter standing (albeit I recognise that you have started you car from time to time with long running periods and you are on webers).

Anyway I dived in and regreted later on that I hadnt tried:

?20 of fresh new fuel and a good warm up and cobweb cleaning blast at 70 down the dual carriageway for good few miles.

Have you tried fresh fuel - nothing to be lost by diluting away your old stuff?

regards
Dave

[Dave_Newcastle]

repeat message deleted!

[john.p.clegg]

Totally off the top of my head but have you checked the auto advance is working and the bob-weights are not stuck?

John

[mcclelland]

Hi Stuart,

I must agree with Dave after having more or less the same problems. I would start with some fresh fuel, change the plugs and have another go!

I also notice you say that your upgrading the brakes to plus2 spec. I am about to do the same shortly, can you tell me how you find them as in one of the posts someone said he found it upset the ballance of his car so I would be most greatful for your comments.

Regards, George...

[berni29]

Hi There

Apologies for suggesting this because I am sure that you have tried...but have you made sure that the plugs are clean? I find that the garage running can really deposit a good amount of soot on them, and then leaving them for a while and repeating the process repeatedly can make matters a lot worse.

It is strange how you can leave an engine that has in the past run OK, and them come back and it is running like it comes from a different car. For a simple system it can be very complex to problem solve.

All the best

Berni

[stuartgb100]

Thanks all, for the suggestions.

Did not have much free time, but have removed the tank and flushed it. Refixed and partly filled it with fresh petrol. Cleaned the plugs.

It started first time (as usual) after cranking over to get fuel through. Same problems though, as soon as any revs are applied. Did a quick check of carb balance and mixture - no effect.

Did not really expect to find muck etc in the tank, since I drained, flushed and painted it last summer.

I guess I better look at the pump, and check out the float chambers etc, during the week. Better order up some carb gaskets pdq.

John - will check the distributor (albeit rebuilt a year ago) as you suggest, also the timing.

George - can only say that the brakes need yet more bleeding, so nothing to report at this stage.

Regards,
Stuart.

[Otto]

Hi I had the same problem. Mine was due to weak spark. I had some electric bad points to the coil. The engine worked perfect at low revs, but coffed and puffed and drowned at accelleration. Fixed the wires, and It workes perfect now.
Otto

[alaric]

Damp in the distributor? Poor earth somewhere? I agree with the previous post re a weak spark. But the weights being jammed makes sense too.

Hope you solve it quickly.

Sean.

[stuartgb100]

Thanks again for further replies.

Spent a cold two hours in the garage, and can give the following update:

Cleaned and gapped plugs (now getting very black after even minimal running). Ran up to temperature and balanced carbs. Set mixtures with colourtune. Checked timing and dwell. Advance appears to be working, but of course there's little to tell when revs are so low. It does advance, and then the misfiring occurs. So basically all there or there abouts.

However, no significant improvement

So I'm thinking as follows:

Fuel pump and float chambers (just to eliminate any question of "carp" in the fuel system).

Quality of spark (ie condensor, coil, points, and associated wiring, dampness etc).

BTW, the backfiring seems pretty arbitrary. Definitely not limited to a particular cylinder or carb. At least 3 ports were quite happy to spit at me.

Might try the 'tickover in the dark trick' tomorrow night, and watch the pyrotechnics for clues as to any changes when throttle is applied.

Regards and thanks,
Stuart.

[Frank Howard]

just to eliminate any question of "carp" in the fuel system.

Stuart,

This is a true story. I once stopped at a gas station and proceeded to wash the widows as I was filling the tank. While I was washing, I noticed a particularily foul odor. I incorrectly assumed it was coming from a nearby factory. When I went back to the window cleaner container to get more washing fluid, I realized what I was smelling. Someone had dropped a dead fish into the container as a joke I suppose, and now the entire car reeked.

So I can tell you from personal experience that Carp is not good for cleaning a car. I can only assume that it's not good for the fuel system either.

[Greg Foster]

I have always used a carp to wash my winshield. With Magnificent results! Ocassionally, if a Carp isn't available, I will use anchovies.
Frank did you see the results of using carp?

[stuartgb100]

Well, after another evening in the cold garage, it may be that all this "carping" is finally over.

And a rather strange culprit, to be sure.

I decided to check inside the distributor, despite dwell being okay. In removing the cap, I noticed the condensor was loose ! Given the lack of space, I removed the distributor. Here's what I found:

Clearly, at tickover, a reasonable earth was established. However, higher revs resulted in vibration, and a subsequent misfire.

Never seen this before.

Hopefully this solves the problem............

Regards,
Stuart.

[Frank Howard]

Poor earth somewhere?

Stuart,

Looks like Sean had it pegged. By the way, that condensor couldn't have been manufactured by the Prince of Darkness could it?