Lotus Elan

Car running a little strangely

PostPost by: Rob P » Fri Jul 10, 2015 3:13 pm

Guys looking for advice. Car starting running a little poorly when put under load when running in top gear. Accelerating under normal conditions isn't what it used to be but isn't as bad as when dropping the accelerator when in top gear.
I have in an attempt to cure this done the following
Checked timing - Looks good
Replaced the following
Dizzy Cap
Plugs
Points
HT Leads
Rotor arm
Coil

Car is running strombergs and therefore not a lot of adjustments I can make on these I believe. only change I did make to these was to go from the twin choke cable arrangement to choke only on one. Car starts OK and runs ok on tickover but issue only becomes apparent when engine has warmed up and when trying to accelerate from a decent speed already, pulls ok from lights etc in first and second.

starting to feel a bit weird now as running out of ideas, possibly need the Carbs checking over? is that something I can do myself?
car did limited mileage per year before I bought it so wondering if there are other items to change which might be failing due to lack of use
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PostPost by: Spyder fan » Fri Jul 10, 2015 6:29 pm

Sounds like the dash pots need topping up with oil, that's the normal cause of the symptoms you describe on an otherwise ok running car.

Strombergs are pretty simple to maintain http://www.howacarworks.com/fuel-system ... arburettor
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PostPost by: vincereynard » Fri Jul 10, 2015 10:16 pm

Next step is to check the diaphrams. Even a tiny hole can effect throttle response.
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PostPost by: Galwaylotus » Sat Jul 11, 2015 9:30 am

Check for vacuum leaks. Are the carburetor mount O-rings intact and are the gaps adjusted correctly?
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PostPost by: Rob P » Wed Jul 15, 2015 11:14 am

Thanks for the feedback guys, managed to get back to looking at the car yesterday, dashpots were low on oil so topped up and took her for a little drive, issue is still apparent

I am assuming that checking the diaphrams and the O rings will require the carbs off the car.

I was also reading about not having the carbs fully tightened to the inlet manifold, the nuts on mine are very slack indeed, Tightened them slightly (the lower nuut on the inside carb was a pig to get to but a cut down spare spanner did the trick. Took the car out again and still not running great once over 3500 revs :(
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PostPost by: twincamman » Wed Jul 15, 2015 12:25 pm

OK ..I dont use thackery washers I use split washers 2 a stud they dont back off and are cheaper and easier to get .I also use nylocks on the carb studs and have no air leak problems at all?..ever ?.ed
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PostPost by: vincereynard » Wed Jul 15, 2015 12:59 pm

No need to remove carbs. Just the 4 screws holding the dashpot on.

See the image at the site provided by Spyder fan.

Lift off dashpot carefully. Remove spring and ease out damper rod / /diaphragm / needle assembly.

Screws might be tight!
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PostPost by: Spyder fan » Wed Jul 15, 2015 1:28 pm

Hi Rob,
here are my ravings/thoughts about your problem, the first is more of an observation: the second is probably worth looking at.
1) Reading your original post again, I notice you mention that you have disconnected the choke control on one carburettor but left it on the other.
I'm now wondering if you need choke to start the car? If so you will have 2 cylinders running on an enriched mixture and 2 cylinders on a lean mixture until you reach warm up. "Yes obviously" I hear you say, but you are most likely unduly fouling the spark plugs on 2 cylinders.
But, you say that you have replaced the plugs, therefore it's unlikely plug fouling is the cause this soon after you have swapped them.

2) You state the car pulls well in first and second, so I am inclined to dismiss the diaphragms or dashpot oil as the source of the problem and would look at the airbox and air filter assembly to ensure all is correct (clean filter, trunking intact etc) check the airbox backplate is sealed and connected securely to the carburettors and that nothing is obstructing the inlets to the carburettors.

3) If nothing is amiss, then it's time to start checking the diaphragms, this is pretty simple to do with the carburettors fitted in the car, read the link I posted in my first reply.

4) Still no cure and it's time to move onto the flexible carburettor mounting, change the O rings , and set the gap to .070 in or 1.78mm. (You state that you tightened the nuts, best to get a feeler gauge in there to make sure you haven't overtightened)

This is all stuff that you can do yourself cheaply and easily and hopefully you will find the cure amongst it if you go through it methodically.



Y
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PostPost by: Rob P » Sat Jul 18, 2015 10:01 pm

Thanks Alan,
Spent some time with a friend this afternoon working on the car. Checked the diaphrams and they are pretty new and certainly no issues with them, dashpot checked and oiled to the right level.
Plugs checked all round and despite choke being on 1 and 2 cylinders all plugs are fine.
Revisited the timing as my friend wanted to see if that was as I had said and that was OK.
O rings checked and no leaks apparent.
I have also now fitted a Cliveyboy K&N Filter with new pipework to the Air box so that should be OK

Couple of things to note today, firstly developed a petrol leak from the T piece between the Carbs, not sure how that occurred but the plastic T piece split at the join so have had to rig up a temporary fix. Anyone know if this part is available from anywhere or can advise on an alternative option, Braided hoses etc.
IMG_1460.JPG and


Also having issues with the Battery not holding it's charge, I don't suppose this will have anything to do with the original fault but a new battery will be purchased tomorrow.

Fault is still apparent :(
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PostPost by: Spyder fan » Sun Jul 19, 2015 7:52 pm

That's a shame that the simple stuff doesn't appear to solve the problem :(

Lack of pick up or acceleration can be pointed at two things mainly. One is lack of ignition advance and the other is fuelling deficiency.

On weber carburettors simple things like non sealing pump jet washers can give the symptoms you describe, on Strombergs it's the diaphragms or the dash pot oil level that are normally the culprit. So maybe the next item to look at is the distributor and check that it is functioning correctly.

I will stop at this point and ask for those that have more knowledge than myself as to how to test or check the distributor to ensure that it is working correctly. I will point towards this being a Stromberg carburettor Elan that requires a different advance curve than a weber carburettor Elan.

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PostPost by: Galwaylotus » Sun Jul 19, 2015 8:04 pm

There are distributor test machines around that will allow plotting of the actual advance curve. The other option is to use a programmable timing light and check the advance at various rpm to plot the curve.
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PostPost by: Rob P » Sun Jul 19, 2015 8:31 pm

Cheers Guys, appreciate the continued guidance, I have purchased a electronic points to replace the manual points so might try adding this into the mix this week.
Also borrowed a gizmo for checking the balance of the carbs so will also give that a whirl, need to swap the battery as it's really not holding any charge so a new one will be picked up.

I wonder if the issues I'm getting are due to the car having had so little use over the past few years and I have been really getting some useful miles on it since I purchased it?

Still love the car just know I shall have to work my way through the little niggles and clean it up as I go along :-)
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PostPost by: Rob P » Fri Aug 21, 2015 12:45 pm

Thanks to all for the info supplied, having worked through a number of the suggestions the car is now running beautifully. Finally nailed the timing which seemed to have become rather retarded, also had issues with the Distributor kicking out whilst trying to complete the setting which may be why it slipped out of timing in the first place.

The good thing is that the clamp is now secure (not over tightened as warned not to do by people on here) Coil moved to a better location for ease of access, new petrol lines fitted to replace the faulty T pipe between the carbs. New points, condesor, rotor arm, dizzy cap so a lot of new stuff in place which should all be helpful in giving me a few months of trouble free running

I live in hope. Thanks again for all of the useful guidance along the way 8)
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PostPost by: Spyder fan » Fri Aug 21, 2015 6:29 pm

Rob,
That's a great outcome, thanks for letting us know. Happy motoring
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PostPost by: Rob P » Wed Jul 26, 2017 12:12 pm

well it must be something about July with my car, strange running again but different to the original post but thought I would resurrect this rather than create a new post.
Car starts fine, runs fine for a while but intermittently will misfire and back fire with a loss of power then power kicks in again, this is usually after a period of spirited driving. On a couple of occasions the car has almost died but then suddenly burst back into life and can run OK for a few miles before problem starts again.

Have changed the points and checked the plugs for fouling and nothing seen there, dizzy cap and rotor arm look clean and clear of any wear or fouling.

Is this more likely an electrical problem as when backfire occurs there is a small flame suggesting burning off of excess fuel.
car is running old school Dynamo and points etc so nothing new in the way of electronics to consider. Any ideas to follow up on, I'll be back working through other parts at the weekend but thought i would solicit advice from the helpful experts on here in the interim
Thanks
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