Help with problem

[molemot]

I'd be VERY surprised if an ultrasonic bath would get the varnish out of the jets. Mine certainly didn't do any good on my jets....gets the dirt off nicely but wouldn't touch the varnish inside the bore of the jets. Great things though...wish I had a really BIG one...(!) I still haven't found a solvent that touches the stuff...tried everything; acetone, cellulose thinners, MEK, Trichlorethylene, white spirit, all sorts.

[G_Reaper]

Just using a single solvent will not remove varnish in an ultra sonic bath. A combination is required hence detergent and and a mild acid I also used some degreaser in some of the baths then washed the parts down with carb cleaner afterwards. 

 

That worked for my S2 carbs which had stood unused since1986 and has worked on my 87 HC turbo. My Ultra Sonic cleaner is quite powerful and also heats the bath solution. Maybe this makes a difference? I will try and post some photos of before and after.

 

Cheers Mike

[molemot]

Acid....the one thing I haven't tried.....(!) Still, no need now and I've given up using the blasted E10 petrol so the varnish problem shouldn't recur. My ultrasonic cleaner gets hot, too....had loads of use last year on the boat carburetter, fetched the filth off nicely.

[Mesprit87]

Wonder what it could do to my injectors... keep us posted on the solution you use.

[Mike6]

Well I think thats me buggered for the Lotus meet at Weybridge. Car started first turn of the key a week after cleaning out the jets etc. Ticked over nicely on the drive and revved without problem but a short distance up the road it started juddering, lost power and limped back home. Almost everything has been replaced on car so at a loss how it was fine when I put it away in the garage to change a few front end hoses.

 

Will check a few more things just in case but now have booked a specialist mechanic to home visit next week. 

[molemot]

Fuel? Condensation in the tanks giving water in the petrol....always part of the daily inspection on a piston engined aeroplane, drain a bit off the bottom of the tank and check for water. The symptoms are as you describe, but the results are less readily dealt with!

[Mike6]

Fairly certain it isnt water in the fuel  as I cleaned out the carbs and jets including checked regulator pressure and checked for blockages by letting petrol pump freely out of the petrol lines. Today, decided to check for any problems inside the distributor cap but given everything was replaced 6 months ago nothing was found. Last thing I can check when I have reassembled plenum (which had a fair amount of fuel sloshing about inside) is to connect up a spare Ignition Amplifier as I am now becoming convinced its electrical rather than fuel. The Auto Electrician did mention however that its not unheard of for silencers to break up internally and block exhaust flow under load. 

[andy b]

Going back to the original post (problem) What ignition system is fitted to your car. I had a problem with my NA which has the constant energy system. it also has a vacuum advance for cold starting which advances the timing by quite a few degrees, When it warmed up this vacuum is cut off and you have a std advance curve relative to  revs.

My problem was a small brass contact inside the disi which rubs on the moving advance plate keeping it in contact and to earth.

My disi had a lot of oil inside and the contact failed the engine cut out (Only when it warmed up and the vac advance plate moved to normal running position) restart the car and it ran fine, Until it cooled and restarted the whole scenario again.

As you said it played up at the same place on the run it could be when it warmed up and the plate was returning to normal running.

How i fixed mine i made a flexible wire to earth the plate to body giving it a solid earth contact

This may help good luck andy 

[Mike6]

Thanks Andy, I do have the Constant energy system with both advance and retard vacuums. I think its a Lucas 45DM4 I replaced the magnetic pick up several months ago as the old one failed every time the car got hot. I have just rechecked that the pickup leads have not chaffed and all looks ok. I will mention to the auto engineer the possibility of internal failure of the distributor but it is all nice and clean with no oil contamination and I dont feel inclined to strip that lot down at this stage.

As an aside I had to chase out a mouse from the garage (its that time of year) and wondered if it or its mates had chewed through any cabling but all looked ok.

[andy b]

The bras contact connection is between the two  plates so you cannot se it until you remove the top plate.  

[Andyww]

Have you tried running the fuel pump with the engine not running and see if any fuel emerges into the plenum or the cylinders?

 

I know we have covered the fuel pressure already but might be worth double checking the needle valves are holding closed against the fuel pressure. If you have a lot of fuel in the plenum it sounds like this is happening.

 

If you have had a lot of fuel sloshing about you will need to check the oil level. Its very likely gone up owing to neat fuel draining past the piston rings into the sump. If its gone up substantially this definitely means the carbs have been overflowing. The oil will need to be changed of course if this is the case.  

[Mike6]

Thanks Andy will check all that in the morning. Luckily the cover is still off the plenum - I gave up for the day after refitting the dizzy cap and finding I had shredded my hands. I know petrol got into the plenum when the gasket didnt fit correctly on the float cover and everything flooded so assuming some was still in there a week later. The needle valves are brand new however.

[Mike6]

Well mechanic was here all day and tested everything and couldnt find a thing wrong. Half the car was stripped down over 8 hours. Car starts first turn, ticks over evenly and revs nicely etc etc but as soon as she warms up under load on the road it is all over the place. Given that I have spent thousands on replacing everything it is galling that under load she jumps about all over the place. The only possibility is it need a full carb rebuild rather than the jet clean I have done or one of the parts I have renewed is faulty, but how the hell  can you tell if a new part is faulty - I dont think SJs will admit to that. 

[molemot]

Faulty new parts....that's why it's always best to replace things one at a time. The "shotgun" system of rebuilding everything can cure problems...but accurate diagnosis will always be better. Change something...no difference...it wasn't that. Change something else and repeat. The sort of problem you have, which only happens after the engine has reached operating temperature, would seem to be due to the effect of that temperature. You could try cooling down various bits...a useful faultfinding tool in electronics, the can of freezer spray...spray it on a component, and if it fails (or starts working again!) you've localised the fault. Don't think the idea would help with mechanical stuff, but you could try it on the electronics....

Alternatively, it might not be temperature but time? Something works fine for a bit and then fails...

[Mike6]

Thanks John, wise words. The auto electrician phoned back this morning and said the one thing he didnt check was the cam timing and asked me to check which I have - all fine. Which I would hope it was !. Couldnt believe that he spent 8 hours here trying absolutely everything - even gave me a few shocks through the ignition system.

He suggested that the characteristics suggest a faulty distributor pick up which he tested at idle but are prone to fail under load. With postage and vat etc the last one cost nearly £100 barely six months ago. Will try and get one through Pete Musgrove at PNM in case the SJ ones are faulty.

[simon a-b]

Hi, I have had very similar issues to this one, (idle fine, run under load fine for a couple of Ks, then fail.  I think I've now got my issue isolated to the connections around the coil... Have you been through them all?  

 

I used some electronic cleaner spray (which also worked wonders on the window lift switches... I've go the relay mod fitted but one switch wasn't passing enough current for the relay, one spray and all good).  Give all the spade connectors a good spray, nip the females up gently with pliers.  Worth also looking at the plug between the dizzy and ignition module, this has been a point of failure too.  

 

Cheers,

Simon

[Andyww]

One difference between being under load and not under load, with same revs, would be the vacuum advance.  

 

When under load there is minimal vacuum. Is there a possibility that the ignition timing has been incorrectly set at max vacuum (ie at idle with the vacuum tube connected) so that when the vacuum is reduced it goes out of spec?

 

You could try disconnecting the tube and check the timing at idle and also make sure the mechanical advance is working by checking at 2500 RPM according to the manual.

 

Then leave the tube off and try driving.

[Mike6]

Thanks Andy and Simon. Fairly certain it isnt timing related but must admit didnt disconnect the vacuum tubing when checking. Car was running ok when last used and there is no evidence that anything has slipped. However cannot check now as distributor is about to come out of the car. When I spoke with Pete at PNM he said that the electronic pick up is obsolete but that rather than use an OEM version (a lot are dodgy) he remanufactures and thoroughly tests them. So going to send the unit to him today. 

Will then reset timing as per your recommendation.

[Andyww]

If the timing was "correct" at idle with the vac tube connected it will be miles out under load. Could well be the problem.

[Mike6]

Having received back my remanufactured distributor and new rotor , dissy cap, plug leads and plugs from PNM engineering, I decided to have another go and get it working. I took my time and rechecked everything was ok including cam timing and initial distributor timing by the book. The car started and ticked over but as soon as you  touched the throttle the revs dropped and she wanted to backfire but didnt have the energy before cutting out. I again swapped over the coil and spark amplifier but no difference.

Have completely exhausted everything I can think off. If anything it is worse than before when it wouldnt run under load but revved freely sitting on the drive.

Any out of the box ideas more than welcomed.

 

Thanks

[G_Reaper]

I would try another coil. There is not the quality control on old style parts there used to be, I ended up buying 3 before getting a good one that did not fail after initial warm up.

Check your ballast resistor if fitted.

 

Good Luck

 

Cheers Mike

[Sparky]

How did you time it initially?  Have you strobed it?

[Mike6]

Very strange but I marked everything up on the distributor before sending it to PMN. So when putting back I checked at TDC that it was pointing towards plug 1 and reconnected it according to the markings which seemed fine. I have just about managed to get the engine warm enough and then used a strobe - cannot even see the 10 degrees before white mark on the flywheel so timing must be out a fair amount. Will try adjusting the distributor according to the strobe rather than the original makings on the dizzy body.

[Andyww]

Note that its best to set the timing as per the book which specifies setting at 3500 RPM. The figure varies with version but is 28 degrees for distributors without vac advance. If you have vac advance you could leave it disconnected. 

[Mike6]

Andy

Dont think this applies to my early Stevens carb turbo. The book says warm engine and then set at tickover with advance connected.