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Help with problem


Mike6

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It still could be a carb problem such as a air leak on the inlet manifold leaning the fuel out under load or a combination of air leak and accelerator pump problem.

 

If you remove the inlet plenum cover and look down the carb barrels every time you open the throttle to say 3 quarters open a healthy jet of fuel should be seen squirting into each barrel as you turn the throttle lever.

 

Have you replaced the rubber carb mounting O rings at all? A good check to see if you have an air leak is to spray easy start around the suspected area and see if the revs pick up. (If you do this have a fire extinguisher handy in case of a stray spark).

 

Good Luck 

 

Cheers Mike

Edited by G_Reaper2
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If a valve was sticking open, the noise as the cam follower clattered about would be horrendous. This will turn out out be some footling little thing....fun is finding it. Engines need the right mixture, compression, spark and valves opening and closing at the right time. That's about it. It's going to be something you are SURE is right....but isn't. Those are the most infuriating...don't give up!!!

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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sounds like you are having fun yet another opinion for you if it pops in exhaust when missing its unburnt fuel in exhaust being ignited as combustion gases ignite stored fuel this is usualy an electrical unit breaking down it is sometimes possible to tell how many cylinders are involved by harshness of misfire will maybe show on kilovolts on scope but may need to be under load.The root cause is probably condensation from changing hoses and run up (no such thing as a coincidence) even when water has gone a track mark has still been created by ignition voltage (will look like a pencil mark on plug or cap or coil or inside plug lead) and ignition voltage will always follow easiest path, plug electrode path tends to be missed for preference of track mark under load check or replace all the units which handle high voltage

 

regards duncan

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Tried Andys idea of disconnecting the vacuum advance and retard pipes and plugging them. Car started first time, revved nicely and ticked over rock steady. Let it warm up checked timing was spot on and took it out on the road. Zilch, as soon as you try and pull away the revs die to nothing but tickover prevents a stall and I limp back with virtually no throttle.

Not sure about checking for a sticking valve as stationary you can rev the nuts out of the car and no strange noises.

Also, if it was a carb problem wouldnt it show up revving the car above 3000rpm at rest.

Rechecked the front end where I replaced the hoses  and nothing there that might be affected by leaked water.

To recap car was running fine before changing front hoses but I did fluff a gearchange after which the problem started - what could possibly have broken under load in these circumstances?.

 

Dicount dissy,cap, rotor arm, plugs and leads plus fuel pump, filter and regulator as these have all been renewed.

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  • Gold FFM

Four months of fannying around you still haven't found the original problem, Mike. That's impressive, because I'd have set fire to it by now.

Just a thought, have you considered taking the car to a rolling-road dyno place that knows what they're doing with twin Dellorto carburettors?

Margate Exotics.

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Perish the thought of a professional looking at the car :lol:

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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disconnecting vac unit is like you taking a kilo of valium as piston speeds up burn sequence has to start earlier in order to maintain power within downstroke all you've done is put it to sleep put vac back and run it again to see if its popping in exhaust if it is its losing ignition have cap rotor plugs leads coil all been replaced previous to hoses or after, didn't mean direct water contact meant condensation which forms on plugs and in cap when steam from run up is introduced .if you floated a valve on missed gear change you bend it not buckle stem unless valve head is totally parallel in its relation to piston crown if valves are at angle to piston crown and you had over revved you would have lost a compression you need to clarify what it does hot cold partload full load etc

 

good luck

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Think I have just lost confidence in this car which is why it is taking so long to fix. Over the years I have done a huge number of jobs on the car all of which have involved a lot of contortion and age has simply caught up with me. Yes I am stubborn and dont like the idea of handing my car to someone else particularly as I dont know anyone trustworthy enough near me - I have seen jobs so called professionals have done!.

Fannying around is probably a good description but I have sought advice from PNM and had an autoelectrician in. It is probably something simple like blocked carbs but I lack the enthusiasm to tackle this although I did buy an overhaul kit recently.

Even with the car running when you have lost confidence it is time to call it a day, so I will be putting it up for sale shortly.

Thanks for all the advice. 

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disconnecting vac unit is like you taking a kilo of valium as piston speeds up burn sequence has to start earlier in order to maintain power within downstroke 

 

No. Disconnecting vac was a logical troubleshooting step. The engine gets the operational advance it needs from the centrifugal advance weights. The Vac advance/retard does not come into play when hot and disconnecting it ensures its not incorrectly causing any advance/retard when it should not be.

 

I dont think we have had any confirmation though that the timing is correct at 3500 RPM. Is it?

 

The problem with these car-forum diagnostic threads is the replies from the person with the issue are often vague and miss out information and this is likely no exception, which is why it might well be time for a professional to look at it.

 

An example of this was recently on Ferrarichat there was a thread which lasted several months about a problem with "lack of power and poor acceleration". The whole ignition system was replaced, everything checked and double checked, but in the end it turned out the poster had missed out the vital information that when accelerating the RPM was shooting up without the cars speed increasing and the problem was in the end slipping clutch which could have been diagnosed instantly either by a pro looking at the car or on the forum if all the relevant info had been provided. 

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If the chap didn't realise his clutch was slipping, then there is no hope for him.....

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I would be looking at the carbs. Sounds like potential dirt issue possibly blocked progression holes/jets/ accelerator pump. The carbs/engine work completely differently under load, very little fuel is needed to rev an engine not under load.

 

Engine runs fine at idle and stationary tends to suggest the middle range of the fuel supply is being leaned out and then when you release the throttle fuel supply returns on the over run causing popping in the exhaust.dirt/gum can block jets etc at any time the timing of this problem starting could be coincidence.

 

Bent valves etc would show up on a compression test..

 

I hope you get it sorted soon. 

 

Cheers Mke

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Since its disconnected I will recheck timing at higher speed. Since I go on hols in a couple of days is there any mileage in putting redex directly into the float chambers to remove any crud (jets have been cleaned) and then giving the engine a blast though when I get back.

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How old is the fuel Mike?

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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I know you have cleaned the jets....have you measured the hole diameters?? Mine had a build up of varnish which wasn't apparent until I poked a piece of steel wire of the correct diameter into the jets...and it wouldn't fit. Need to find a suitable piece of wire... I used an old guitar string which I calibrated with both a micrometer and a digital vernier caliper. Once the jets were bereft of varnish and the correct internal diameter, all my problems were cured.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Fuel - filled up last time car on road in April

Jets - took them all apart and used wire brush strand as recommended by Dave at SJ sportscars so all clean when put back - they were a bit dirty

Timing - Andy with advance/retard blocked off on vacuum pipes ran engine until hot and than moved revs up to 3500rpm. Timing marks on flywheel via strobe moved to right as viewed so progressively moving more btdc than before. Is this correct

Tickover rock steady not missing a beat but as throttle moves up to 3500 rpm engine not happy at all and started backfiring and stumbling but as soon as throttle released back to nice smooth tickover.

Nothing to loose so imagine next step is to remove cam covers and see if there is any evidence of problems there.

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See if you can get some of the fuel out and compare it to new fuel, eg pop some into a pyrex jug next to some fresh fuel and compare them. If your old fuel is much darker, it's gone off and causes half the symptoms you're having (eg lack of power but ticks over fine). Admittedly 3 months isn't that old but if you used a high ethanol content fuel, it could be oxidised and full of water etc.

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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  • Gold FFM

Mike, before you sell it, have you got the factory timing figures? If so, good.

Disconnect the vacuum advance, and plug it at the engine end, it's not material for the test.

Check your timing at idle using the strobe, and also when Lotus says the timing should be all in, ie full centrifugal advance. Simply saying it moves to the right is not good enough. We need to know what the maximum mechanical advance in degrees is as indicated on your flywheel. If you can't see it because your eyes are not good, then get someone who can to do it.

Then post the results here.

And reconnect/unplug your vacuum advance when it's done.

Margate Exotics.

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Ian

There are only a few markings on the flywheel so no way to get any reading in degrees but it went past these fairly quickly by a fair amount - I would guess 40 degrees btdc. 

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just looked at your location too far for me why don't you ask someone to come and have a listen. sometimes 2 heads are better than one, before you start removing stuff. I would of had a listen if you where near me haven't done anything except marine diesels for 16 years but I served my time on this kinda shit would only of charged you a pint of guiness and a bag of dry roasted peanuts if I found it surely there is someone near you who can have a listen

 

good luck

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  • Gold FFM

Ian

There are only a few markings on the flywheel so no way to get any reading in degrees but it went past these fairly quickly by a fair amount - I would guess 40 degrees btdc.

Ok, I tried.

Good luck with the sale.

Margate Exotics.

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Timing...I go back to one of my previous suggestions. Sod all the measuring, turn the distributor back and forth until she sounds right. Then see what happens....turn the thing until it sounds wrong, then back the other way until it again sounds wrong. Stick it in the middle...pragmatic test, for sure, but I have known timing to be set incredibly accurately and be all wrong, as some factor has been overlooked. If you end up in the same position the distributor started out in, then it's a fair bet that the timing is right....but you may find that you set the engine free!!

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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There might be no problem wiith your carbs even just an inlet manifold air leak. A good test for air leaks around the inlet manifold & carbs would be to spray easy start on the inlet manifold joints and the inlet spacers etc if revs pick up the inlet manifold and mounting plates are sucking air in (make sure you have a fire extinguisher handy easy start is evil stuff).

 

Cheers Mike

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