free hit
counters
End of my tether! 86 S3 N/A - Engine/Ancilliaries - The Lotus Forums #ForTheOwners Jump to content


End of my tether! 86 S3 N/A


Recommended Posts

Hi folks, 

So i have a stumbling engine. It has always been the same throughout my almost finished rolling restoration. The thing is its only happens after about 15 minutes of driving, lasts for about 5 minutes then goes away. It only happens once per drive. The carbs have been fully rebuilt and tuned and pretty much all of the anciliaries have also been replaced over time. I'm completely baffled to the point that im not enjoying taking her out any more as i know its going to happen. It has new plugs, leads, dizzy, points, fuel filter and the timing is correct etc etc but did the same thing before all these were replaced too. I wonder if anyone has any ideas that i could try?

Thanks folks.... picture of said pain in the butt( ignore the croc clips i do have proper ones!) :)

received_10216557001538152.jpg

  • Like 1
Link to post
Share on other sites
  • Big Vern changed the title to End of my tether! 86 S3 N/A

Upgrade today to remove Google ads and support TLF.
  • Replies 65
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

So i went out for a spin today....maybe 40 mins of driving with no problems! Still early days but i think the ignition amplifier may have sorted it! Makes such a nice change and the sun was shini

Hi John, so far ive only been out once due to this crappy weather. It got up to temperature and didn't stumble. I'm not holding my breath just yet as being intermittent it hasn't always happened every

Hi folks, apologies for the delay in responding, i've been (to the best of my abilities!) fault finding all week to see if can make use of all these great suggestions to solve my problem. First of all

Posted Images

3 hours ago, Big Vern said:

 It has new plugs, leads, dizzy, points, fuel filter and the timing is correct etc etc but did the same thing before all these were replaced too. 

Does it have points or electronic ignition, also you've not mentioned the coil although it sounds more like a fuel problem than ignition?

Next time it happens, pull over & whip the tops off the carbs to check there's fuel in them. I'm thinking maybe contamination in the tanks or a fault with the pump disrupting the flow. 

PS Looks a nice job with the red cam covers & silver manifold :thumbup:

Cheers,

John W

http://jonwatkins.co.uk

Link to post
Share on other sites

The fact that it comes and then goes with consistency is remarkable but some wise old wag may have insight into how that occurs. I've had fuel lines from tanks in a Sunbeam Alpine clog up, stalling the car until sufficient time passed for the offending clag to slump away from the passages but your case description doesn't quite look to be the same.

Link to post
Share on other sites
10 hours ago, jonwat said:

Next time it happens, pull over & whip the tops off the carbs to check there's fuel in them. I'm thinking maybe contamination in the tanks or a fault with the pump disrupting the flow. 

Also remove the filler caps & listen for an inrush of air, they may be causing a vacuum in the tank  :thumbup:

Cheers,

John W

http://jonwatkins.co.uk

Link to post
Share on other sites

Jon, the coil, fuel pump, tanks and fuel lines have all been replaced, ive also replaced the fuel. The funny thing is, before i changed all these, it did exactly the same thing. Everything i try doesnt cure it. Its very strange. I will try taking the carb tops off as you suggest. I'll also check the inrush of air from the filler caps. I WILL find out what it is eventually if it kills me!!!

Thanks for your help guys any suggestions here are very helpful.

  • Like 1
Link to post
Share on other sites

The fact that it happened before you rebuilt everything and it still persists does suggest something else missed. I would however add that I had something similar with my N/A, took everything off, refurbished carbs, leads, plugs etc. but still rough running and stalled when idling after a while. It turned out that I'd dropped one of the new plugs when fitting and closed the gap but hadn't noticed. So I thought I still had the same problem, but I'd actual created another - unfortunately the plugs were the last thing I rechecked.

I'd be tempted to disconnect the fuel line from the carbs and connect an extension fuel pipe, turn on the ignition and empty the fuel into a large petrol container (checking the flow is strong and even), then filter it through a mesh into another container to see if there is any gunk pulled from the tank. I had one of my tanks block with what I can only describe as rubber glue like small marbles. Ended up draining the tanks, fortunately mine are alloys, and the bolt at the bottom was easy to work with through the access hole.

Check the plugs again for gaps but also their condition in case one carb is not getting enough or too much fuel through.

You suggest it only happens once after 15 mins, presumably it cools down or fuel reloads, either way after a further 5 mins it's fixed itself, but then after this it does not recur? 

I notice your manual choke connected to front carb (is that normal) and wonder if this is affecting running the engine when things get hot - perhaps slightly engaging the choke because of the cable routing. Try disconnecting the cable for one run out and see what happens? 

 

 

 

 

Link to post
Share on other sites
  • Gold FFM

It sounds related to engine temperature, a certain range reached after about 15 minutes of running where there is a problem with fuelling. I'm not that familiar with the 912 in the Esprit, is there any device for temperature compensation that could be acting up?

Filip

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to post
Share on other sites

That was my thought, something almost unrelated to anything else.  EG When the thermostat opens there is some interference in the temp guage wiring, voltage stabiliser circuit that causes interference somewhere in the ignition circuit - fairly improbable I know!

Link to post
Share on other sites
  • Gold FFM

Is it worth checking all earth straps etc. Not sure whether that could impact. I imagine they are pretty clean looking at your engine. Are they are all present as they should be? I am guessing rubbish in the tanks though / fueling... 

Link to post
Share on other sites

My WAG (Wild A** Guess):  Roll over valve? Easy to check/clean, not usually looked at.....🙄

Atwell Haines

'88 Esprit

Succasunna, NJ USA

Link to post
Share on other sites
On 24/03/2021 at 09:31, DaKa said:

It turned out that I'd dropped one of the new plugs when fitting and closed the gap but hadn't noticed. So I thought I still had the same problem, but I'd actual created another - unfortunately the plugs were the last thing I rechecked.

Damien, i've had maybe 3 sets of spark plugs now all gapped correctly and it still persists...
 

On 24/03/2021 at 09:31, DaKa said:

I'd be tempted to disconnect the fuel line from the carbs and connect an extension fuel pipe, turn on the ignition and empty the fuel into a large petrol container (checking the flow is strong and even), then filter it through a mesh into another container to see if there is any gunk pulled from the tank. I had one of my tanks block with what I can only describe as rubber glue like small marbles. Ended up draining the tanks, fortunately mine are alloys, and the bolt at the bottom was easy to work with through the access hole.

I will get my garage to try this Damien, I have alloy tanks from SJ's so this shouldn't be too difficult.
 

On 24/03/2021 at 09:31, DaKa said:

You suggest it only happens once after 15 mins, presumably it cools down or fuel reloads, either way after a further 5 mins it's fixed itself, but then after this it does not recur?

Yes it usually clears while i'm driving. I.e i dont have to stop, it just goes away after 5 mins or so and doesn't re-occur. It never happens at the beginning of a drive, only when ive been driving maybe 15 mins or so. Next time i'm going to time it to see if its exact!

On 24/03/2021 at 09:31, DaKa said:

I notice your manual choke connected to front carb (is that normal) and wonder if this is affecting running the engine when things get hot - perhaps slightly engaging the choke because of the cable routing. Try disconnecting the cable for one run out and see what happens? 

Now this is interesting, i've never noticed that before, and now having had a google search it appears it should be on the 'back' carb. I will swap it over anyway and in between take it for a drive. I'll also before i do that follow the cable back to see if it is touching anything......

 

On 24/03/2021 at 10:09, Escape said:

It sounds related to engine temperature, a certain range reached after about 15 minutes of running where there is a problem with fuelling. I'm not that familiar with the 912 in the Esprit, is there any device for temperature compensation that could be acting up?

 

 

23 hours ago, 910Esprit said:

That was my thought, something almost unrelated to anything else.  EG When the thermostat opens there is some interference in the temp guage wiring, voltage stabiliser circuit that causes interference somewhere in the ignition circuit - fairly improbable I know!

Right now i'll look at anything! I have the manual so i'll certainly check the wiring and also the earth straps too Henry

 

21 hours ago, CarBuff said:

My WAG (Wild A** Guess):  Roll over valve? Easy to check/clean, not usually looked at....

As far as i know, i think the Roll Over Valve was only fitted to to Federal Cars not UK ones. I may stand corrected on that.


Thanks guys for the suggestions, at least it gives me an element of hope that i may find out whats going on!

I shall report back :)

Link to post
Share on other sites

I have an 87 turbo HC, it has two wax thermostats in the coolant part of the inlet manifold that change the vacuum circuit as the engine reaches normal temperature, when driving you can tell when they operate. Not sure if an NA has these but if it does I would have a good look at the vacuum circuit. 

Link to post
Share on other sites
18 hours ago, Steven162 said:

I have an 87 turbo HC, it has two wax thermostats in the coolant part of the inlet manifold that change the vacuum circuit as the engine reaches normal temperature, when driving you can tell when they operate. Not sure if an NA has these but if it does I would have a good look at the vacuum circuit. 

Thanks Steve, im not sure if the N/A cars do as ive never heard of it, maybe someone could correct me if im wrong?

Link to post
Share on other sites

Certainly teh two were present in later Excels which were all NA so would assume the later Esprit has them also. Earlier I think just had one. If it is those, they simply switch on the vacuum to the dissy and carbs, so could be things like a break in the pipe that carries that vacuum meaning the switch from cold to moderate temperature is actually go straight cold running settings to hot running settings. Those pipes are known to perish, but be careful replacing them as they contain a restrictor part way (it's only a fuel jet that's been re-purposed) to keep the vacuum from being off-off-off-fullyon as the engine cycles through the 4 cylinder sequence.

Link to post
Share on other sites

Hi folks, so the weather being as it is over the last couple of days i thought i'd get out on the old girl and see if i could give an update.

Yesterday I started the car and after the usual time and temp (about a quarter way up on the gauge) it went lumpy so i took the tops of the carbs off and there was fuel coming through. I also checked there was no inrush of air going into the tanks which there wasnt.

So, next i checked the spark plugs. I had previously gapped them at 0.7mm on advice of my mechanic, so i changed them to 0.9 as per the manual and it took it for a spin. It was lumpy all the way so ive now changed it back again, and took it for a short drive round the block and it ran like it did before, which was fine although i didnt have enough time to get it up to temp or take it for a longer drive.

Today though i cleaned the earth on the chassis where the battery and starter motor are attached. I'm not sure if there are any others i need to clean? I also took all the jets out of the carb to clear the holes in case any were block which they werent as i ran some wire through all the holes. I also changed the choke cable to the back carb.

I looked in the manual for vacuum pipes to the distributor. I cant seem to find anything in relation to this or the wax thermostats in the inlet manifold? I'm pretty sure i dont have any although i am willing to stand corrected if someone els could confirm but also how to find it!

I need to take her out again now so will report back but the only thing i can really do next is check the quality of the fuel. Being a N/A car i know the fuel pressure is lower, could i for example take the feed to the carbs and put it in a large clean empty coffee jar, switch the ignition on and off to collect some fuel, or am i being stoopid as i dont want it to shoot everywhere? Forgive my knowledge. Im learning all the time with helpful advice from here but i'm no mechanic!

Cheers guys

 

 

IMG_3704.jpg

Link to post
Share on other sites
  • Gold FFM

Is there not also an earth from the carbs? or similar? Interesting the gapped sparks switch to normal made a difference - mine has never had gapped plugs and runs well. I reckon you have weak spark / something electrical? 

Link to post
Share on other sites
2 hours ago, Big Vern said:

Yesterday I started the car and after the usual time and temp (about a quarter way up on the gauge) it went lumpy so i took the tops of the carbs off and there was fuel coming through. I also checked there was no inrush of air going into the tanks which there wasnt.

You seem to have cuecked all of the suggestions made, so, can you give us a more detailed explanation of "lumpy", examples etc? Does it tick over ok & cruise ok, does it miss under load or pop on the overrun? Once it's over it's lumpy period does it run great until you switch off.

You've not mentioned the electronic ignition unit, assuming it has one, are you sure it's ok? Did you check the coil wasn't too hot to hold?

It's difficult to tell from the picture so are the carbs correctly mounted with regard to the gaps between them & the spacers & manifold?

Finally what about the float levels, are they correct for the engine spec & the carb jets as per the manual? Are they properly balanced & the idle mixtures correctly set?

I think that's all for now 😃

  • Like 1

Cheers,

John W

http://jonwatkins.co.uk

Link to post
Share on other sites

The NA should have two thermal valves. The Ignition Thermal Valve is fitted to the centre of the inlet manifold water rail and below a coolant temperature of 60OC it directs inlet manifold pressure to the distributor for full advance to aid cold idle and drive-ability. The Cold Enrichment Thermal Valve is fitted to the rear of the inlet manifold water rail and below a coolant temperature of 35OC it bleeds off the crankcase breather to enrich the fuelling. 

The Service Notes also show a Air Inlet Temperature Control System that directs warmer air from a shroud around the exhaust pipe into the airbox when the airbox temperature is below 20OC.

Any of these systems could cause running issues if they aren't working properly, especially by having an air leak.

  • Like 1
Link to post
Share on other sites
On 30/03/2021 at 15:26, jonwat said:

You seem to have cuecked all of the suggestions made, so, can you give us a more detailed explanation of "lumpy", examples etc? Does it tick over ok & cruise ok, does it miss under load or pop on the overrun? Once it's over it's lumpy period does it run great until you switch off.

You've not mentioned the electronic ignition unit, assuming it has one, are you sure it's ok? Did you check the coil wasn't too hot to hold?

It's difficult to tell from the picture so are the carbs correctly mounted with regard to the gaps between them & the spacers & manifold?

Finally what about the float levels, are they correct for the engine spec & the carb jets as per the manual? Are they properly balanced & the idle mixtures correctly set?

I think that's all for now 😃

Thanks John,

When i say lumpy, the only way i can describe it is it runs ok and then Kangaroo's down the road for 5 mins or so, if i slow down and stop, it doesnt quite stall but its close. It doesnt pop on the overrun. Once the kangarooing goes away it carries on as normal.

It does have electronic ignition and the coil was replaced maybe a year ago and does not get hot at all, in fact it doesnt even get warm. The warmest part in that little box is the ignition amplifier.

The carbs look to be mounted ok and the spacer gaps seem to be ok. Ive checked they are 1mm all round. Im not sure how to tell if there is an air leak if there is one.

and ive also checked the float levels and had them professionally balanced and tuned twice too...

 

 

On 30/03/2021 at 16:53, sailorbob said:

The NA should have two thermal valves. The Ignition Thermal Valve is fitted to the centre of the inlet manifold water rail and below a coolant temperature of 60OC it directs inlet manifold pressure to the distributor for full advance to aid cold idle and drive-ability. The Cold Enrichment Thermal Valve is fitted to the rear of the inlet manifold water rail and below a coolant temperature of 35OC it bleeds off the crankcase breather to enrich the fuelling. 

The Service Notes also show a Air Inlet Temperature Control System that directs warmer air from a shroud around the exhaust pipe into the airbox when the airbox temperature is below 20OC.

Any of these systems could cause running issues if they aren't working properly, especially by having an air leak.

Forgive me, i cannot for the life of me find any valves. I wonder if anyone has a pic so i can visually see where they are. Ive had a look in the manual and most of the diagrams are for the Turbo's....

Link to post
Share on other sites

Sorry Brett, I was looking in the wrong section of the Service Notes and the two thermal valves I described are for the '87 onwards engines.

Does your engine have a throttle jack and/or air pump with divertor valve?

 

Link to post
Share on other sites
5 hours ago, Big Vern said:

Thanks John,

When i say lumpy, the only way i can describe it is it runs ok and then Kangaroo's down the road for 5 mins or so, if i slow down and stop, it doesnt quite stall but its close. It doesnt pop on the overrun. Once the kangarooing goes away it carries on as normal.

It does have electronic ignition and the coil was replaced maybe a year ago and does not get hot at all, in fact it doesnt even get warm. The warmest part in that little box is the ignition amplifier.

The carbs look to be mounted ok and the spacer gaps seem to be ok. Ive checked they are 1mm all round. Im not sure how to tell if there is an air leak if there is one.

and ive also checked the float levels and had them professionally balanced and tuned twice too...

So, I can't think of anything that would cause those symptoms & then go away except a lack of fuel or air flowing into the carbs. What about the air intake, is it all clear & complete? I'm thinking of a problem Sparky had with a GT3, I know yours isn't  a turbo but it's worth checking. Failing that I'd suggest getting it on a rolling road where you can properly investigate while the problem is occurring. 🥺

Cheers,

John W

http://jonwatkins.co.uk

Link to post
Share on other sites

We are definitely most of the way through the bottom of the piece of wood that forms the bottom of the barrel., not just scraping it.

Wacky stuff, like something wrong with coolant thermostat and it's opening too soon/ late that it moves to changing coolant flow and engine needs more rich/lean mixture but then OK once it's fully hot. I'm doubting it but just trying to think of anything that changes via temperature.

Not saying I've ever heard of it, but there's not a lot of stuff on these early engines that's actively controlled by temperature.

Link to post
Share on other sites

Hi Brett. 

This maybe completely irrelevant but as you're struggling I thought I'd mention it. Is the voltmeter charge showing as low on the gauge when at the start of your journey? I say this because there is a second wire that should be attached to the alternator to 'excite it' into charging fully from the off. Mine had come off and the alternator wasn't charging enough until I revved beyond 3k revs or so and these extra revs then it kicked into action and it charged normally. I though it was temperature related as well but it was because I don't rev it hard from cold so it only solved itself when I revved higher after it had warmed up. Could this be some kind of low power problem (or surge)? Seems strange that your car runs worse with the correctly gapped plugs so could be related. Maybe it's lacking the juice to jump a spark .9mm across the plugs and it helps it at .7mm.

Cheers, Steve. 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...