free hit
counters
Carburettor Jet Cleaning - Fuel System/Carbs - The Lotus Forums Jump to content
Sign in to follow this  
simonf

Carburettor Jet Cleaning

Recommended Posts

Hi Guys,

I believe my Jets are blocked on the carburettor closest to the boot and i wondered if i can get to them just by taking the cover off the delorto's. Has anybody else done this and is there any procedure to doing so? I was just going to lift the jets out blow them through, then stick a bit of fuel line hose into where the jet had come from and blow that through too! I have never had to perform this task before and want to make sure that i am doing it properly!

Will i have to set the carbs up again if i do this?

Your help as ever is greatlyappreciated!!

Best wishes

Simonf

Edited by simonf

REHABS FOR QUITTERS!!

Share this post


Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.

Yep just remove small cover on top which gives access to main and idle jets. blow through jets as you suggest.

You would not affect the existing mixture or balance by doing this operation

What are your syptoms?

cheers Steve

Share this post


Link to post
Share on other sites

The jets are acessible through the cover on top of each carb..remove the covers (4 screws, iirc) and then you can unscrew the jets..one at a time is best, so you don't get muddled. I had problems with midrange misfiring after last winter's engine rebuild.... If the car hasn't been used, modern fuels seem to be very prone to depositing varnish type deposits on the bore of the jets..with obvious results. Blowing through will not clear this sort of deposit. You may be able to find some solvent which will do the job,but I tried acetone, cellulose thinners and white spirit and got nowhere. The bore of the slow running jet is very much towards the lower end of what is advised by Dell'Orto for a 2.2 litre engine...so any reduction of hole size will result in problems. At this point,purists should stop reading.....I wanted to see if the bores were the correct size, so I sought a suitably sized bore gauge to see if it would enter the bore...ended up with a length of guitar string, which measured the correct diameter on both my micrometer and the digital vernier caliper...sure enough, it wouldn't fit through the jets, so I spent a happy evening in front of the telly gently reaming the jets out with the piece of guitar string...after all, I could always solder them up and bore them again. The end result was that all the midrange misfiring and hesitation disappeared; all the adjustment of carburettion, ignition etc. had not cured this problem, which had been driving me nuts. The engine now pulls cleanly through the rev range, like a train. I think I used an Ernie Ball custom gauge 17 string...you'll need to look up the jet nominal bore and find something the right size, and be Very Gentle, no frenzied hacking at it!! As far as setting up the carbs is concerned, they were probably set when the bores were correct so you might find they're OK..but it's always a good thing to set them up every so often in any event. Worth buying a 4 column vacuum gauge and having fun balancing everything...!!


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

Share this post


Link to post
Share on other sites

We are planning to attempt the easy method first.

The symptoms are ...

Very lumpy idle

Little to no difference to idle when plug leads are pulled from either cylinder fed by carb near flywheel.

Poor running at speed

Good spark at all plugs.

Good compression (As Far As I Remember) at all cylinders.

Engine was pressure washed with carbs attached.

Engine was run with only 5l fuel in the tanks after tanks had been drained and painted (see thread about fire brigade from Simonf).

Found no in-line fuel filter in the carb inlet where it should be (after we found the issues).

Choke has limited positive effect when first run.

Plugs free of soot, but not run long enough to see if it is truly lean.

Thoughts are.

Blocked jet

Blocked float valve

Water in carb (would stay there even after running as it wouldn't vaporise like petrol).

So plan A is.

Remove the plenum cover, start he car and cover the carb air inlet. If it's water in the float bowl it should be pulled through due to the vacuum effect of the engine cycle. If it's a partially blocked jet it may be moved out in the same way. If it's a blocked float valve it may increase the force on the valve and make it break free.

However, if this doesn't work, it's time to start checking the carb and ensuring all jets are clear, checking fuel float height etc.

Andy

Share this post


Link to post
Share on other sites

Andy/Simon

Fettling a fuel tank, no inline filter, fault apparent on both main and idle circuits - I'm liking the blocked needle/float valve theory....

cheers Steve

Share this post


Link to post
Share on other sites

Hi guys, thanks for the input.

I removed the plenum cover as AndyC suggested and covered the trumpets with my hand- although there was a point when the revs increased to propper idle speed and it did run smooth for a few seconds, the result was a little disapointing. However i did take her out for a run and noticed that the car wouldn't rev over 5500rpm unless you took your foot off the throttle slightly1 Then you could get it round to the redline. That got me thinking that maybe it was electrical! So when i got back to the garage i turned off all of the lights in the garage and i could see fireworks for the distributer cap! At first i thought it was coming for the electronic ignition feed coupling, but later remembered that andy and i mullered the coil lead and although we thought we had repaired it, it wasn't well enough. Anyway changed the coil lead for a cheep one and the revving is much better although the idle remains a little lumpy! Not sure yet if i can rev under load as i ran out of time! I will take her out for a run tonight and see whats what!

Thanks again for your input!

SiF


REHABS FOR QUITTERS!!

Share this post


Link to post
Share on other sites

If the carbs are out of balance then that would produce the symptoms you describe as at idle you'd only be running on the first carb.

I'd check the balance first if I were you.

Cheers,

John W


Cheers,

John W

http://jonwatkins.co.uk

Share this post


Link to post
Share on other sites

If thats how much you charge for the carb balancing thing (i believe thats its correct technical title) how much are you going to charge me for the six months hire of the big red metal craney thingy-me-bob!

Anyway on a serious note - any ideas on how the carbs would have become out of sync? I haven't fiddled with any of the mixture screws!


REHABS FOR QUITTERS!!

Share this post


Link to post
Share on other sites

Well I think they could go out with vibration, knocks and bumps...dropping you engine!!! lol only joking but taking you engine out might have disturbed them a bit. I know my mate who has a RS2000 joked about the del autos becoming untuned. I dont know how common it is but on my old twin SUs I had on the little MG I used to check them overy couple of months. Somtimes they would be fine sometimes they were out. Worth checking all the jets and even the seals. If you want I have 110 psi air on at work give them a sqirt to make sure there nothing hiding in the end. By the way your method of putting the HT leads on in the right order by going by the length was right....I hope? lol. Your earth strap did get conected back up didnt it? With out you may get a spark from an earth somewhere but not as big as if that strap is on. I know we joked about forgeting to put it on but I wasnt there by that point!!! Other thing I would try just start her up in ther dark turn off the light and make sure you not losing any spark from an earth some where? I know my things may sound a bit randon but as an unskilled car worked I would say they are worth checking.


 

"Belief is the enemy of knowing" - Crrow777

Share this post


Link to post
Share on other sites

There's no way you can remove & replace the engine & expect it to run smoothly without rebalancing the carbs.

Also, you stated "Little to no difference to idle when plug leads are pulled from either cylinder fed by carb near flywheel."

I wouldn't expect both idle jets in number one carb to get blocked at the same time, but if they were, when driving you'd notice a definate performance increase when she moved from the idle to the main jet circuit.

Balance the carbs before you start dismanteling them, it only takes a few minutes & will eliminate or prove my theory.

Cheers,

John W


Cheers,

John W

http://jonwatkins.co.uk

Share this post


Link to post
Share on other sites

Cheers john that sounds like a plan!

So How do i balance the carbs then? Is it just on the mixture? or is it more complicated than that?

Buddsy can i borrow your balancer thingy?

Andy - will you come and do it for me? LOL


REHABS FOR QUITTERS!!

Share this post


Link to post
Share on other sites

Just a quick up date, i haven't had the courage to strip the carbs down yet, but i did find that one of the HT leads was not attached properly! That has improved the situation but not cured it. The car now revs round to 6000rpm where it feels like it has hit the limiter and i am still not getting any more than 0.5lb boost(bit less actually), the idle is at a higher speed (900rpm) but it is still very lumpy, the car is hesitant under acceleration and slightly lurches if you hold the revs constant whether that is at low speed in 1st or 2nd or at higher speed in 4th of 5th. The symptoms are very marginally improved when the car is hot!

I will get brave this weekend and take the jets out, promise!


REHABS FOR QUITTERS!!

Share this post


Link to post
Share on other sites

Simon I got a book on del auto carbs here and the balancer, I prob wont have time to give you a hand but will drop them off to you 2 morrow if you want?


 

"Belief is the enemy of knowing" - Crrow777

Share this post


Link to post
Share on other sites

Guys,

My first post on here as I have only recently get my Esprit. I seem to have exactly the same fault with my car. It had been in for a C service with Moorland Jones last week and running well until last night when I returned from a run out (60 miles or so) and on the way back along the M40 it seemed a little hesitant circa 4000rpm. I then went to the Ace Cafe where it was running fine at the traffic lights 100 yards before parking and left for an hour. When I started up it was down on idle rpm and i thought it was just a little cold. The drive home showed a misfire/hesitation out of roundabouts/corners etc but put your foot down and seemed ok. Once home it seemed to run on 3 cylinders. Taken it in to MJ once again and yet to hear what they think but ill let you know what they find.

Have you sorted yours yet?

Trevor.


I'll get around to it at some point.

Share this post


Link to post
Share on other sites

We think we've found it, and despite the triggers (disturbing tanks, low fuel, no in-line filter etc,) it seems to have been electrical.

We managed a few seconds of what seemed good running once we found the right timing setting, then the wire in the dissy failed (looks like it was already 99% broken through and it couldn't handle the wire being moved as part of the adjustment).

Waiting to find out if Simon had it repaired to day..... of so he may have fitted the dissy again, and we'll then know more.

Andy

Share this post


Link to post
Share on other sites

An update on my own car. Syptoms, running apparently on 3 cylinders at idle, not revving beyond 5700 without the rev limiter seemingly cutting in and at cruise circa 80mph on the motorway, the car hunts slightly. Moorland Jones found the rear carb was flooding so fitted a new needle valve and no doubt blew out the jets, reset the float eight and now is running very well and revs through to 6500 no problem. Also the smell of petrol seems to have gone.

Trevor.


I'll get around to it at some point.

Share this post


Link to post
Share on other sites

Hi, interesting reading this thread, I've got very similar symptoms, on idle the rear two cylinders are not firing.  off idle they are fine. 

I've replaced the leads with new ones, checked the timing is good, and checked the idle jets are clear.  carb balance is good. 

What did it turn out to be causing cylinders 3 and 4 not to fire for you?

cheers,

simon

Share this post


Link to post
Share on other sites

Yes please sounds like the same problem I had but I am unsure what the cure was as I did a lot of other work on the car at the same time which solved my issue.

Share this post


Link to post
Share on other sites

Had a friend with an excel that had partially gummed up idle jets, ran fine on idle on choke when cold but stalled when the choke was in. He resorted to poking some thin wire down them to clear them out, probably not the best way but has worked fine since.

Took a while to find as on removal could blow them ok so had assumed they were clear.

Edited by Wilf

Share this post


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.

Sign in to follow this  

×
×
  • Create New...