Possible carb problem? Possibly not…

[miked]

Agree, and the point I tried to make that a screw can be responsible for the butterfly not seating by binding on the edge of the screw hole. Needle file fettle to the screw hole offending area. I would not touch tne edges either.

[Verve]

You may have more than one issue at play here ... a vacuum leak in the piping to the servo , or to the headlamp cross member right up to the dash vacuum switch (when non-failsafe headlamps down ) , will give easy excess air direct to number 1 ( causing it to to be too lean at "idle" & not run properly ) , whilst also showing a lower air flow through the more difficult ( butterflies virtually closed ) carb` at idle ... you have those symptoms (including backfire on lift off ... unburnt fuel from no 1 ) .

Once off idle , the open butterflies give an easier air flow so the problem is less apparent ... & you can just simply block off the vacuum take offs temporarily , to test & eliminate that possible demon ...

Good Luck !

Paul .

[pabbage]

You may have more than one issue at play here ... a vacuum leak in the piping to the servo , or to the headlamp cross member right up to the dash vacuum switch (when non-failsafe headlamps down ) , will give easy excess air direct to number 1 ( causing it to to be too lean at "idle" & not run properly ) , whilst also showing a lower air flow through the more difficult ( butterflies virtually closed ) carb` at idle ... you have those symptoms (including backfire on lift off ... unburnt fuel from no 1 ) .

Once off idle , the open butterflies give an easier air flow so the problem is less apparent ... & you can just simply block off the vacuum take offs temporarily , to test & eliminate that possible demon ...

Good Luck !

Paul .

Hi Paul - thanks for the message. I noticed you are based in Retford; strangely the car is currently with my Dad (he has a garage) just outside of Retford. If you want to come over and breathe some magic on the car feel free!

I'm visiting him this week and so I'll try isolating the vacuum to the headlights and brakes… before attacking the carbs. I take it its just a case of blanking off that feed. This may well be a simple test. My Dad has been fiddling and confirmed that both one way valves appeared to be working 'one way' only.

Thanks again, Paul

[alaric]

Hi.

On my carbs one of the butterfly valve plates did not fit into the bore. All the others did. It is oversized despite the number being the same as the others. I measured it with vernier callipers to confirm. It may be that the sticking on fully closed doesn't actually matter if we consider the flow rates etc, but if I can remove a variable that might affect in carb barrel balance I will, which is why that plate is now history. Of course I am banking on the new plate being similar tolerance to the others...

Regards.

Sean.

[Verve]

You may have more than one issue at play here ... a vacuum leak in the piping to the servo , or to the headlamp cross member right up to the dash vacuum switch (when non-failsafe headlamps down ) , will give easy excess air direct to number 1 ( causing it to to be too lean at "idle" & not run properly ) , whilst also showing a lower air flow through the more difficult ( butterflies virtually closed ) carb` at idle ... you have those symptoms (including backfire on lift off ... unburnt fuel from no 1 ) .

Once off idle , the open butterflies give an easier air flow so the problem is less apparent ... & you can just simply block off the vacuum take offs temporarily , to test & eliminate that possible demon ...

Good Luck !

Paul .

Hi Paul - thanks for the message. I noticed you are based in Retford; strangely the car is currently with my Dad (he has a garage) just outside of Retford. If you want to come over and breathe some magic on the car feel free!

I'm visiting him this week and so I'll try isolating the vacuum to the headlights and brakes… before attacking the carbs. I take it its just a case of blanking off that feed. This may well be a simple test. My Dad has been fiddling and confirmed that both one way valves appeared to be working 'one way' only.

Thanks again, Paul

Hi ... only just seen your response ... yeh , send me a pm if you are still in the area & I`ll pop round & have a look ... I also have a Sprint on Dellortos !

It`s good your one way valves are working ... even though that won`t stop any potential leaks spoiling the party ... & yes , just block the take offs with a short blanked off hose .

Cheers ,

Paul .

[pabbage]

Update - I’ve blanked off the vacuum system but this didn’t make any difference. The airflow on cylinder one is half that of two (on the same carb) and the other cylinders. I can still remove ht lead 1 with no change to engine note.

Following that I removed the carbs - noted the following. Fuel chamber was a little grotty / I cleaned this out and checked jets. They appeared clear to light. Butterfly’s appeared to close ok. Remounted carbs - engine started with no issue but still noticeable lower air flow through 1 and no change in engine note if you remove ht lead.

At a a loss. Having previously changed plugs and leads Where do I go now?

Any help appreciated.

Paul

[mbell]

I think you need to identify if its carb or engine issue.Are you able to swap the carbs around and see if the issue stays or moves cylinder?

Maybe a compression test with carbs removed or do a leak down test.

[pabbage]

I think swapping the carbs sounds like a good step forward. Compression test was good. Thing is the car really does go well and certainly doesn’t feels like it’s running on three cylinders. At least to me ..

[alaric]

Hi. Just a few thoughts: Have you used new o rings and thackeries when re-mounting the carbs? When you had them off, did you hold the barrels up to a light and check that all butterflies had about the same light through them? Also, are you sure all the butterflies have the same number stamped on them and have the cutout near the progression holes?

Regards.

Sean.

[Verve]

Hi ... if your Elan is still local to me & you want some "moral support" , just let me know !

Cheers ,

Paul .

[SENC]

A leakdown test may provide insight or eliminate some possibilities. I chased a similar problem a while back on my Seven, and the leakdown test led to determination of a weak valve spring on the cylinder that wasn't pulling the same vacuum.

[pabbage]

Hi ... if your Elan is still local to me & you want some "moral support" , just let me know !

Cheers ,

Paul .

Thanks for for that Paul - I’ll put you on standby. I’ve taken them off and swapped back for front. Also replaced some part that looked suspect. Hoping to get them back on at the weekend and see if I have made any difference!

You may get a message! We’re down to goodwood in a couple of weeks so hopeful it’s running well.

[pabbage]

A leakdown test may provide insight or eliminate some possibilities. I chased a similar problem a while back on my Seven, and the leakdown test led to determination of a weak valve spring on the cylinder that wasn't pulling the same vacuum.

Thumbs up for a leak down test - it sounds like a good option as all else has failed so far.

[pabbage]

A little update - carbs came off and I cleaned them up - jets all came out and were cleaned. A throttle shaft and butterfly replaced (as there was a small slither of light on closure). New idle mix screws and springs were thrown at it. 1st carb was swapped for the 2nd carb and then all put back onto the car… and… problem solved!!

All four cylinders now appear to draw the same vacuum and all ht leads (when removed) cause the engine to stumble. So i'd almost say the problem is fixed … not sure what the actual problem was or if it was a mixture of many things but much improved.

I am struggling a little to get the carbs tuned but that more than likely my expertise and needing a little more time to play with them.

At this rate I may make it to goodwood!