free hit
counters
S1 carbs leaking - fuel pump clicking with ignition on and engine off - Fuel System/Carbs - The Lotus Forums Jump to content
GordonMasson

S1 carbs leaking - fuel pump clicking with ignition on and engine off

Recommended Posts

My car was running ‘lumpy’ and i was advised by Lotus Bits that the carbs couldn’t be balanced properly and needed to be rebuilt. 

I sent them to Eurocarb for a full rebuild and when they came back and put on the car, I had the usual click of the fuel pump as they filled up but rather that the clicking stopping, you would hear a click from the fuel pump every 5 seconds or so and a slight smell of fuel. 

i haven't run the car on the road for obvious reasons but at one point I did the same check and the fuel pump kept running and the carbs flooded.

I sent the carbs back too eurocarb and got them to replace the needle valves but I am still getting the same issue.

Nothing else has changed on the car bar the fuel hose. Same pump as on the car from new. 

‘If you put your ear to the top of the carb ... rear carb in particular, with the engine off and the ignition on you hear the clicks from the pump followed by a. sort of ‘snoring’ noise which I assume is fuel going past the needle valve and into the float chamber. 

Any ideas?

Thanks

Spoiler

Carbs leaking fuel pump

 

Share this post


Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.
3 hours ago, GordonMasson said:

Nothing else has changed on the car bar the fuel hose. Same pump as on the car from new. 

‘If you put your ear to the top of the carb ... rear carb in particular, with the engine off and the ignition on you hear the clicks from the pump followed by a. sort of ‘snoring’ noise which I assume is fuel going past the needle valve and into the float chamber. 

Any ideas?

Thanks

  Reveal hidden contents

Carbs leaking fuel pump

 

As the pump is now over 40 years old it could be the pump diaphragm has a hole or tear in it causing the pump to loose pressure. ☺


Cheers,

John W

http://jonwatkins.co.uk

Share this post


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

As the pump is now over 40 years old it could be the pump diaphragm has a hole or tear in it causing the pump to loose pressure. ☺

It’s really the other way round I think. I assume the pump is over pressuring the system hence the fuel leak at the carbs.

if it was a leak in the diaphragm I would have thought that would lead to fuel starvation?

Share this post


Link to post
Share on other sites
19 minutes ago, GordonMasson said:

It’s really the other way round I think. I assume the pump is over pressuring the system hence the fuel leak at the carbs.

if it was a leak in the diaphragm I would have thought that would lead to fuel starvation?

Depends on the size of the hole in the diaphragm, I'd be looking to replace a 40 year old pump anyway, it's a breakdown waiting to happen.

If it's going into the carbs while the engine is stationary then where's it going once the float chambers are full?

It's easy to test the float valves, remove the float chamber tops, hold the floats up to close the valves & turn on the igniton to see if they leak. 😀

 


Cheers,

John W

http://jonwatkins.co.uk

Share this post


Link to post
Share on other sites

May be right about the pump.

Eurocarb have had the carbs twice, doing a full overhaul the first time and because of the problems, replacing the needle valves and checking everything else again the second time.

I would hope that Eurocarb are way more able to set the carbs up than I am so I am not keen on pending them up again.

 

Share this post


Link to post
Share on other sites

You could plum a PSI gauge in the line from the pump to the carb and get a true reading on the fuel pressure.  Low pressure electric fuel pumps are cheap but I would install a pressure regulator just to be certain the pump doesn’t over pressurize the carbs.

https://www.dellorto.co.uk/product-category/car-accessories/fuel-pumps-regulators-accessories/pressure-regulators-and-parts/


Cheers, Gavin

Share this post


Link to post
Share on other sites
On 26/10/2019 at 20:19, GordonMasson said:

I would hope that Eurocarb are way more able to set the carbs up than I am so I am not keen on pending them up again.

Not sure what "pending" is but you meant opening then it's only 4 screws per carb & lifting off the float chamber covers, use some elastic to hold the floats up & the valves closed while you turn the ignition on. :thumbup:


Cheers,

John W

http://jonwatkins.co.uk

Share this post


Link to post
Share on other sites
46 minutes ago, jonwat said:

Not sure what "pending" is but you meant opening then it's only 4 screws per carb & lifting off the float chamber covers, use some elastic to hold the floats up & the valves closed while you turn the ignition on. :thumbup:

Typo - Pending = opening.

Yep, understand its an "easy" job but the point I am making is that if Eurocarb have rebuilt the carbs and then had them back a second time when they were leaking, replaced the needle valves for a second new set and rechecked all the settings and levels, do you really think that having never been inside a Dellorto before,  I would do a better job than Eurocarb. I would certainly hope not since that's why I paid for a carb specialist to do them in the first place.

Share this post


Link to post
Share on other sites
On 26/10/2019 at 08:39, GordonMasson said:

‘If you put your ear to the top of the carb ... rear carb in particular, with the engine off and the ignition on you hear the clicks from the pump followed by a. sort of ‘snoring’ noise which I assume is fuel going past the needle valve and into the float chamber. 

  Reveal hidden contents

Carbs leaking fuel pump

 

OK, so you think the new needle valve(s) are leaking but you don't know where the leaking fuel is going & don't want to take the float chamber tops off to test them & disagree that your 40 year old pump could have a leaking diaphragm. 

I can't remember how often the pump ticks to maintain pressure on a stationary engine but think it was less than every 5 seconds on an idling engine.

I think that's me done.

Good luck finding a solution.


Cheers,

John W

http://jonwatkins.co.uk

Share this post


Link to post
Share on other sites

My pump clicks every 5 seconds or so all the time, i just presumed it was normal?

 

Share this post


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

OK, so you think the new needle valve(s) are leaking but you don't know where the leaking fuel is going & don't want to take the float chamber tops off to test them & disagree that your 40 year old pump could have a leaking diaphragm. 

I can't remember how often the pump ticks to maintain pressure on a stationary engine but think it was less than every 5 seconds on an idling engine.

I think that's me done.

Good luck finding a solution.

I agree that the needle valves must be passing fuel that's not required but my point was that if they have been replaced twice and set up by Eurocarb twice then I doubt I could set them up better.

I agree, it could be that the fuel pump is over pressurizing the system but I would have thought that if the diaphragm was leaking that would lead to fuel starvation rather than the other way around....but I did take your point in my response on Saturday "Could be right about the fuel pump".

Thanks for your input.

On ‎28‎/‎10‎/‎2019 at 01:16, gtookey said:

You could plum a PSI gauge in the line from the pump to the carb and get a true reading on the fuel pressure.  Low pressure electric fuel pumps are cheap but I would install a pressure regulator just to be certain the pump doesn’t over pressurize the carbs.

https://www.dellorto.co.uk/product-category/car-accessories/fuel-pumps-regulators-accessories/pressure-regulators-and-parts/

Will look into a pressure regulator...... I think its about 4psi for an S1 ?

Share this post


Link to post
Share on other sites
11 minutes ago, Big Vern said:

My pump clicks every 5 seconds or so all the time, i just presumed it was normal?

 

To be honest, I don't remember hearing my pump click at all with the engine off, ignition on and after the carbs were filled but it may be different on an S1 compared to later cars?

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.


×
×
  • Create New...