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

[GordonMasson 128]

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

 

[jonwat 451]

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. ☺

[GordonMasson 128]

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?

[jonwat 451]

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. 😀

 

[GordonMasson 128]

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.

 

[Guest]

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/

[jonwat 451]

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. 

[GordonMasson 128]

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. 

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.

[jonwat 451]

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.

[Big Vern 108]

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

 

[GordonMasson 128]

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 ?

[GordonMasson 128]

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?

[ekwan 70]

No point guessing. But a fuel pressure gauge from Eurocarb and see what your fuel pressure is reading. It will either be too high or too low. 

If it's a Dellorto for an NA car, the fuel pressure should be no more than 2psi. Weber's run at slightly higher pressures. 

Don't waste time like me guessing. 

Edited November 24, 2019 by ekwan

[Choppa 215]

I believe that the top plate on the Dellorto has a small hole that vents to air. If fuel is being pushed past the needle valves when the ignition is on but the engine is not running, at some point the air space above the float chamber will fill up and fuel will leak through that small hole, into the trumpet, onto the air filter, and then past that and down onto the distributor. I've experience this exact problem which was cured by fitting a new set of vitron tipped needle valves. @Sparkywill probably remember seeing the problem first hand and helping to fit the replacement needle valves at the time.  If you are not seeing fuel being pushed past the needle valve as I describe I'd suggest Eurocarb did an OK job on that section of your carbs. 

It is also my firm belief that a significant proportion of the engine fires that have happened to owners over the years have  been caused by  failing float chamber needle valves  rather than failed fuel pipes.

Edited November 24, 2019 by Choppa

[Jeanvm 105]

The problem with the new fuel pump is that it give too much pressure. It is better to have a pressure regulator that can reduce the pressure at 2 à 3 psi. See the foto.

 

[Choppa 215]

This is what to look for!!

 

[ekwan 70]

You need the correct fuel pump. A PR is only useful if you have a means of bleeding excess fuel back to the fuel tank. 

 

Those look like Dellorto carburetors. 3psi is too much for them. 

Edited November 25, 2019 by ekwan

[GordonMasson 128]

Yep, that was pretty much what I was getting Choppa

 

@JeanVM - Think you are right. Although I don't understand why this would start happening all of a sudden when the carbs were rebuilt by Eurocarb, I think that having done it twice and there still being a slight leak there would be enough to suggest putting in a regulator for safety's sake. I think the  S1 may  even run lower than 2 psi?

Shame about the fact it will look non standard at shows but better having a car to show than a burnt out shell!

https://www.dellorto.co.uk/shop/car-accessories/fuel-pumps-regulators-accessories/pressure-regulators-and-parts/malpassi-petrol-king-pressure-regulator/

https://www.dellorto.co.uk/shop/car-accessories/fuel-pumps-regulators-accessories/pressure-gauges-carburettor/wfr150kit-webcon-fuel-pressure-gauge-0-15-psi-line-adaptor/

 

Shame about the gauge being 0 - 15 psi, 0 - 5 would have been better. I guess removing the gauge and replacing it with the blanking plug would be a good compromise.

Thanks for your input

 

[Jeanvm 105]

This gauge is a better option: https://www.dellorto.co.uk/shop/other-carburettor-injection-parts/fuel-injection-parts/injection-pressure-gauge/weber-fuel-pressure-gauge-1-8-bar/

And to have one is knowing what the fuel pump is doing.

[Jeanvm 105]

Sorry, wrong from me. this is bar not psi: so not a good one.

[drdoom 447]

On 24/11/2019 at 23:38, ekwan said:

You need the correct fuel pump. A PR is only useful if you have a means of bleeding excess fuel back to the fuel tank. 

 

 

Not true, deadhead FPR's are commonplace in carbureted engine applications and occasionally on EFI as well.

[ekwan 70]

5 hours ago, drdoom said:

Not true, deadhead FPR's are commonplace in carbureted engine applications and occasionally on EFI as well.

Yes. I found out subsequently for it's been years since I dealt with carbs.

 

[marcbria 18]

If its any comfort, I have stromberg carbs on my S1 with a relatively new pump and its always ticked every ~10 seconds once the carbs are full if its not running and it doesn't flood the carbs and otherwise seems happy. I just assumed that this was normal as long as no fuel was leaking anywhere.

Cheers,