16 replies to this topic

[SuperDeLuxeNick]

Hello all. Having some issues getting my mk1 running right. Is a 850cc with twin HS2 carbs, it starts and idles all okay. Not long had the car, a facet pump was already fitted, the twin hs2s I have added as it came with a knackered single.

Okay so issue one is that 90% of the time, float no. 1 overflows. I have replaced needle and gaskets and even adjusted the needle valve to lower the level. This seems to have sorted this but then the fuel finds another way out in passing by the new fuel line and hose clip on the float lid.

All the time I thought the other float was all good. However I have now also noticed a slight drip from that side too. Not sure exactly where from, the float seems dry but seems to be coming out near the jet.

This leads be to believe that perhaps the issues are related, I have found the facet pump listed as pumping 3-4.5PSI, is this too high for my carbs? Also, it always pumps. Like, ignition on and it pumps, fills the floats etc and just keeps pumping, whether it’s running or not, if the ignition is on then it’s pumping, shouldn’t it slow / stop once the pressure is built? I also have another mk1 with factory pump and this is what occurs on that one, I’ve never used a facet before...

Any help would be greatly appreciated! Thank you

[Cooperman]

The Facet pump needs a pressure regulator. Standard pressure is too high for twin SU's.

Fit a regulator and set it to around 2 psi and go from there. 

A Facet will always 'tick' when it is switched on and that is nothing to worry about. 

[nicklouse]

As above. But the new Vitron tipped float needles are meant to be good for a higher pressure.

 

 

also are the hoses new? Old ones can be very poor after a few years. And you are using correct fuel clips not jubilee clips screwed down tight that can pinch and cause leaks.

[SuperDeLuxeNick]

Thanks guys! Cooperman, do I need to to go filter king in the engine bay or can I get something smaller in the boot?

Yep the hoses are new, quality lines and proper clips used.

The fuel passes the gasket on one carb, or the line in. And seems to be coming out the carb body or jet on the other. After looking at regulators on minispares it does say that must be used with any facet pump so makes sense! Hopefully that sorts the problem

[Spider]

4 - 5 psi is on the high side for SU's, as Cooperman mentioned. 2.5 to 3.5 psi is ideal.

 

Just before you buy a regulator, I'd suggest checking the price of one of these vs a new Hardi Pump, Mini Spares have these, they are a German copy of the SU and run near silent like the genuine SU Pump.

[Cooperman]

I run a Universal Pressure Regulator in the engine bay. They cost round £20 on the web. I don't think Mini Spares sell them - well, they are not listed.

[whistler]

I use these pumps and mount in original position with an inline paper filter. https://simonbbc.com...r-installation/

[SuperDeLuxeNick]

Okay so actually got a regulator but thought I’d try an original pump that I know works well on our 67 countryman. Very frustrated to see that the right hand float still overflows from the overflow breather hole? And the jet on the left hand carb is wet... really not sure why! The carbs are newly serviced and all gaskets and pipe work is new

[Spider]

Noted that you've fitted new Needle & Seats, but are they genuine SU or aftermarket types ?  The SU types are Viton tipped.

Also, check the floats that they are not holding fuel, though, they may need replacing anyway as some of the older types are heavier than they should be.

[SuperDeLuxeNick]

Thanks Spider. Yep genuine kits as i live right by Burlen Fuels :)

 

Didn't renew the floats, perhaps i will try that next step. Its very frustrating to see the breather trickling out after the pump as filled up

[SuperDeLuxeNick]

Decided it must be floats so removed them and got a glass jar the same size as float chamber and filled with water, put a pipe on the float so i could blow in and simulate fuel.

 

Both floats rise when in the water and close off, however, one i could blow into and with medium effort i could push the float down with breath - the other i could blow as hard as i wanted and it stayed up! Doesn't appear to be any hole or anything but am pleased to have found fault. I put them back on the carbs (after cleaning again and making sure they operate) but the other way round, left on right and vice versa, and no leak! I feel the much lower fuel pressure (now fitted a regulator) and perhaps a final clean has done the trick. For peace of mind i think i will still replace the float that did have the issues originally though.

[Spider]

Some of the older floats are just heavy to start with, thicker or denser plastic, I'm not sure, but they can be a cause of the issues you've found. It might settle down with a swap as you've done, but I'd suspect it'll come back somewhere down the track. At least you'll know where to look !

[SuperDeLuxeNick]

We are back!

 

Still having woes with the twin HS2s.

 

I have started to set them up, centred the jets and set base settings, the pistons drop nicely with a click and it fired up and ran very well with an even exhaust note. Great.

 

Left it to idle and it then cut out and wouldn't start again. Checked the floats and they were dry so then removed the float lids fully and checked fuel was being pumped through after increasing the fuel pressure regulator a couple of turns, the floats now fill up nicely and don't leak. However it still won't fire and i find the following;

 

With the fuel pump active, if lift the right hand carb piston, nothing to note, no fuel or air moving. If i do the same to the left hand piston, fuel is being blown up the jet and flooding the carb body. Which one is correct?! I have a good understanding but limited here i am afraid. 

 

I have turned the pressure back down until it stops blowing through but am concerned it is now back to not being high enough to fill the floats!

 

And also how come one blows through and the other is dry?

 

Any help is appreciated as always!

 

Thank you :) 

[nicklouse]

Sounds like the carbs need a strip down and a full service by someone that knows the carbs. Have you compared the drop times for both. That will give you an idea of the quality of any previous rebuild.

 

have the carbs actually been matched?

[SuperDeLuxeNick]

They have both been serviced fully and the drop on each piston is very equal and uniform. I am booking it in for rolling road setup but wanted to be able to give it to the chap in a good state and feel as though i have solved a good few issues and operation is good but this fuel pressure issue is annoying, especially as they were running very nicely!