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Author Topic: Twin 1 1/4 Su's again!!  (Read 262 times)

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jimivo

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Twin 1 1/4 Su's again!!
« on: September 25, 2018, 05:43:07 PM »
G'Day peeps, so I have been thinking about doing the SMOG run on international moke day. I thought I'd better give the beast a run on the F3 to see how it goes doing a 100k or so, haven't done much over 80k or so since fitting the carbs. All went well for a few clicks at 110k (aside from the usual flapping noises etc) but then suddenly started to stutter and felt like it was going to stop period. Dropped the speed back to 80 and it picked up again, as soon as I tried to give it some herbs it started coughing again. got off the freeway drove home OK including some 80 k sections. Would I be right in thinking fuel starvation? Have an SU AUF214EN pump, fitted been on for 3 years or so. I know the twins would probably use a bit more fuel than the 1 1/2 I took off. The  SU AUF214 is 12 volt negative earth, rear mounted, 7 GPH. According to Midel website Popular applications: Austin Healey Sprite MK2,3,3A, Austin 1800 Early, Morris Mini Minor, Morris Cooper'S', Morris 1100, MG Midget. Looking at maybe replacing with a Facet Silver Top Fuel Pump 6.5-8.0 psi 32gph.

http://www.sumidel.com/shop/item/facet-fuel-pump-65-80-psi-32gph.

Anyone fitted one of these? Thoughts? Cheers, Jim.

Terry

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Re: Twin 1 1/4 Su's again!!
« Reply #1 on: September 25, 2018, 07:09:28 PM »
Hi,

the carby is only designed to handle 1-3psi so pumping 6-8psi of fuel in I doubt it would even start as there would be that much in there.

The fuel pump should be fine s just disconnect the hose from the carby and turn the pump on and if it comes out in a steady or pulsing flow  and not a dribble then it should be okay. If it is a dribble check for a blocked filter or maybe something in the tank if you have a large filler where you can put your hand down and feel around.

Otherwise look at the carby and see if there is a problem with the mixture or if  only one carby is getting fuel and maybe go for a drive again and when it starts to 'starve' pull the choke cable out and see if that improves things. The choke will move the jet tube down and allow more fuel past the needle.

Also watch your temperature gauge to see if the temp goes up when it starts to starve.

Terry
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is.


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bellbrae

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Re: Twin 1 1/4 Su's again!!
« Reply #2 on: September 25, 2018, 07:21:21 PM »
Hi
I had this problem with twin 1&1/2 carbies when the pressure in the fuel tank equals the suction of the carbies it starves the carbies .
Undo the fuel cap and go for a drive if it doesn't starve then you may have a blockage in the return line to the petrol tank. This is a quick way to check.
Good luck with it.
Drew.
Drewy

Terry

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Re: Twin 1 1/4 Su's again!!
« Reply #3 on: September 25, 2018, 07:34:42 PM »
Hi
I had this problem with twin 1&1/2 carbies when the pressure in the fuel tank equals the suction of the carbies it starves the carbies .
Undo the fuel cap and go for a drive if it doesn't starve then you may have a blockage in the return line to the petrol tank. This is a quick way to check.
Good luck with it.
Drew.

I agree with that as I have had that problem too where the breather on the cap had been blocked up.

Terry
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is.


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Pete Power

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Re: Twin 1 1/4 Su's again!!
« Reply #4 on: September 26, 2018, 02:17:04 PM »
Tonight when I'm out for a run and run out of Puff I'll take my hat off.
Happy Mokin
Regards
Pete

1981 Californian 1275 Galv "Mighty Moke"

"Just because you're breathing doesn't mean you're alive!"

jimivo

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Re: Twin 1 1/4 Su's again!!
« Reply #5 on: September 26, 2018, 03:59:15 PM »
Hi
I had this problem with twin 1&1/2 carbies when the pressure in the fuel tank equals the suction of the carbies it starves the carbies .
Undo the fuel cap and go for a drive if it doesn't starve then you may have a blockage in the return line to the petrol tank. This is a quick way to check.
Good luck with it.
Drew.
It's been raining pretty heavily so not game to get on freeway yet, I know the 1 1/2 su I took off had a return , but there isn't one on the twin su's? There was also a hose from the fuel tank to the Charcoal canister ( since removed ) which is now just venting to atmopshere have blown back through it, seems clear. I will give the fuel cap off a try when the weather clears. Cheers Jim


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Re: Twin 1 1/4 Su's again!!
« Reply #6 on: September 26, 2018, 04:55:21 PM »
Hope you get it sorted Jimivo it would be great if you could join us for IMD.
We have only seen you driving in the opposite direction on the other side of the road :)


Alan S  8) 
I've told you a million times stop exaggerating!

Terry

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Re: Twin 1 1/4 Su's again!!
« Reply #7 on: September 26, 2018, 05:07:26 PM »
Hope you get it sorted Jimivo it would be great if you could join us for IMD.
We have only seen you driving in the opposite direction on the other side of the road :)

Alan S  8)

So does that mean he is travelling in the same direction as you? :)

Terry
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is.


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jimivo

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Re: Twin 1 1/4 Su's again!!
« Reply #8 on: September 26, 2018, 05:13:20 PM »
Hi,

the carby is only designed to handle 1-3psi so pumping 6-8psi of fuel in I doubt it would even start as there would be that much in there.

The fuel pump should be fine s just disconnect the hose from the carby and turn the pump on and if it comes out in a steady or pulsing flow  and not a dribble then it should be okay. If it is a dribble check for a blocked filter or maybe something in the tank if you have a large filler where you can put your hand down and feel around.

Otherwise look at the carby and see if there is a problem with the mixture or if  only one carby is getting fuel and maybe go for a drive again and when it starts to 'starve' pull the choke cable out and see if that improves things. The choke will move the jet tube down and allow more fuel past the needle.

Also watch your temperature gauge to see if the temp goes up when it starts to starve.

Terry

https://photos.google.com/photo/AF1QipMSAinSz2Z0DtUl9jgXxddu38bZRy1N9MER-CJh

I'm thinking this flow should be OK Terry? If so saved me a few Dollars!!  :) Haven't had a chance to do another test drive with the other suggestions yet. Cheers, Jim

jimivo

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Re: Twin 1 1/4 Su's again!!
« Reply #9 on: September 26, 2018, 05:16:09 PM »
So How come the carbs don't have a return to the tank ????

jimivo

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Re: Twin 1 1/4 Su's again!!
« Reply #10 on: September 26, 2018, 05:19:02 PM »
Hope you get it sorted Jimivo it would be great if you could join us for IMD.
We have only seen you driving in the opposite direction on the other side of the road :)


Alan S  8)

 Yes Alan , I was miffed when I saw you guys that day. I thought I had missed the run , I thought it was the Month before !!

Terry

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Re: Twin 1 1/4 Su's again!!
« Reply #11 on: September 26, 2018, 06:10:41 PM »
So How come the carbs don't have a return to the tank ????

The needle and seat in the top of the float bowl shutdown the flow when the required level is reached and the pump(s) go into neutral and don't send any more fuel through until the pressure drops because the float has dropped and opened the needle/seat valve. The fuel is drawn into the carby by the flow of air and not and pressure of the fuel line(hence the low psi requirement of the pumps) so there would never be any fuel to return.

A float bowl lid with two opening, inlet and outlet, are a later thing where if the needle/seat fails to stop the fuel and the float bowl fills up it will escape down the outlet and is supposed to get soaked up by the charcoal in the canister. On the early type fuel would become pressurised in the bowl leak out onto the exhaust. It is a warning thing to tell you that your engine is getting flooded with fuel.

Terry

   
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is.


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