Lagondaforum » Engine » Carburetion and Fuel

davidbracey	Dec 05, 2013 11:07 pm
Subject: LG45 Fuel pump Hello everyone. I've just posted some more photos of my LG45 saloon restoration in the members gallery if anyone is interested I have a query regarding fuel pumps. My car has a single SU Fuel pumps which looks tiny to me. I have two of these on my 1.5 litre 4 cylinder Aston so can't quite believe that one is sufficient to keep a 4.5 litre 6 cyclinder engine's thirst quenched. The Burlen website helpfully suggests a double fuel pump (See link http://sucarb.co.uk/carbspec/carburettor/pumps/id/1340/ ) but I don't think a long pump like this would fit in the compartment behind the firewall. Can anyone shed any light on this. I am tempted to fit two single pumps in parallel. Many thanks, David

davidbracey

Dec 05, 2013 11:07 pm

Subject: LG45 Fuel pump

Hello everyone. I've just posted some more photos of my LG45 saloon restoration in the members gallery if anyone is interested

I have a query regarding fuel pumps. My car has a single SU Fuel pumps which looks tiny to me. I have two of these on my 1.5 litre 4 cylinder Aston so can't quite believe that one is sufficient to keep a 4.5 litre 6 cyclinder engine's thirst quenched.

The Burlen website helpfully suggests a double fuel pump (See link http://sucarb.co.uk/carbspec/carburettor/pumps/id/1340/ )
but I don't think a long pump like this would fit in the compartment behind the firewall.

Can anyone shed any light on this. I am tempted to fit two single pumps in parallel.

Many thanks,

David

bill	Dec 10, 2013 5:40 pm
Subject: Re: LG45 Fuel pump My advice for what it is worth. Fit a single one at the back of the car (a "pusher") and a single one at the front (a "puller"). Also fit a pressure regulator (at back of car out of sight) and set it at 2 psi. The SU pump normally delivers fuel at about 4 psi which is far too high (in my H.O.) and can cause flooding. Quantity delivered is perfectly adequate. I have used this system on my LG45 without problems for some years - so far !

bill

Dec 10, 2013 5:40 pm

Subject: Re: LG45 Fuel pump

My advice for what it is worth. Fit a single one at the back of the car (a "pusher") and a single one at the front (a "puller"). Also fit a pressure regulator (at back of car out of sight) and set it at 2 psi. The SU pump normally delivers fuel at about 4 psi which is far too high (in my H.O.) and can cause flooding. Quantity delivered is perfectly adequate.
I have used this system on my LG45 without problems for some years - so far !

davidbracey	Dec 10, 2013 6:06 pm
Subject: Re: LG45 Fuel pump Hi Bill, that is a very interesting solution. I presume you modified to this arrangement after having difficulties. Did the dual pump system not deliver the correct flow rate or was the pressure too high causing flooding? David

davidbracey

Dec 10, 2013 6:06 pm

Subject: Re: LG45 Fuel pump

Hi Bill, that is a very interesting solution. I presume you modified to this arrangement after having difficulties. Did the dual pump system not deliver the correct flow rate or was the pressure too high causing flooding?
David

bill	Dec 11, 2013 7:06 pm
Subject: Re: LG45 Fuel pump Hi David I installed this system when I rebuilt my LG as I had put a similiar one on my M45. I modified the fuel pressure only because I had been experimenting on another car (1950s Jaguar engine) and realised that these SU pumps deliver fuel at far too high a pressure. It is about 4 psi and I ascetained that 2 psi is more than enough provided that you have the flow rate. I suspect that you could probably even reduce the pressure to 1.5 psi as long as the flow rate is sufficient. The standard pressure is in my opinion far too high for the simple SU carb needle valve and this is one of the causes of flooding (possibly Burlen will not agree with that !). I made up a simple test rig to check the fuel pump pressure so that I knew what I was dealing with. I used a "Pro-Flow" Regulator (about £30). It is hidden away out of sight on the tank in the outlet pipe. It is very easy to adjust and you can experiment as to what suits your car (or your driving style !).

bill

Dec 11, 2013 7:06 pm

Subject: Re: LG45 Fuel pump

Hi David
I installed this system when I rebuilt my LG as I had put a similiar one on my M45.
I modified the fuel pressure only because I had been experimenting on another car (1950s Jaguar engine) and realised that these SU pumps deliver fuel at far too high a pressure. It is about 4 psi and I ascetained that 2 psi is more than enough provided that you have the flow rate. I suspect that you could probably even reduce the pressure to 1.5 psi as long as the flow rate is sufficient. The standard pressure is in my opinion far too high for the simple SU carb needle valve and this is one of the causes of flooding (possibly Burlen will not agree with that !). I made up a simple test rig to check the fuel pump pressure so that I knew what I was dealing with. I used a "Pro-Flow" Regulator (about £30). It is hidden away out of sight on the tank in the outlet pipe. It is very easy to adjust and you can experiment as to what suits your car (or your driving style !).

Bill Inglis	Dec 14, 2013 9:02 pm
Subject: Re: LG45 Fuel pump HI David We’re another who had to replace the fuel pump on our LG45. The replacement SU pump I bought was sold as a “SU double electronic AZX1400”. Also cast into its side is “AUB 650”. It looked almost identical to the old one, and fitted straight in. However it occasionally had trouble priming and its output pressure caused several leaks at the SU carburettors. And then a friend produced copies of old SU pump service leaflets. I began to suspect that the new pump was a “pusher” model and not a “sucker” model, so tried fitting it in the boot just above the petrol tank, plus a pressure regulator adjusted to about 2 psi in the fuel line to the carburettors. That seemed to fix both the priming problem and too much pressure arriving at the carburettors, and we’ve now done about 7000 miles with no more fuel supply problems. I think if I did it all again I’d make sure that the pump I was being sold was a sucker model and not a pusher model. Hope there is something in all that which is helpful, Bill Inglis

Bill Inglis

Dec 14, 2013 9:02 pm

Subject: Re: LG45 Fuel pump

HI David
We’re another who had to replace the fuel pump on our LG45. The replacement SU pump I bought was sold as a “SU double electronic AZX1400”. Also cast into its side is “AUB 650”. It looked almost identical to the old one, and fitted straight in. However it occasionally had trouble priming and its output pressure caused several leaks at the SU carburettors.
And then a friend produced copies of old SU pump service leaflets. I began to suspect that the new pump was a “pusher” model and not a “sucker” model, so tried fitting it in the boot just above the petrol tank, plus a pressure regulator adjusted to about 2 psi in the fuel line to the carburettors.
That seemed to fix both the priming problem and too much pressure arriving at the carburettors, and we’ve now done about 7000 miles with no more fuel supply problems.
I think if I did it all again I’d make sure that the pump I was being sold was a sucker model and not a pusher model.
Hope there is something in all that which is helpful,
Bill Inglis

davidbracey	Jan 31, 2014 6:18 pm
Subject: Re: LG45 Fuel pump Thanks for all the helpful advice and comments. It seems that there has been much frustration within the club brought about by fuel delivery. I have plumped for a twin SU AUA11EN pump mounted in the original position under the bonnet which Burlen have assured me is the correct option. I will find out shortly and report back. In the meantime if anyone can help me with a window handle I would be very grateful as this is almost the last piece of my Lagonda jigsaw puzzle that I need. Thanks again for your time and help. David

davidbracey

Jan 31, 2014 6:18 pm

Subject: Re: LG45 Fuel pump

Thanks for all the helpful advice and comments. It seems that there has been much frustration within the club brought about by fuel delivery. I have plumped for a twin SU AUA11EN pump mounted in the original position under the bonnet which Burlen have assured me is the correct option. I will find out shortly and report back.

In the meantime if anyone can help me with a window handle I would be very grateful as this is almost the last piece of my Lagonda jigsaw puzzle that I need.

Thanks again for your time and help.

David