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MG MGA - Fuel Pump
|before i order a new fuel pump for a 1960 MGA, with a MGB engine, i'm checking if the standard $90.00 pump found on eBay is going to be fine or is there any surprise's that i should be aware of--any and all comments will be appreciated--thanks, jim|
|I like to stay as close to original parts as possible and/or practical. When my original pump failed several years ago, I went with the solid state unit from Moss; it looks and sound like the original and I've not had any issues with it. I do know that many A owners have installed non traditional fuel pumps and they work quite nicely. Personal preference I guess.|
|James - If you want to stick with the original SU fuel pump, I can restore your existing pump and convert it to solid state. See the article, SU Fuel Pump Services in the SU Fuel Pump Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/ or e-mail me at SUfuelpumps@donobi.net Cheers - Dave|
|D W DuBois|
|James, are you using the MGA carbs? They require a low-pressure pump, most stock pumps put out too much and you will end up overfilling your float bowls.|
Check Barney's site for the exact pressure spec, I don't know it off the top of my head.
|Hi James - my fuel pump died last year and it turned out that it was a non standard plastic thing. So I fitted a reconditioned standard SU that I found on ebay - just the fittings/brackets were different and rubber piping needed - easy fix and now back to original look ( if you want to crawl under the car to see that is). So any standard SU will work if you are prepared for the fiddle of changing a few bits and pieces.
if you are keeping with the original design SU fuel pump for your MGA you need to make certain that it is the "HP" model. (This will also provide plenty of fuel flow for your MGB engine)
Im not sure which pump is used on the MGB, I assume it is very similar to (or the same as) the HP pump and it should also be ok.
I once fitted an identical looking SU pump from a Morris 1000 to my MGA and it worked perfectly, that is, until I got to 65 mph and then the engine began to cut out through lack of fuel flow! (I was getting about 35mpg from it which was great but I just couldnt live with the "rev limiter" effect.
I have a Facet fuel pump fitted at the moment but it works a little too well, I am in the process of fitting a fuel pressure regulator to reduce the output pressure. This is because at low engine revs it is tending to blow a little fuel past the float needle valves onto the exhaust.
|Like Colyn I have the Facet (the instructions say to use with a regulator). Mine was pushing out too much pressure , even with the Fuel King Regulator I had fitted. the regulator was supposedly set by the supplier at 3 psi. I was never able to lean out my 1800 enough. As Colyn said it was forcing too much fuel past the float valve and setting the fuel level too high. I eventually bought a pressure gauge and found it was closer to 3.5psi. I only got everything back to normal levels and correct tuning when I reduced the pressure to 1.5psi - where it sits to day and works brilliantly throughout the engine demand range.|
|"They require a low-pressure pump,"|
Low pressure is a relative thing. For SU carburetors the pressure should not be any more than 4 psi. That said, low pressure/high pressure SU fuel pumps are also relative. A low pressure SU pump put out a maximum of 1.5 psi, while high pressure SU pump put out a maximum of either 2.7 or 3.8 psi (depending on the pump you have). The early high pressure SU pumps, as used on the mgtfs and the MGA and early MGBs put out no more than 3.8 psi. The later AUF 300/AZX 1300 pumps can be had in either 2.7 or 3.8 psi.
The Morris Minors and the early T series MG (up through mid 1954) used a low pressure (1.5 psi) pump mounted in the engine compartment. It is not suitable for mounting under the car as C Firth found out.
The Facet pumps come in a range of output pressures up to around 6 psi. Getting a Facet pump that has a range of 2.5 - 4 psi is the correct way to get the proper fuel feed without a pressure regulator (which are not an ideal way to get the pressure in the correct range) Cheers - Dave
|D W DuBois|
|Just to clarify things, the SU pump for the MGA was named as the HP model by SU when it was made.|
This doesn't mean that it is delivering too much fuel pressure, it just means that it was designed to supply the bigger fuel flow that the MGA engine needs.
Like DW Dubois said, compared to modern fuel pumps it actually it is a low pressure pump, its output pressure being approx 3.5psi.
|For those entertaining the use of Facet fuel pumps, they are available in many different flow and pressures. I have found that an aircraft parts supplier is the best place to purchase.|
Have you any recommendation for a suitable pressure for a SU HV8.
A little larger than the ones used on our T-Types. We have a frontmounted Volumex SC on our TA-Special. Now just a couple of days/weeks from starting the engine. :-)
Anders & Ingvar in Sweden
|The TA has the fuel pump mounted on the firewall as far as I know, so the pump to use is the AUA 25 low pressure pump. If you are concerned about volume, you can double up the pumps in parallel like done on the TD MKII. Cheers - Dave|
|D W DuBois|
|Hi Dave, |
Maybe I should have told you that it is an XPAG 1350cc engine with a single SU HV8 17/8" carburettor mounted on the supercharger. Probably looking for around 100 hp, fitted with a special crossflow cylinderhead, that have given us a lot of problems, hopefully now sorted out.
|Anders - With that set up, I would definitely go with two AUA 25 pumps working in parallel. Particularly the newer AUA 25, low pressure pump put out considerably more volume, nearly half again more than the older ones. Cheers - Dave|
|D W DuBois|
|Hello Dave, well I have to learn to give all the information at the start of a conversation. :-)|
We have a Facet pump and a regulator and are wondering what would be the best gaspressure for the carburettor. We have a thougt that the pressure shouldnt be to high.
|Anders - The pressure sort of depends on where the pump is located. If it is on the firewall, it should be no more than 1.5 psi. On the other hand, if the pump is under the car, you can take it as high as 3.8, but I would probably be more comfortable at 2.7. My understanding is that the regulators are not real reliable down in that range, but I don't have any first hand experience with that. Cheers - Dave|
|D W DuBois|
Many thanks for your advice. We will try to adjust the pressure to somewhere between 2,5 and 3,5 psi if we can handle the regulator.
We will get a new thicker coppergasket this week, which we have made to decrease the CR a little bit. Perhaps other people with need of reducing the CR on their XPAG'S could be interested, as we have made a CAD drawing of a headgasket, round holes. We have sealed the crossflowhead due to bad casting and a lot of porosities, and also put a pipe up to get the oil straight in to the rockershaft. Hopefully all these things will give us possibilities of a testdrive in a couple of weeks, if not the swedish snow gets her before...
This thread was discussed between 13/11/2014 and 18/11/2014
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