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MG MGB Technical - Fitting a fuel filter
Hello, I was hoping to get some tips and advice on how to add a fuel filter to my 72 year MG roadster, Currently, I think my set up is as as original with no fuel filter, and a scew and nut connection on one end of a flexible braided fuel pipe attaching to the copper fuel pipe in the engine bay, just by the heater box. The other end of the fuel pipe connects to a T piece with hoses to feed the carburettors. When taking this flexible pipe off, then trying to connect up the fuel filter and new very short piece of pipe, there is now no room to for this increased length to fit back between the T piece and the screw connector I would prefer not to lose this screw fitting but I am wondering if the only way is to cut the copper fuel pipe back from the original screw and nut connection then use flexible hose, with filter in line to connect everything up. If I have to cut the copper fuel pipe, what is the best way?, I don't relish the prospect of trying to hacksaw through the copper pipe & loose the orginal fittings. Also it would be very difficult I guess to get a clean level cut on the copper fuel pipe as well inside the tight space of an engine bay! To swap a tip back, when trying to connect the two 6V batteries together through the apertures between the bays, I found that the best way was to put a 45 degree kink below the connectors, just by loosely bending the cable, so you can then pull the cable through screw and nut bit first. If you try and push the circular bit of the connectors through - No way any help with the fuel filter much appreciated ! Cheers Steve Bennett, PPS the B in LBC does'nt always stand for British ! |
S J Bennett |
SJ Depending on how much room you have where you want to cut the pipe it may be worth your while investing in a small pipe cutter used for cutting small bore central heating pipe. Have a look in B&Q plumbing section for a cutter they are not expensive and are quite small. The benifit of using this cutter is you get a perfect straight cut. You may be able to pull your pipe away from its fixings to give you room to use a small cutter, it will need to be placed on the pipe and turned 360' around the pipe to carryout the cut, the cut being made by the small cutting disc within the cutter. The cutter I have is only about 2inches in length so fits in tight situations. Colin |
C J Bryan |
Steve - Instead of cutting the end of the pipe off with the screw fitting on it (by the way, the fitting is just soldered onto the pipe), why not cur a section out of the pipe and replace it with the filter? This way you can keep the screw fitting that is there. Good luck - Dave |
David DuBois |
Colin, David, Thanks very much for the advice, set of pipe cutters ordered and will add the fuel filter in line before the screw fitting. Mind you with possibly a 30 yr old solder connection on the fuel line, it may be better to take this off and use filter plus new hose and clips in place! Happy MG'ing Regards Steve, |
Steve Bennett |
I think that if you go this route Steve that you will have too many short pieces of tubing and clips. Cut the pipe back with the cutter, that is the only way then fit a 1/4BSP to 1/4 o/d stud connector to the copper pipe. This is available from Hydrasun in brass. It is a compression type fitting and you can screw the original hose directly to it with about 2 inches cut out of it to accommodate the filter. Hope this is OK Iain |
Iain MacKintosh |
why does nobody ever suggest threading the pipping, and buying a screw on adapter to screw over it, and buying a screw in fuel filter to screw into the adapter, then run the hose to the T-fitting? |
CJD Dark |
CJD The pipe has too thin a wall to thread and threaded pipe fittings at this diameter would be few and far between. Much easier to use compression then the standard MG fuel fittings can be used thereafter. |
Iain MacKintosh |
Iain, Thanks for your note about fitting a new connector to the fuel pipe. I'd be grateful though if you could clarify what you mean by a 1/4BSP to 1/4 o/d stud connector ? I checked on the Hydrasun website, www.hydrasun.co.uk but was presented with a vast array of BSP & BSPP fittings and connectors. Does this connector then take the screw end of the flexible fuel hose? thanks for your help, Regards Steve, |
S J Bennett |
Steve, Yes the fitting is compression at one end and the threaded end fits directly to the flexible fuel hose. Have a look at the following page http://www.hydrasun.com/catalogue/page.asp?id=440 Their stock code seems to be 0036002620 priced at .88p !! Hope this is OK Iain |
Iain MacKintosh |
Why not cut the pipe back by the fuel pump? That way, you can maintain original look and you have plenty of room to work. Just a thought. Paul |
Paul Hanley |
Because any crud in the steel line (such as rust) or rubber lines (such as deteriorated rubber) won't be caught by the filter? |
Matt Kulka |
If it was me I would put the filter between the flexible hose from the pump & the fuel pipe under the car - no cutting necessary & keeps the engine bay looking original Garth |
Garth Bagnall |
I agree with the last few posts. Look at any newer car. The fuel filter is located as close as possible to the fuel tank, and before the pump whenever possible. I imagine this helps reduce damage to the pump from foreign contaminents. |
Jeff Schlemmer |
Jeff has an idea I was thinking of the other day; putting a filter between the tank and pump and maybe another in the engine bay. Might be overkill but some modern cars are using two filters (my wife's '87 Prelude for example). Any reasons for not doing this? |
Simon Austin |
Simon - Not a good idea (filter between the tank and the pump). If the filter clogs with debris, it will cause the pump to stall in a current on condition which, if the power is left on for any period of time burns out the swamping resistor inside the coil housing. Since the swamping resistor is part of the arc suppression circuit, you will wind up with a pump that eats points in a very short period of time and no one will be able to figure out why. Worse, if the pump is one of the new, all electronic units, having it stall in a current on condition with the power left on, will burn out the circuit board - big $$$! All but the largest pieces of crud will pump right through the fuel pump and be caught by a filter on the output side. Cheers - Dave |
David DuBois |
Come to that, is a filter even necessary? They didn't have one until 74 or so. |
Paul Hunt |
Agreed Paul. The factory probably gave way to popular thought and added a filter in 77 to quell the complaints. The SU pumps and carbs have relative large openings that will pass most anything smaller than a small bird and if people keep their fuel system clean with todays fuels, there is not much to clog the system. Years ago, one of the thing one looked for at the service stations was a sign on the pump that it had a filter in it to filter out all the crud that was in the fuel of the day. Today the fuels we use are probably cleaner than the water we drink. Cheers - Dave |
David DuBois |
Exactly so! I remember getting my first car - a Mini with a single SU. Next door neighbour was an AA (roadside repair) repairman and opined "You can drive a coach and horses through one of those and not get a blockage". |
Paul Hunt |
That's all very fine and I also agree that the underbonnet filter was not installed until about 1974 but I wonder why this was done. I did not install a filter in my 72 GT when I rebuilt it and naturally the whole fuel system was new except the tank. I could not prevent needle valves from sticking open causing severe flooding more times than I care to remember and was forced to fit the filter. This maust have been caused by residue coming off the walls of the tank and finding its way to the carbs. This completely solved the problem |
Iain MacKintosh |
Iain - I would have to question if the filter "solved" the problem or just masked it. It think that the telling statement was "the whole fuel system was new except the tank". The tank, from what I have seen is the biggest problem area in the whole system. That is what rusts very quickly (my tank is about 6 years old and I am beginig to see some rust particles in my system), which then travel to the rest of the system. A new or reconditioned tank that has been properly sealed will correct the problem rather than just hiding it. Cheers - Dave |
David DuBois |
I say put it before the pump. I've had many cars that used stock electric pumps and the factory placed the fuel filter before the pump and I never burnt an electric pump out. My 240Z uses an electric pump and in the 20+ years I've owned it it never burnt out an electric pump. The same with another car I own and I've had that car for 25 years. The filter protects the pump and fuel pumps generally do not like to 'push' through a filter but rather 'pull' through a filter. Of course some cars, because of the location of the fuel pumps (which are located in the tank), must push through a filter. |
Mike MaGee |
David, That's one way of putting it but then you could say that any filter is put there to mask a problem or make up for a shortcoming somewhere in any fluid system. There is no doubt that the tank is the problem but when it is still in good external condition there seems little point in replacing it when the solution is obvious. At the end of the day MG went down this same route a couple of years later. |
Iain MacKintosh |
Nor will you burn the SU pump out, but a SU that is stalled in a current on condition by a plugged filter on the inlet side will burn out the swamping resistor. You will never know that the resistor is burned out except for excessive burning of points. The pump will continue to operate as normal, except that it will start failing much sooner. Then we hear all about the "lousy SU fuel pumps". Cheers - Dave |
David DuBois |
A while back, I pumped a tank aof gas that turned out to be contaminated with rusty gunk (frustrating, since I had installed a new fuel tank). You can't remove all the contamination, so I installed two Fram G-2 filters inline, one after the other. I taped a pwerful flexible magnet to the first filter (to receive gas) to better catch rust. This system has worked wonderfully and I have continued with it. I just bought a small fuel pressure dial $10 at Autozone) with a 1/8 NPT thread and am installing it in a brass T connector before the fuel filters to keep an eye on fuel pressure. |
Steve Lipofsky |
Hi, Thanks all for the volume of postings on this, I've gone with Iain's advice (Thanks, Iain, part from Hydrasun arrived last week) and I'm shortening the copper pipeline, & fitting the new connection plus filter in line in the engine bay. That way you can get to it as part of servicing and see what's coming thru your fuel pipes! I know the point was raised about fuel now being much cleaner, and filtered etc, but there is a lot to be said for having a filter if you dont know when your fuel tank was last changed, if ever. My main reason for wanting a filter is that I've just taken my SU carbs out for a full rebuild & clean up and there was too much gunk in the fuel float chambers for my liking, but not enough as Paul Hunt says, to cause a blockage. Cheers, Steve Bennett, |
S J Bennett |
On cars that can be 30+ yrs old with God only knows what having been dumped into or exfoliating from the insides of the tank along with the (hopefully) clean gas (rust, additives, etc), there are sometimes layers of gunk and crap that have accumulated on the walls of the hard plumbing pipes from the tank and from the pump to the carbs. This stuff does sometimes flake off because of the happy cleaning action of modern fuels, so my own comfort level says I use a filter ahead of the aftermarket pump I use and before the last run of OE pipe to the fuel pressure regulator and carbs to catch this stuff. Some of the pieces caught are probably not quite as large as the Budwieser Clydsdales, but they would be large enough to block the smallest openings in the carbs. This is simply based on my own empirical experiences and circumstances, your results may vary. Small points may have big consequences. FWIW. |
Bob Muenchausen |
I'm one of the two filter crowd (three...if you count the screen in the carb!). The aftermarket fuel pump that was on my '78 when I got it has a label that says the warranty is void if used without a filter. Not that I could collect anyway, there's no brand name on the label! The pump is a cylinder just about the same size as the fuel filter. I use a filter with a metal housing between the tank and the pump. I also have a clear filter at the firewall in the engine bay. I installed this after cleaning quite a bit of rust out of the DCOE's internal screen. Since then, I've installed a new gas tank - but left the filter at the firewall in place anyway... |
J.G. Reed |
Steve, That's fine, it's a neat installation which works and looks original. Just for information and looking at your address there's a chap by the name of Ed Biddle who runs EB Engineering in Little Malvern. He specialises in full recons of SU carbs and also in Roadster complete windscreen frames already glazed and with seals. Absolutely first class job. He may be worth having a word with re your carbs. I've got a spare set and thought about sending them to him. |
Iain MacKintosh |
This thread was discussed between 13/03/2004 and 07/04/2004
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