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MG MGB Technical - Fuel filter
|The Mk1s didn't have a fuel filter (apart from a gauze filter inn the fuel pump). There seem to be differing views on the benefits of fitting one.|
However, if I was to fit one, (to catch potential crap from the 50 yr old fuel tank before it gets into the float needle valve)what is the consensus - a throw-away plastic filter, or a more substantial metal/glass unit with a replaceable element?
I know which would look better, but apart from that?
|FWIW I use a throw away as my underbonnet is not very standard, and the elements are more that the whole throwaway! Be aware the filter can appear full, half full, empty but still function perfectly well!|
|John. There have been many comments on type of filter to use in the past. They should be in the archives. I use the Spectre filter, which is metal end pieces with a glass body and a plastic protective sleeve to prevent possible breakage of the thick glass. I have had some of them in use for over ten years with no problems.|
One advantage of the replaceable element type (Spectre) is that it can be taken apart on the road and cleaned out. Once, on a club rally, I lost power and had to pull over to the side of the road. Tach would down with the engine, indicating a fuel system problem rather than a low tension ignition problem. Fuel filter was filled with tiny, white balls. Removed the filter, disassembled it and cleaned it out, replaced it and continued on the rally. Had to stop and clean it out twice more before getting home. Problem traced back to a fuel station with contamination in its fuel storage tank. Without the fuel filter, the problem bits would have made it into the fuel filter in the carbs, a more difficult cleaning job. Without the ability to clearly see what the problem was, I would have had to guess about what was happening. Without the ability to disassemble the fuel filter and clean it out (three times in a fifty mile trip), I would have to have the car towed home rather than drive it home.
This is my experience with six different vehicles (four of them MGs) using this type of filter. As to the claim that the glass filters are fragile and easily broken, that some have made, the other two vehicles are 4X4s used off road with never a broken filter.
|Mk2 and 'Mk3' cars didn't have one either until the advent of the HIF. When I bought my first car the AA man who lived next door pointed at the HS carb and said "That'll never get a blocked jet, you can drive a coach and horses through them". The HIF has several small orifices, and is more subject to blockages with dirty fuel.|
|When I first bought my '67 B back in '72, one of the first things I did to the car was to install an inline fuel filter under the hood. I worked in a service station for a living and part of a standard tune up was replacing the fuel filter. I saw some very dirty filters then and still do today. In '02, I installed a Moss supercharger system on the car. It came with a small disposable fuel filter. I've only replaced it once in twelve years, but I'm glad that I have it as part of my fuel system. RAY|
I have a Ryco filter on mine. The fuel level is visable through the plastic can. It has been on for probably eight years now and shows no sign of serious contamination. That may reflect filling almost exclusively in town.
I would imagine it would take a very dirty load of fuel to block it and, in that case, I would probably have to drain/refill the tank to enable the car to drive on - new/cleaned filter or not.
I have to agree with Les. A Specter Model 2369 filter is the best way to go. I'd advise installing it at the junction immediately before the fuel lines to the carburetors. If the transparent filters that you elect to use should happen to have glass housing bodies, these can be easily protected by sliding a short section of flexible transparent thick wall tubing over them. A petcock-type valve will simplify replacement in the future, preventing fuel from the carburetors from draining when the fuel line is disconnected from the filter. Another filter in the fuel line just before the fuel pump is a good idea for keeping the plumbing clear. If you ever spot debris in the one before the fuel pump you can replace the filtering element with the one in front of the carburetors. I've been running these for over ten years and have hade to replace the element only once.
One word of warning, though: The fuel tank needs to be free of internal rust. If not, instead of preventing any problems, a fuel filter on the intake side of the SU fuel pump can cause problems, the biggest being that it is an unseen problem. While the SU fuel pump will pass all but large chunks of rust without jamming, if a modern fuel filter is installed between a rusty fuel tank and the fuel pump it will then trap any fine rust particles, clogging up rather quickly. When it does, it will cause the fuel pump to stall in a “current on” condition. If left with the power on very long when this condition exists, it will then burn out the internal swamping resistor inside of the solenoid coil of the fuel pump. Once the fuel filter is replaced, everything will appear to be normal and the owner will go his way thinking that the problem has been solved. Unbeknownst to him is the fact that the burned out swamping resistor defeats the fuel pump’s arc suppression circuit and that the contact breaker points will burn out a short time later. The owner then installs a new set of contact breaker points, only to have them again burn out in a short period of time. This is the reason that a set of replacement contact breaker points will seem to burn out prematurely, so be sure to check the fuel filter on a regular basis. As a precaution, you should seal the inside of the fuel tank against rust and corrosion. Eastwood sells an excellent sealer that you simply slosh around inside of the fuel tank and allow to cure. However, be sure to blow out the screen inside of the fuel tank with compressed air before the sealant cures, otherwise the fuel pump will not be able to deliver the fuel to the carburetors. Eastwood has a website at http://www.eastwood.com .
|"... it will cause the fuel pump to stall in a “current on” condition. If left with the power on very long when this condition exists, it will then burn out the internal swamping resistor inside of the solenoid coil of the fuel pump. Once the fuel filter is replaced, everything will appear to be normal and the owner will go his way thinking that the problem has been solved. Unbeknownst to him is the fact that the burned out swamping resistor defeats the fuel pump’s arc suppression circuit and that the contact breaker points will burn out a short time later. The owner then installs a new set of contact breaker points, only to have them again burn out in a short period of time. This is the reason that a set of replacement contact breaker points will seem to burn out prematurely..."|
Couldn't have said it better myself. Cheers - Dave
|D W DuBois|
|A few years back ,when the V8 conversion BBS was more active, a lot of unfavourable things were said about the glass reusable filters.I've had 2 on my V8 MGBs over the years & will definately never fit another one.The filter area is very small for one thing & in my case ,they both sprung leaks eventually.They do have a bling factor ,but in my opinion that's all. I now use a Ryco plastic filter.Barrie E|
|"preventing fuel from the carburetors from draining"|
The fuel won't drain from the carbs if you disconnect the fuel filter, but a little will drain from the lines, and especially from residual pump pressure if the ignition has only just been turned off.
|This is why a fuel pump shut off switch is a useful thing to install in the white power supply line running to the pump. It can be easily located at the fuse box. The switch can be mounted anywhere you like and also comes in handy when storing the car for any length of time. This way, you can run the carburetors dry and not have to worry about the floats sticking and old fuel gumming up your carburetors. RAY|
|I wouldn't normally comment as an MGA owner but as a 45 year A owner who originally did 30k miles a year I have never had a filter (as Mk 1 B except H4 rather than HS4) and I have never suffered a blockage. I agree with the AA man.|
|Paul, I've owned my '67 B for over forty two years now and pretty much agree with you, but for someone just purchasing a car with little or no known history of the vehicle, installing an inline fuel filter is cheap insurance against carburetor flooding due to rust and other debris that can build up in a fuel tank over several decades. This is especially true of cars that have been sitting idle for a long period of time. RAY|
|After considering all the views, I opted to install one. My issue is as Ray describes - 51 year old tank with potential for bits of rust etc to come through. I did recently have about half a litre of fuel on my garage floor and she who must be obeyed was unimpressed! So either something got stuck in my float needle or the float hinge pin is binding.|
The filter may help, even if it is just giving me a visual of fuel cleanliness
I'm willing to bet that you could've ;)
|After 30mins of running, there was visible crud in the filter. It may well have gone right through the SU's , but I don't feel that comfortable about having fuel spewing out the overflow near a hot engine!|
This thread was discussed between 16/07/2014 and 05/08/2014
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