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MG MGB Technical - Blocked fuel tank pickup filter
An odd one! A friend bought a barn find MGB Mk 2 a couple of years ago and it has been trouble free on numerous short trips. Recently he did a 3,500 kms trip and was plagued by fuel starvation issues related to fuel pickup - solved temporarily by blowing back through the fuel line. Draining and flushing out the tank didn’t solve the issue so he bought a new tank to solve the problem.
He removed the pickup line from the old tank and was surprised to find a very fine gauze filter on the end that was badly blocked (see photo). This pick up line and filter is not serviceable as is welded in position and there is no access panel. This doesn’t seem a good design - you would expect an external filter that is serviceable with a coarse strainer on the pickup. How many fuel tanks have been replaced because this $5 filter is blocked and cannot be cleaned? Mike |
Mike Ellsmore |
Yeah, they're a real pain in the but-
I thought I was going to be smart once and made up a tool out of a piece of 1/4" rod bent on the end into a U shape to straddle the pickup pipe--Plan was to go in through the sender unit hole and get down to the screen and push it off--tried and tried but that support bracket makes it impossible- Ended up cutting the top of the tank and got in through there and removed the screen, then had to bend the end of the tube down closer to the bottom of the tank,-resoldered the tank up and away she went- The filter itself looks very similar to the same one in carby Falcons As you suggest, there must be loads of them running around half clogged up- I had a similar issue with my elan, it had sat that long that the fuel had all evaporated away and left a wad of black gunk in the tank and on the pickup, it was as solid as a rock and wouldn't flush away with petrol,-i got it in the finish by soaking overnight in degreaser concetrate and it came out like treakle pain in the but I don't think you really need a screen in there,as long as the end of the tube is down near the bottom, you'd be unlucky to have something big enough get in the tank to block the pipe up, so a filter on the outside should do the job fine By the way, later B's not sure exactly when but around rubber bumper onwards, had the pickup tube as part of the sender unit and removeable instead of stuck in the tank--- willy |
William Revit |
I don't think it was that big a problem, I've only ever heard of problems being cased by tank sealing before this. It's dependant on there being muck in the tank of course, and changing mine at some 20 years old through external corrosion it was very clean inside. The replacement has been on there more than 20 years now.
The fuel pump has filters, and there was an engine-bay filter as well on cars with HIF carbs as they are more susceptible to debris. When I bought a Mini in the 60s my neighbour who was an Automobile Association patrol man (they didn't have 'persons' then) looked at the carb and said "You can drive a coach and horses through those" meaning it would never get blocked. It wasn't until August 1976 just into 1977 model year that a combined pickup and sender were provided. |
paulh4 |
Yeah-it's not a big overall problem as such but if it happens it's a big problem
The last one I had to do was a lady who filled up at the servo just after the tanker left, she thought she'd get some nice fresh fuel- wrong - she got a tank full of rubbish Tried flushing the tank out ,blowing back through the pickup and everything I could think of, ended cutting the top out of the tank and that screen was just chockers full of black sooty looking gunk and there was this grey jelly slime all over it, you could blow back through the pickup and it would blow a hole in the slime but as soon as the pressure was off the slime just closed up |
William Revit |
Maybe not as big a problem as pipes, pump and carbs all gunked up, in a case such as you describe. |
paulh4 |
Why not consider fitting a late model fuel sender that has a fuel pick up built in. May teke a bit of fiddling but will solve you problem .Just crimp off the original oitlet with a good sealer(JB WELD) Sandy |
Sanders |
Ahhh--Probably worth checking out Sandy I wonder if both senders have the same mounting dia. etc Disposing of the old tube and soldering up the hole wouldn't be a problem Must look into that next time - would need to make sure the senders read the same also Cheers willy |
William Revit |
I'm pretty sure the senders are the same size as the locking ring and seal are the same, and from recent tests elsewhere they do have the same resistance range - both original wire-wound and 'modern' ceramic. However the latter also seem to have the same variability as the originals of which having had two replacements on each car I've had to recalibrate the gauge three times. |
paulh4 |
I can confirm that the tank sender fitting is identical for both types of fuel pick up. On my fuel injected BV8 I needed a fuel feed and return, so I used an early tank with the fixed pick up for the feed, and fitted a late type sender with integral pick up as the return. All fitted together perfectly. |
Mike Howlett |
Good stuff Mike- that makes life easy next time |
William Revit |
The arrangement on our V8 is the same as Mike H's but our modern BMW has a fuel filter in the tank in the way Mike E describes. Makes one think ? |
Roger Walker |
Roger
The BMW setup is the same as MGZT's (BMW tank) The pump is on one side and the intank filter is on the other--accessed through holes in the floor under the rear seat The filter is in it's own canister in the tank and reasonably easy to replace if needed but caution is needed making sure the housing goes back together securely There is a pickup screen inside the pump assy. but it's not serviceable--well not really but you can get it apart if you're struggling for something to do- The screen inside the pump must be a courser mesh than the actual filter itself as I've had blocked filters and then thought the pickup would be blocked, and gone to all the trouble of dismantling a pump and found it squeaky clean There is no mention of the filter in the BMW service schedule----drive it till it drops Maybe they thought like MG that it would outlive the car--? Luckily with the BMW (and MGZT) the engine check light comes on if the filter gets marginal and it throws a code for- I think it's worded- --Long term fuel,trim reached max. threshold It'll tell you when it's ready willy |
William Revit |
Willy Appreciated - thank you Roger |
Roger Walker |
Speaking with another MGB owner who advised there is a way to fix this problem without replacing the tank. He removed the sender unit and put a mirror down the filler hole and shinning a light in the sender unit hole could see the offending filter. He then shaped the ubiquitous coat hanger into a spear and proceeded to punch holes in the screen until it had heaps of open area. After that he didn't have anymore problems! Maybe it would be worth cleaning the SU screens or replacing filters after doing this surgery and running a couple of tank fulls of fuel. After all MGAs never had this screen in the bottom of the tank and they are still running today!
Mike |
Mike Ellsmore |
Good idea Mike I have actually pushed one off the pipe with a piece of reo bent up but doing that left the pickup pipe too far above the bottom of the tank - simply spearing holes in it as described by you would leave the plastic extension in place and all should be well I now know what will happen here next time Thanks willy |
William Revit |
With that cylindrical screen on the end of the pipe the pump will start sucking in air as soon as the fuel level drops below the end of the pipe inside, clicking faster and faster as the level drops further, until it can't keep the float chambers 'full'. So the screen will have negligible effect on how much fuel is left in the tank when you finally conk out. |
paulh4 |
Mike Something else to be aware of, there are some MGB's running around that have a filter/screen screwed up into the bottom of the pump same as MGA's have--Don't know if it's an original thing or not, maybe they've had pumps put on them, but I have struck a couple of real early cars with them and the outlet pipe out the top as with MGA instead of the side as with MGB |
William Revit |
The MGB pumps I've worked on have an inlet filter internally.
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paulh4 |
Willy, I am fairly sure it is the early (3 bearing?) cars that had the MGA style of pump. At least 1963 model had that pump when I bought it decades ago when it was young enough not to have been changed. I think the pump changed when the tank did, which I recall being with the introduction of the GT. Not in the office to check the book, just relying on memory, so shoot me down if wrong! |
Paul Walbran |
Your memory is good enough for me Paul,i knew I'd come accross them but wasn't 100% sure if they were original equip. Cheers willy |
William Revit |
This thread was discussed between 10/05/2019 and 23/05/2019
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