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MG MGB Technical - Fuel tank replacement

Hi all new to forum,please forgive me if this has been asked before but i cant find the sepcific query that i have,so... a couple of associated probs im having...
i have just bought an mgb gt with view to restoring.it came with a new petrol tank ( not fitted )and all the relevant fittings.i have fitted new sender unit to tank and am now wondering if i have put it in the right way up! , float with wire to bottom?? also upon getting under car i cannot locate a threaded banjo nut(?) to connect to fuel tank! the previous owner i suspect has done away with this as he has a piece of rubber/plastic pipe from fuel pump to a gallon container in boot!! can you please confirm is there meant to be a metal pipe from fuel pump with a nut that should attach to fuel tank? can this section be bought on its own? also all the connecting pipes to carbs have been cut and adapted for this bastardised set up.i have a manual with car but is for the older models and not much help.i can see the two inlet/outlet ports on pump but both have plastic pipes to them?!
any help greatly appreciated many thanks
i will go and take pic if that will help?
l c clayton

pic of fuel pump


l c clayton

this is what is currently fitted! not my doing lol


l c clayton

LC - Holy cow! that's a disaster waiting to happen! No wonder you are in a hurry to get the tank replaced.

There is no banjo fitting on the tank. There is an elbow compression fitting on the upper right end of the tank (near the back of the tank. The fitting is a 1/4 BSP compression fitting that should match the fitting on the end of the fuel line. I would suggest checking the fitting on the end of the fuel line to make sure that the nipple on the end is not damaged. If it is, it will not seal properly. Look for any nicks in the angled surface of the nipple or a circumferential ridge on the angled surface.

While you are under the car, there appears to be a small tube (1/4" OD) hanging down from the vent spigot on the pump. That tube should be replaced with a length of tubing that can be routed into the boot (hole with a grommet in the front right hand corner of the boot floor). The purpose of the vent is to relieve air pressure from the back side of the fuel pump and if any water gets into that area, it will cause severe rusting and stop the pump from running, which is the reason it needs to be routed into the boot. If the tubing seen in the picture you attached is just hanging down as it appears to do, it is in the path of any water being splashed under the car. See the article, SU Fuel Pump Vents in the SU Fuel Pump Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

If you have the late tank/sender, then all you'll need is some 5/16th rubber fuel hose from the pump to the sender/pickup unit. Secure with jubilee clips. There will be no screw fitting.
It's also possible the guy got the late tank and earlier sender, in which case there will be no fittings...

Regardless of what is bought/fitted, the correct set of parts can always be obtained from places like Moss and the owners club, so no panic.

The sender should only fit in one way, there's a cutout in the hole with matching notch on the sender.

Those plastic pipes look a bit dodgy too. Get some quality rubber fuel hose (and the proper steel/copper pipe to go front to back on the underside of the car if it's missing).
RoadWarrior

Thanks for your replies,just to clarify the new tank does have an elbow threaded fitting,but there is no copper pipe with nipple and attached nut to screw onto this,i presume he cut this away and replaced with said black tubing*.i have now ordered this section of copper pipe and a piece of braided hose /banjo fitting to connect to pump.hope this is all i will need.oh and washers.
(*the bottom bolt on pump, on pic ,goes straight to a fuel filter and then the smaller diameter pipe to tank in boot)this should have the braided hose connection running to copper pipe then to tank-shouldnt it!
thanks again

ive also got other queries ( 1st project you see!) should i post these seperately?
l c clayton

Your car seems to be a rubber bumper model. As has been noted, the connection is from the pick up tube/sender unit to the fuel pump via rubber fuel hose. The fuel hose fits over the nipple on the late model sender unit/pick up tube (which should have a white, plastic "sock" on the end that goes inside the tank) and is secured with a hose clamp (jubilee clip?). The line runs forwards to the fuel pump where it attaches, with a second clamp, to the banjo fitting on the inlet side of the pump. Your tank may have a threaded fitting, near the fuel filler neck, which hooks up to a vapor seperator on the right hand side of the fender inside the trunk (boot) area. At least, this was the system used on the North American specification models having a sealed fuel filler cap. Do not know if it was used across the model range. If there are charcoal canister(s) in the engine compartment, it should have this fitting.

One reason the system may have been jury rigged is that the vent line from the tank to the charcoal canister can become clogged, not allowing the tank to vent properly.

More information on this subject would help us figure out what is happening.

Yes, it would be best if you addressed each issue as a separate thread. That way, it is easier to keep on track.

Les
Les Bengtson

hi, yes its a 1977 rubber bumper model.im a bit confused as the new petrol tank had a large opening for the sender unit which is fitted and requires electrical connection to.However there are no other openings to connect fuel line to other than this threaded fitting by filler neck,you say this is a vapour vent line? (perhaps)
can you expand on the sender unit/pick up tube,is this the same thing as the sender unit?sorry to be so stupid but im new to this.
it would have been far simpler if it were just a rubber hose to push over a nipple on tank but i believe metal pipe should run to tank with nut pre attached.also pipes at carb end have been cut so as this "adapted system" works (straight thru from pump to carb)! but i will address this once new tank connected.
thanks for all your replies so far
l c clayton

my tank is identical to pic bottom left


l c clayton

The photo in your illustration is reversed. It should show the filler neck on the right hand side of the tank.

The threaded fitting near the fuel filler inlet is the tank vent and it is fitted with a pipe, secured by a nut through which the pipe passes, having a 90 degree bend. This fitting connects the tank to the vapor separator located inside the trunk. The other line from the vapor separator goes forwards to the charcoal canister inside the engine compartment.

The sender unit consists of the sender with wire arm and float and the fuel pick up tube having a plastic "sock" type filter on the end. It goes into a hole on the upper, right hand side of the fuel tank and a threaded ring is used to secure it firmly to the tank. There is a flat, round rubber ring that fits between the sending unit and the fuel tank with the threaded ring turned to tighten the sender in place against the gasket and tank. The sending unit has a single plated tube coming from it to which the fuel line is secured. The fuel line goes to the banjo fitting on the intake side of the fuel pump.

The outlet side of the fuel pump goes to a hard line, via a rubber hose and banjo fitting, thence forwards to the carbs via a fuel filter located on the firewall of the engine compartment just above the shelf area.

Les
Les Bengtson

AS David Dubois said, Wow, what a possible disaster. Everyones advice is great, but also as per David Dubois's web site, consider the addition of a fuel petcock or ball valve into the system. This will make working on the tank or fuel pumps easier in the future, remember there is no drain plug. All the best. You are not a smoker are you? Mike
J.M. Doust

LC - I would suggest getting a nipple and nut to solder to the fuel line for connection to the fitting on the pump. These are available from Moss Motors under P/N 376-415 for the nipple and 376-405 for the nut. Regarding the ball valve - see the exchange between Mike and me in the thread, "fuel pump will not pump fuel" elsewhere in this BBS (sorry Mike). Cheers - Dave
David DuBois

Nothing to be sorry for David , I am just glad we have experts like yourself giving advice. Now if we are talking teeth, I might have a few ideas there! Mike
J.M. Doust

thanks all ( les /dave) les; youve explained it spot on.i have reexamined the tank (see pic) and now now what you mean,i was confused as was looking for an actual hole,the plastic sock on mine has a spade connector there too! please see if i have fitted sender correctly.so do i now connect tube from pump to this inlet (where white sock is) sorry for this but pipes under car have mainly been cut away and there is literally a straight thru pipe from that can to carbs ( metal pipe cut off there too)my sender unit has no actual tube coming from it and none in the kit i have.can you please clarify.no wonder the prvious owner didnt fit this new tank ha ha.



l c clayton

me again!...
cant locate the fuel seperator,i think has been done away with like someone else said earlier.there is a hole by filler neck in boot but definately no fuel pipes leading to a seperator.is there another way can it just be "vented to air" or can the port on the new fuel tank be capped off or is this dangerous.cheers
l c clayton

right then,to confirm.i have spoken with mghive (uk) who assure me that i connect via copper pipe to this threaded nut (see top) it would seem that the usa system was different as would need to be connected to vapour pipe etc etc.mine will vent thru filler cap.a lot simpler for me.sorry for any confusion,parts arrive 2moz,will update you when next off work to fit.good forum thanks again for your input.

oh check out this pic,this will be same as mine!!

found on another forum,this is not my car/tank


l c clayton

UK never had fuel separator, sealed tank or any of that cobblers, but had a breathing filler cap.

The sender should only fit one way, there is a cut-out in its rim and a pip on the tank. A rubber gasket goes between sender and tank, and the locking ring over the sender.

77 and later models had the combined sender and pick-up pipe hence no separate connection for the pipe to the pump on the tank. The sender also only had one spade terminal.

Before that the pick-up outlet was in the tank i.e. upper left on your last picture, and the sender had the two terminals shown. You must get the wires the right way round on the sender, green/black on the insulated terminal i.e. the lower in that picture, black earth on the upper.
PaulH Solihull

ok thanks,the sender i have has two terminals but i have only one wire under car with spade connector ( its in top pic hanging down/dave thought was breather pipe) it has black sheath on,wonder what terminal it should attach to.i shall see if coloured under sheathing.?
l c clayton

Connect your one wire to the insulated (white bit with spade popping out) terminal. The other will hopefully earth out through the tank (this is how the later units do it) but to be sure, you could make up a small earth wire from the other spade to a convenient chassis location (the earth of the fuel pump is close by).

As Paul says, the UK never had that vent line and charcoal cannister stuff, so nothing there to worry about. Just make sure you have a vented filler cap to avoid vaccum in the tank stopping fuel delivery.

Using the copper pipe on the screw fitting will be fine, but you may have to shorten it quite a bit and shouldn't need much flexi hose as the rubber bumper pump mounting is much closer to the tank than the chrome bumper one is.
RoadWarrior

Sounds like you may have the wrong tank and sender for the car. They changed in August 1976 at chassis number 412301 (roadster) and 415001 (GT). If you find the fuel gauge doesn't work because of tank earthing - i.e. the earthing spade on the sender shows 12v - it would be a simple matter to provide an earth either piggy-backed off the one at the pump inside the boot, or taken back to one of the bullets for the reversing and number-plate lights.

However you *may* then have problems with the gauge reading correctly, as the gauge changed with the sender, and the two may need to be matched. The earlier gauges could be calibrated over quite a wide range, I don't know about the later gauges.
PaulH Solihull

ok thanks,yes ive made up an earth wire and will earth to pump in boot.i have now fitted my copper tube,going to flexi to pump.do i have to secure the pipework with clips,its only a short run of about 2 foot in total,would it be an mot requirement?
to commision the tank do you suggest putting a token amount in and then check for leaks? also will there be air in the system and if so will this need bleeding as such or will it take care of itself.
thanks for all your help so far,im learning every day!
ps: wish i had a pit!
l c clayton

If it should have clips there should be a suitably positioned stud on the body. You'll probably have to put a minimum of a gallon in to cover the pick-up, and it should be self-priming i.e. no need to bleed. That should be good enough to check for leaks in the pipe-work, then you will have to fill further - probably near 3/4 full, to fully check the sender seal.
PaulH Solihull

This thread was discussed between 26/09/2011 and 28/09/2011

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