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MG Midget and Sprite Technical - PO fuel pump bodge
Just successfully changed the clutch on My 1971 Austin Sprite feeling extremely pleased with myself.
However my euphoria was short lived as taking the engine and box out for the first time afforded me the first full view of the lower engine bay and tunnel, and the latest in a long line of previous owner upgrades put in there to kill me.
I always knew the fuel line ran through the tunnel, up in to the fuel pump mounted in the boot, per said previous owner. However I never realised it was a largely unsecured flexible pipe flapping about cable tied at one end through the tunnel then through a hole in the firewall in to the boot. Now I can see it Im going to rip the lot out and re-route using fixed copper under body. Ive been through the BBS archive and think Im clear what Im doing from carb to back axle
Im going to take the fuel pump out of the boot, and relocate it back where it should be high up underneath on the bulkhead behind the driver side on the other side of the firewall. Couple of questions I cant find the answers to.
1) Im assuming its an ignition switched live for the fuel pump, earthed to the body and Im hoping the original line there from the loom that the PO has extended off. Where does the wiring loom run for that? I cant see it as it is now on mine and am worried the PO has laid another land mine there for me
2) Are there breather pipes or fittings I need around the newly located pump (I assume tank side?) At the moment I have flex pipe out of the tunnel, to braided pipe straight on to the pump directly then what looks like the same on to the tank
Thanks in advance,
well done on the clutch change.
It certainly sounds like an amateur bodge job on the fuel line as a professional bodger probably wouldn't have gone to the effort or expense of using cable-ties.
A word of advice - do not assume anything about your car, check and double check and then treble check if with bodging, and cross-reference any information you get with at least two reliable sources, more if you can (misinformation multiplies).
Braided rubber hoses, especially modern made ones, can hide the rubber cracking or breaking down outside, and inside of course. I always use plain modern 6 or 8mm rubber fuel hose suitable for modern fuel as it's different now to 1970.
The relevant Driver's Handbook (wot came with the car when it was new) will have a wiring diagram and which fuses for what.
The pump is from the ignition switch but via bullet connectors, a join at the fusebox, wiring loom and sub-loom.
The wire would have/is white for power, and black to a body earth point.
I'm not sure where the wire branches, the boot I'd guess.
You could make up a test bulb (21w or more, for brightness of full power flow or a reliable multimeter (so not a cheap modern digital one).
The SU pumps need venting, done from boot, see recent threads on the subject.
But you might not have an SU pump in your boot, a good quality photo posted here might help with identification and perhaps other points about your installation or boot area.
1) yes it is switched from the ignition switch. As to the wiring I can't get underneath atm but someone else will know and be able to advise. Image shows some of the wiring and 'vent' in the boot on my 71.
2) yes see the Moss diagram below or the full image at
There was some discussion about those pipes ending in the boot recently and tbf mine has only one connection. The other grommet was used for the wiring for the pump!
|Thanks Nigel. I'll go take some pics shortly.
I've since chased the 'boot installation' through and can confirm the dear previous owner has taken a lump of 240v lamp flex, cube joined it in to the bullet connector off the fuse box. It then goes under the dash along the inside of the tunnel under the carpet and through in to the boot. Pump is then apparently earthed to the body. I'll take a pic of the pump especially to see what it is.
Annoyingly its running fine and the pump is working fine; my concern is with the pump in the boot if it leaks I've got fuel and vapour bomb right above the fuel tank! Plus running through the tunnel like that looks a recipe for disaster
My assumption is originally it was under the body behind the fire wall hence would have had an original branch from the wiring loom as you mentioned - can't see it though. I'll get some pics tonight
|Moss diagram (part)
|Thanks for the pics Jeremy|
Got a feeling I'm going to need one of everything from that MOSS diagram
So far PO has tried to do me in with;
- Servo 'upgrade' including unsecured brake cables across engine bay
- wrong heater blower and gaffer tape
- bonnet screw held on with wood screw
- rear leaf u bolt not done up
- bottom of wing bonded in
I wonder what is next :-)
|ETA: a photo of the fuse box wires and connections might also prove useful.|
that installation doesn't sound that bad, especially compared to some, apart from the unsecured fuel flexi-hose.
|Look on the bright side. The 'upgrades' by the PO kept the car 'alive' so that one day you could enjoy it.|
have you not tied up those wires yet, and I don't know how I missed it last time but dirt on your white paint - and who's this Johm?
|Alan makes a very good and upbeat/uplifting point.|
With enough time and experience (and frustrations) you'll probably make a few acceptable (and safe) bodges of your own, a temporary fix becomes semi-permanent or permanent.
|Shocking isn't it Nigel. You'd have thought there hasn't been the time to do it either :)|
Sorry John that was a typo.
seeing how disgraceful your wiring is I just had to find the time to tidy up my wiring - and we won't even mention that speaker, and I bet it's one of a stereo pair, more disgrace - and you put up the photos in a public domain!?
|Got it up on ramps, here are some pics (hope you are sitting down as it ain't pretty :-)|
two holes, in and out of pump through the firewall. Pump seems to beOK, doesn't leak, pumps and then stops as expected on switch on
Pump on what looks like a speaker bracket in boot (!)
Cable run from front to back - I'll have a look and see if I can find original one from loom
I can see the original mounting bracket spikes underneath, no bracket there!
|found what must be the original line cut off and bound up in tape inside the right hand boot cavity!|
|John, that's where the supply cable should be - it branches off the rear sub-loom as it loops over the top of the Off/side rear wheel arch.|
I would check continuity with a meter, using a temporary fly lead from the fuse box at the front. Its possible that part of the reason the bodging PO changed the pump location and fitted a new cable supply is because there was a fault with that original supply wire.
|On the plus side jubilee clip is nice and bright and that might be modern fuel hose that side.
No grommets on the holes through the boot wall not so good.
That pump, from the photo angle, looks like it might not have or need breather tube connections.
The bracket spikes under the car are captive threads so they'll need cleaning up and the threads cleaned and checked with a die or a few sacrificial 1/4" UNF nuts.
The loosely black-tape wrapped white wire in your photo looks suspiciously too clean, perhaps unravelled from sub-loom.
As Guy and I have put test it for live, and Guy has made a very good deduction with the possible reasoning, proves Phyllosan works. :)
John put up a photo of your fusebox and connections.
Just seen, there are two wires in the wing cavity with some sort of red connectors, what are those connectors?
|Took some more photos. I't looks like the front to back lamp wire run is spliced in at the front in to a bullet connector on a purple cable pulled from the loom (see pic - the yellow bullet end piece is then cube joined on to the lamp cable just out of shot!)
At the other end, it's a white wire cut off and loosely bound. I'l crack out my multi meter - cable must be broken somewhere hence why this has been done I guess. Where does the original loom run from front to back (wonder if I can chase through visually and find the damage?)
I have also found the remnants of an 80's MOSS style alarm under the passenger side dash. I wonder if someone has spliced the alarm in the fuel pump feed in the past, removed that alarm or its packed up and then the last owner hadn't sussed out why the fuel pump 12v is open circuit....
I'll have a look at that fuel pump. So I guess if its vented I should see in, out and then a lower diameter breather outlet
|Hi John. My car is also a 1971 Sprite.
The white wire in the boot is the correct feed wire for the pump, and the correct colour. It comes down the rear sub-loom which goes along that side of the car, starting from a group of connectors behind the top right side of the dash. One connector there will have 3 white wires, one fed from the ignition switch, one goes forwards to feed the fuse box and this third one for the pump. Either check contunuity from there to the white by the pump, or check that the white wire has 12v (or near to that allowing for voltage drop) at the end in the boot, when ignition is on.
The clamp around the body of the pump looks like it may be the correct one, re-shaped and re-used, though one cannot quite see in the photo. Certainly the rubber sleeve under the clamp is correct.
A common anti-theft modification was to put a hidden switch in the feed to the pump. So if your white wire isn't live at the boot end when the ignition is on, then either it is damaged along its route somewhere or there is a switch. The route of that cable goes behind the trim panel down the side if the o/s footwell wall, just in front of the door.Then along the floor by the inner sill and up in through into the wing cavity through an oval opening in the inner wing immediately behind the door
You mention that the cable added under for the pump comes from a purple wire. Purple should be a permanent live, which is odd because in that case the pump wouldn't switch off when the ignition was switched off. Unless that feed also had a secondary hidden switch, if the purple supply was connected to the wrong terminal at the fuse box. The horn should be off that same perm live circuit, so does it work when the ignition is off? I would discard that bodged feed anyway, and focus on sorting out the correct white feed to the pump.
you don't need to worry about breather pipes with that pump.
Alarm bells ring at the mention of a previous alarm (pun intended). This could mean all sorts of possible changes or connections but all is not lost by a long way.
I very much favour start at the battery checking and sorting all wires and connection and earths.
The PO has turned into a right PITA, the yellow wire possibly has a modern insulated bullet (but it doesn't look right so who knows) going into the 'classic' bullet connector. Possible problem with that is modern bullet is 5mm but 'classic' bullets are 4.7mm so it's a forced fit that might open the 'classic' connector too far when you go back to 'classic' bullets. But you'll probably be able to gently squeeze the ('classic') bullet connector back to fit 'classic' bullet.
The modern made 'classic' bullet connectors I've got are crap, one use only, if you remove a 'classic' bullet from them you need to bin the modern made 'classic' connector as it won't grip twice (no proper indents to hold bullets).
Once you've sorted this pump I'd suggest you start a new thread from the fusebox giving a overhead photo showing it, with the cover removed, and all the wires going to it.
The relevant Driver's Handbook will tell and show you which wires should be where on the fusebox.
Then with perhaps other photos and threads we can work out to other possible wiring issues. If you need to do more than a small amount of wiring work I'd advise you to get ratchet crimpers for classic bullets and fully insulated connectors, automatic wire stripper and a cheap 'classic' bullet closing tool as they do a better job and make the job a bit less awkward at times.
|wot I should have put -|
- you don't need to worry about breather pipes with that pump [from what I can see of the pump in your photos]. -
I think I will relocate the fuel pump first as that fuel pipe in the transmission is scaring the bejesus out of me, and now I've fixed the clutch I want to drive it!
Wiring wise, whilst working from home (!) I popped out to the garage and it seems the purple wires on my car are wired to be ignition switched 12v. And the badly wrapped white wire hidden in the boot is also working as a switched 12v so no idea why that was abandoned. Maybe its intermittent or something.
I can piece it together by pulling a wire at a time and seeing what stops working
Everything works as it should when it should (i.e wipers etc when ignition on) and not when its not on so my main worry there is what is fused and what isn't
Never knew about new and classic bullets being different mm! I bought some and soldered a new one on to the reversing switch when I did the clutch, wondering if I'm now the next previous owner from hell :-)
|I understand and fully encourage as much driving of the car as possible whilst at the same time carrying out a full staggered 36k-mile service and check - and in your case wiring checks.
Almost all posters here know a lot more than me so you won't be short of help.
I delete that I thought the purple wire may just be sacrificial cannibalised use as I couldn't know for sure and didn't want to confuse Guy's post. It does however lead me to caution you young man that whilst everything is working when it should now it might not continue to so be aware, and as it's not wired as factory convention it won't follow the diagrams.
It doesn't have to follow the diagrams to work well but if amended diagrams haven't been included and given other wiring you've found if you no longer have the alarm I'd suggest getting the wiring back to factory as much as possible as soon as possible.
But whilst enjoying your car - they need regular reasonable distance (at least 15-20 miles) use to find and sort issues and prevent further issues (along with full regular service maintenance and repairs).
with more time now I'm less settled about the purple wires being switched live if they power what they're supposed interior and boot light and horns and what else or instead of.
Taking a wire off at a time to see what stops working only gets you so far and doesn't allow for other switched or cross live supply or crossed wires/connections and any other PO peculiarity - so could give you a false lead (pun intended).
Get that fusebox photo and new thread up and at least you can start to see a bit more perhaps and without (necessarily) stopping you from driving and enjoying the car.
| <<< it seems the purple wires on my car are wired to be ignition switched 12v. >>>
If this is the case, it is wrongly connected. For whatever reason, the PO has decided to add that new bit of cabling rather than use the correct, switched white which is very odd considering it is right next to where he wanted to fit the pump! But there are other mysteries there. Purple should not be switched, and should come from the fuse box and not be connected to the ignition switch anyway. I suspect that bit has been added and has no link to the other purple supplied items (horn, interior light, boot light) supplied from a fused but not switched terminal at the fusebox.
If that wrapped white in the boot is giving a near 12v, switches off with the ignition and stands up to a robust "wiggle test" then I would use that and strip out the other bodged wiring.
I definitely agree with Nigel about driving it as much as you can. Not merely to test out the car but there's no substitute for miles covered to give yourself confidence in the car.
|Thanks both. |
I'm going to sort the fuel lines then tackle the wiring next. I did some digging and found the remnants of said alarm.... see the picture for full horror !
|At first I wondered if the purple wires plural was just a typo for single wire (used to power fuel pump) but you can't guess or assume over the net - or rely on standard factory wiring.
Was the alarm system added just an alarm or immobiliser too which might mean more added wires and/or intrusion to standard wiring.
I think as with a lot of times less is more, the less wiries the more you can see what is what. I'd start with removing any non-standard redundant wiring and connectors that have been trebled-checked as being so. Like perhaps some of those in the last photo. Don't cut any wires (at least to start with, disconnect and then remove as much as you can.
Always best to have the battery disconnected (both sides for safety when messing with the electrics - and a lot of the standard wiring is unfused from factory.
Nice securing feature on the cable-tie to pick up someone's DNA.
|Did anyone answer the original question ' what's the correct route for the white wire to the pump'?|
From the inner wing it follows the same path as the fuel gauge wires, i.e. down through a small hole in the flat wing closing panel, then it's clipped to the flange on the fuel tank, forwards and around the corner, and then follows the main fuel feed pipe up and across to the pump (once you've moved that to its correct location).
|Thanks again all. I have got myself a fuel pump bracket now, going to clean up the underside first, maybe bit of paint of some sort then relocate it.
It looks like the wiring loom has been severed; the white wire in the picture has what I assume is the fuel sender cable close by to it badly joined and heading straight down through some form bad welding out the bottom of the car, right angled through some clips on the tank before disappearing under the tank! I assume the sender cable follows the same route as the fuel pump wire out of the boot?
I will attempt to recreate the loom. Will solder or bullet the new cable in, then I'm thinking fat chance of getting the cloth braid stuff that the original has so will have to be heat shrink and some protected conduit for outside the boot?
My earlier statement of 'it all works' in terms of wiring is premature too - number plate lights appear to come on when ignition is on (!) and the headlights are off (!) and vice versa. I'll sort the pump out then start another thread for that emerging woe
the sender and pump wires are black taped together on my car., white is pump and sender will be green. DavisS gave routing info in an earlier post but mine goes through a hole in the boot floor, I'm not sure what the flat wing closing panel is (I can guess but that's not the same).
Was cloth braiding used in 1971, I thought that was earlier?
I'm not sure it will be the case with your car but often the fuse box is installed upside down which means the link that joins the red wires is in the wrong place and joining the wrong wires - but your PO could have ballsed it all up with or without this.
You may begin to see now why I suggest starting at the battery posts and moving forward on each wire, connection and circuits, the electrics can continue to work, in a fashion, despite being wrong.
Assume nothing and treble-check what you've already checked as bodgers can make a complex knitting pattern out of wiring.
Sample of link in fusebox (turned for as you look at it, on my car, from standing in front of the radiator or at r/h front wing looking towards windscreen) your wires connection might vary from factory and later from PO.
Second photo bullet ratchet crimper.
|This has been a useful reminder as I wire in an electric pump for my MK1 Sprite. I made the loom myself, basing it on a standard Frogeye version, but with a few added relays mainly to protect the 60 year old switches. But of course the Frogeyes didnt have electric pumps so I need to add a supply.
I had already included an extra green wire through to the boot area in case I ever want to add a reversing light. I followed the convention colour coding so it is switched by the ignition, but is fused. The correct fuel pump wire would be white (switched, no fuse).
On Nigel's drawing you can see the white at the top feeds the fuse box and will come from the ignition switch (or ign circuit). The second white from the same terminal goes to the fuel pump. The fuse then bridges across to the green wire terminal. My green comes from there.
It exits through a grommet in the boot floor in the void behind the o/s wheel and then follows the route Dave describes beside the tank and then over the hump.
You might be able to get the original type sleeving but a modern alternative is 'braided sleeving' plenty of sellers on ebay, fit over wiring then pull to close around the wiring and heat shrink the ends to hold it in place.
|There's a subtle difference from where David describes the grommet hole being in the flat wing closing panel ( Nigel - its the vertical inner face of the rear wing, behind the wheel). Mine is in the floor panel directly above that.
My floor panel came with my car as a replacement. It had the central locating point for a spare wheel so is a later model floor. So that is why the grommet hole is there and presumably this is where the wires exit on later model cars. I do have the hole David describes in the flat closing panel, but on my car it is on the n/s wing panel, but I know why and there is a reason for that!
|There was a discussion on the MASC facebook page recently and someone suggested using "ice hockey laces" as a fairly good imitation of the chequered woven cable covering. I've not tried it but you can see how it could be used.|
|Guy, et al, I'll try to clarify! The panel I referred to is called (by Moss) the boot floor extension panel, # 35 here:|
https://www.moss-europe.co.uk/shop-by-model/mg/midget/body-chassis/body-panels/rear-underframe-boot-floor-sprite-iv-midget-iii-1500cc-1966-79.html and the wires do go through the horizontal bit. I've seen a lot of scrapped cars and it's always there, never seen them go through the main boot floor panel.
thanks for that clarification (sorry for mistyping your name, I always miss seeing typos at the time but often notice them later).
I never thought my wires going through the boot floor was correct, nor going through the bottom triangular aperture in Part No 37.
I did ask before about the wiring routing for myself but you weren't around at the time.
That's another foot of each cable I need then.
|Yes David, I did think you were talking about panel 35, but I thought you meant that the hole was in the vertical side of this panel rather than the horizontal part. There is a hole in the side of panel 35, which is what I thought you meant, but its near the bottom and maybe is a drainage hole.|
|Guy - I think thats where mine is running now (void then through the flat plate under panel 35) |
can't see a grommet or hole though from underneath!
|Photo looking up from underneath boot floor. Fuel pump cable comes down through the grommet, around the flange of the wheel well and forward along the edge of the tank.|
The hole in the corner behind the wheel arch was pre-stamped in the boot floor panel. This is in my MK1 Sprite and doesn't have the boot floor extenders (part35). But the floor panel, which does have the hole, is from a later date as it had the securing boss for a spare wheel.
|My dinner table isn't that clean ;-)|
That's where mine is running - but I cant see the grommet any more because of the muck! I'll clean up and have a look
|John, it's only that clean because it's in the later stages of a full restoration and hasn't even been outside yet!. My other car, which is the same as yours - a 1971 Austin Sprite - is not quite so clean!
I only installed that pump wire yesterday. But when I switched on the ignition I got no machine gun noise :-(
Then I realised that the pump needs an earth wire as it's mounted in a rubber sleeve. So that's to be this morning's addition. An earth wire from the pump body.
Now I wonder, should I put a switch on the earth connection.
|My bodged up boot mounter is earthed directly to body (given my car I'd wager thats wrong too ;-)|
|I made the mounting bracket straps too, but there is a rubber anti-vibration sleeve around the pump body which stops it earthing.
This thread was discussed between 10/06/2020 and 18/06/2020
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.