alextangent Posted November 19, 2007 Share Posted November 19, 2007 I was looking to run some extra wiring through the propshaft tunnel for an electric fuel pump, positioned under the rear shelf in the boot. It's going to be a serious b 🙆🏻r getting wire back down there cleanly; access is very poor. However, it struck me that my reversing lights don't work (and they're not needed for an MOT) because the gearbox switch is knackered, and I have no intention of replacing it as the gearbox is being replaced. Could I cannabalise the wiring that runs from the front to the rear, and use that for the pump circuit? There's two lights at the rear, so I could double up if amperage is a problem. Thoughts 🤔 Alex McDonald A loud 1700 SS Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted November 19, 2007 Share Posted November 19, 2007 Don't lights have to work 'if fitted' ? May need to physically remove reversing lights to avoid a scene at a future MOT ? 7 related photos Link to comment Share on other sites More sharing options...
alextangent Posted November 19, 2007 Author Share Posted November 19, 2007 Not as far as I'm aware; there's no specific test, and no mention of lights that are fitted having to work, just the statutory set. They weren't working at the last MOT, and it got through. Alex McDonald A loud 1700 SS Link to comment Share on other sites More sharing options...
DohNut Posted November 19, 2007 Share Posted November 19, 2007 My understanding is that, for example, one fog light is enough for MOT but if you have a pair fittted they must both work, which does lead to the situation where if you remove the non working one you pass N Link to comment Share on other sites More sharing options...
alextangent Posted November 19, 2007 Author Share Posted November 19, 2007 It's the case on all lights except reversing lights. Additional brake lights must work, for instance. If you remove one of a a pair of fog lights, as long as you meet the position requirement a working solo light will do. Reversing lights are not tested, except if they stay on all the time, you'll fail. Still wondering if the reverse light wiring is up to driving the fuel pump Alex McDonald A loud 1700 SS Link to comment Share on other sites More sharing options...
DaveMorris Posted November 19, 2007 Share Posted November 19, 2007 It's not that hard to get wire back there IIRC. Bit dirty though on my x-flow Remove the bit of tunnel that the gearlever pokes through end then it's pretty easy. I would use heavier gauge wire than the reversing light uses. Would also recommend fitment of an inertia switch (definitely) and relay (not a must but worthwhile)., Can't remember exactly at present but ISTR that the fuel pump pulls a decent amount of current. Dave Link to comment Share on other sites More sharing options...
Graham Sewell Posted November 19, 2007 Share Posted November 19, 2007 If you have a tunnel cover (carpet)? then run the wire from the aux position on the key switch, via an in-line fuse to the rear blukhead and then through a grommet! Cheers, Graham --- Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Julian Thompson Posted November 19, 2007 Share Posted November 19, 2007 If you DO have 2 cores handy then it is my opinion that you will be safe to run the pump from them doubled up. I think the problem you may find is that you will only have one core front to back which then splits to the two reversing lights. One core will be very marginal and not recommended as a 21 watt bulb will only draw about 3.5 amps and I guess your pump will be up around 5 to 8 amps. Link to comment Share on other sites More sharing options...
Area Representative bluenose Posted November 19, 2007 Area Representative Share Posted November 19, 2007 Alex The reverse light wire I believe is 9/0.3mm 19AWG which is rated at 5.75Amps continuous. As Julian says, it may be marginal. Nick Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted November 19, 2007 Share Posted November 19, 2007 .. or even two 21W bulbs will draw around 3.5 Amps ? 7 related photos Link to comment Share on other sites More sharing options...
alextangent Posted November 19, 2007 Author Share Posted November 19, 2007 Thanks I'll try and run a 10amp wire pair (live/earth) down the tunnel (bit of bamboo with a notch might work). Cheers. Alex McDonald A loud 1700 SS Link to comment Share on other sites More sharing options...
I.Mupferit Posted November 19, 2007 Share Posted November 19, 2007 Do make sure the wire is fixed out of the way to the tunnel side though to prevent the propshaft rubbing on it. Brent (aka Arfur Nayo) 2.3 DURATEC SV Reassuringly Expensive R 417.39 😬 Link to comment Share on other sites More sharing options...
alextangent Posted November 19, 2007 Author Share Posted November 19, 2007 The loom appears to be tie-wrapped in from what I can see down the black hole of calcutta The bamboo is an old trick my dad taught me (he was a spark) to get the wire through the existing tie-wrap or bundle of wires if it's not too tight. You make the end of a piece or bamboo half-round, about 3" or so, then a 1" or so pointy bit. Then push the pointy end into the tie wrap an inch or more, round side towards the cable. Then feed the wire into the half tunnel formed by the bamboo. Worth trying Honestly, there's that much cr@p in there it'll be well greased when it comes out the other end. Alex McDonald A loud 1700 SS Link to comment Share on other sites More sharing options...
JACK FLASH Posted November 24, 2007 Share Posted November 24, 2007 Alex, My Twin Cam came with an extra electrical fuel pump mounted at the back between the rear bulkhead and the tank. The former owner used the wiring for the revere lights as there are no reverse lights on the car. This has been working fine but ofcourse my pump only works before start up to feed some fuel to the carburettors and afterwards the mechanical pump takes over. Julian is right about the wiring. There is only 1 core going to the back and that one exits the loom at the right hand side. The right reverse light is fed and a second core runs from that point to the left hand side for the other reverse light. Why do you need an electrical pump ? Is it for solving starting problems or do your carburettors need more fuel than a mechanical pump can deliver. Jack Flash Link to comment Share on other sites More sharing options...
Ian R Posted November 24, 2007 Share Posted November 24, 2007 Alex Tie wrap your new wire to the existing wiring loom, you dont need to feed it through all the existing cable ties up the inside of the tunnel. Ian Ian (If you want to go faster, you will have to add lightness!) Link to comment Share on other sites More sharing options...
Bilbo Posted November 24, 2007 Share Posted November 24, 2007 My red top or is it gold 🤔 (I forget its the bigger one) pump is fitted to the outside of panel behind the passenger seat with a plate to stiffen up the panel. The wire just run along the bottom of the tunnel where it meets the floor on the passenger then out the panel behind the seats. I have an added switch on the dashboard next to the steering wheel so I can switch the pump off. Very handy if the battery a bit flat as you can fill the carbs then switch off to start the car. Also switch off when leaving the car parked. Really just as Graham posted 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Link to comment Share on other sites More sharing options...
alextangent Posted November 24, 2007 Author Share Posted November 24, 2007 Why do you need an electrical pump ? Is it for solving starting problems or do your carburettors need more fuel than a mechanical pump can deliver.Starting problems; fires, dies, fires, dies, fires and runs rough, then ok after about 2 or 3 seconds. The battery is getting a hammering. Plus, no filter on the fuel line, that'll get added too. Along with pressure regulator and cut-off. As to routing wiring, the prop will now be out this winter. So getting down the tunnel will be easier than anticipated. Alex McDonald A loud 1700 SS in bits Link to comment Share on other sites More sharing options...
JACK FLASH Posted November 24, 2007 Share Posted November 24, 2007 Alex, Typical problems that certainly can be solved by using a small secondary electrical pump to start up the engine. Ofcourse when you have a heavily tuned 1700 SS it might be better to put in a decent main electrical pump. You' re right to use a fuel regulator otherwise you' ll flood the carburettors. Jack Flash Link to comment Share on other sites More sharing options...
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