00/63484 Posted May 21 Report Share Posted May 21 So, my 1500 spitfire engined Herald convertible is on the road again after a quiet winter indoors. Everything checked, new ethanol proof flexible pipes everywhere, carbs and pump cleaned, plugs wire wooled and presto - started first time. Went for a spin to feel young again - but scared how BIG moderns have got.... BUT now we have fuel leaking out of the top of the mechanical fuel pump - even with a replacement rubber seals. Question - The fuel pump has a screwed outlet and a push on inlet. Is this an amalgam of a 1360 pipes system and a 1500 pump? If so what is the best advice to replace the whole old pump?? ie which one should I buy? I guess I could cut off the screw end from the metal fuel pipe leading from the pump to the HS4s and put in some ethanol proof pipe to join the dots?? David F Link to comment Share on other sites More sharing options...
johny Posted May 21 Report Share Posted May 21 That does sound a bit strange as it should be either both screwed (inlet a short piece of metal pipe with rubber connector pushed on it) or neither screwed so just push on connections. I didnt think a hybrid would ever have been available😲 Anyway is the leak coming from the filter cap seal or the bolt/screw that fixes it? Is the thread of the latter ok as these being into alloy can get over tightened and strip... Link to comment Share on other sites More sharing options...
Dick Twitchen Posted May 21 Report Share Posted May 21 Sorted a friends pump leaking from the top that was due to the bolt/screw being slightly too long and bottoming out before making a good seal. Dick Link to comment Share on other sites More sharing options...
00/63484 Posted May 22 Author Report Share Posted May 22 Thank you folks. Hmm - I think the domed top edge is leaking. Yes the centre bolt looks quite long but I think it was original to the pump. I put in a new fibre washer under the bolt head too. No, the pump is probably a join up of two - fine for years and years but has decided to fail. Smelly petrol garage now...not good. So best I buy a 1500 push on connectors type pump? Not a fortune. Do they come with a spacer if required? All this scary stuff about too much pressure - a regulator between pump and carbs perhaps? suggestions? Thanks d Link to comment Share on other sites More sharing options...
johny Posted May 22 Report Share Posted May 22 Unfortunately regulators dont help much in the case where a pump develops enough pressure to overcome closed carb float chamber needle valves as at that stage theres no flow so nothing to regulate. Many think it will help but if you imagine a pipeline with a closed end that is pumped up to a certain pressure then putting a valve in the middle of it isnt going to make any difference to the pressure however much you adjust its position! If your carbs overflow and your valves/floats are all in good condition all you can do is reduce the tension exerted by the spring in the pump which is done by packing the body away from crankcase so its operating arm is moved less distance by the cam.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 22 Report Share Posted May 22 carb needle valves be they SU of Stroms have amax pressure of around 2.5psi any more and the valves get overloaded and seep fuel ,overfill the chamber and leak out the vents there is alot of history behind the pump they fitted to 1500 only they added a heat spacer and used a longer cam arm you can use a more std pump if you remove the spacer and use shorter studs , many reports on here about copy pumps sticking out over 5psi as Jonny suggests regulate the pumps stroke by adding gasket packers, you may find the plastic spacer on some MG sites , many fit a short arm pump and cut the spring down to reduce output its all a bit of a mix and match headache Pete Link to comment Share on other sites More sharing options...
johny Posted May 22 Report Share Posted May 22 Yes likely most straight forward solution is to stop the leak on the existing pump which shouldnt be impossible... Link to comment Share on other sites More sharing options...
johny Posted May 22 Report Share Posted May 22 (edited) Also while youre at it you could disconnect the pipe at the carbs and let it discharge into a container while an assistant operates the starter (with coil disconnected) to see if youre getting a good flow👍 Edited May 22 by johny Link to comment Share on other sites More sharing options...
00/63484 Posted May 23 Author Report Share Posted May 23 Paddocks are great. Good chat with a real human who came up with a solution - a new pump and gasket(s). Not expensive ...so hey. I'll keep the old one as a reminder of how things used to be. Pump should be here tomorrow. Lets hope for a bank holiday of sunshine...ok just cloudy...ok ok just no f'ing rain... Link to comment Share on other sites More sharing options...
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