AlanT Posted June 9, 2023 Report Share Posted June 9, 2023 Hi All, My Spit 1500 seems to have a vapour problem at the filter. The car runs beautifully until it’s been sat hot for a few mins. The filter is then plainly empty of fuel. Car runs fine when cold. Latest example just this AM returning from MOT (passed, tester said cleanest car he’ll see all day). Just misfires, struggles to get fuel. Could I just dispense with the filter? Pipes would still get hot. Or, would removing the engine valence help? It isn’t an electrical problem. Already fully checked, swapped out coil, condenser, points to be sure. Its not an issue in colder weather so pump flow is good. Appreciate advice. Thanks Alan Link to comment Share on other sites More sharing options...
dougbgt6 Posted June 9, 2023 Report Share Posted June 9, 2023 I don't think it's vaporisation, not with the filter just there. It's either a weak pump or a blockage from the tank. There have been a few cases of vacuum build up in the tank, but that's unusual and easily checked, open the petrol cap and listen for a woosh! Might be debris in the tank blocking fuel line. Doug Link to comment Share on other sites More sharing options...
Wagger Posted June 9, 2023 Report Share Posted June 9, 2023 I would check for air getting in at the tank outlet. When starting from cold, more fuel is sucked through from the tank. When it warms up and just idling, demand is less so more air than fuel gets in. If you put a 'See through' piece of pipe or filter at the tank outlet, you can check for the presence of fuel and air. This is a notoriously common cause because no fuel leaks out there to make it obvious. Link to comment Share on other sites More sharing options...
AlanT Posted June 9, 2023 Author Report Share Posted June 9, 2023 Thanks. Tank has been out and is very clean, pump is good. @wagger what do you mean? An air leak at the tank/pipe union? Link to comment Share on other sites More sharing options...
Ian Foster Posted June 9, 2023 Report Share Posted June 9, 2023 (edited) Alan I have had vapourisation issues with my GT6 when I was running the mechanical fuel pump and on one occasion when it 'failed to proceed' I took the top off the pump and could see the fuel boiling in the bowl, so this is a real issue, possibly made worse by modern fuels. Your pump looks to be of a later design to the GT6 one, but probably fundamentally the same. I think if vapourisation does occur it will stop the pump from pulling fuel through. An air leak in the unions between the tank and pump is also a possibility, but you report that it runs ok when not hot. I have now changed to Huco suction pump and have found this to have solved my original vapourisation problems. Having said that, I recently had issues with physical blockages in the fuel lines due to a build up of rust particles. (TSSC article pending). You have said that your tank has been out and is clean. How about yer pipes? Ian Edited June 9, 2023 by Ian Foster spelling Link to comment Share on other sites More sharing options...
Wagger Posted June 9, 2023 Report Share Posted June 9, 2023 3 hours ago, AlanT said: Thanks. Tank has been out and is very clean, pump is good. @wagger what do you mean? An air leak at the tank/pipe union? On the Vitesse and Herald, the pipe exits at the top of the tank in the boot. This piece of pipe becomes cracked and porous. May not be the same on a Spit, I have not seen a diagram of the fuel line. Link to comment Share on other sites More sharing options...
AlanT Posted June 9, 2023 Author Report Share Posted June 9, 2023 Thanks. All pipes were new at car rebuild (a year ago) but I shall examine in detail. Seems odd that it’s fine on cold days. Will also change the filter in case it’s not flowing well. Link to comment Share on other sites More sharing options...
Wagger Posted June 9, 2023 Report Share Posted June 9, 2023 I diagnosed my leaks by temporarily fitting an electric pump in the boot sucking from the tank and pushing fuel down the line. Found a porous pipe and a leak at one of the hose clips. Any leaks above the fuel level will result in bubbles in the fuel and, eventually, the siphonic action fails. 1 Link to comment Share on other sites More sharing options...
AlanT Posted June 11, 2023 Author Report Share Posted June 11, 2023 (edited) Well @Waggeryou’re right! I got the engine hot, stopped, watched as the fuel filter seemed to drain and then restarted the engine. A stream of bubbles came into the fuel filter! So, there must be an air leak at the tank pipe. No smell of petrol or obvious leaks so it’s the pipe descending into the petrol (internally) most likely. Thanks for the steer. Alan Edited June 11, 2023 by AlanT Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 11, 2023 Report Share Posted June 11, 2023 on H and V the short hose on top of the tank is the best culprit rarely leaks but being well above fuel levels often sucks air Pete 1 Link to comment Share on other sites More sharing options...
Wagger Posted June 11, 2023 Report Share Posted June 11, 2023 Just replace the flexible piece at the tank outlet and use some decent hose clips. Prime the system before starting and, hopefully, all will be well. 1 Link to comment Share on other sites More sharing options...
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