Ian Cooper Posted February 12, 2023 Report Share Posted February 12, 2023 I've been struggling with starting issues and am looking for suggestions. If I leave my GT6 Mk2 (stud carbs, electronic ignition), for any time the carbs seem to drain and it takes ages to refill by cranking. If I use the fuel pump lever, and 'prime' the carbs, she fires first time every time, so where is the fuel going and why? I can't find any leaks and she runs really well. Any suggestions? Ian Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 12, 2023 Report Share Posted February 12, 2023 Ah, drain back! The lever pumps a great deal more than the pump in normal operation, so it's not as bad as it seems. There is a one way valve in the pump, but it's not very effective, replacement did not improve the problem for me. You may have a leak or then there is evaporation. I have thought about an additional one way valve in the fuel line. Doug Link to comment Share on other sites More sharing options...
johny Posted February 12, 2023 Report Share Posted February 12, 2023 51 minutes ago, Ian Cooper said: I've been struggling with starting issues and am looking for suggestions. If I leave my GT6 Mk2 (stud carbs, electronic ignition), for any time the carbs seem to drain and it takes ages to refill by cranking. If I use the fuel pump lever, and 'prime' the carbs, she fires first time every time, so where is the fuel going and why? I can't find any leaks and she runs really well. Any suggestions? Ian Its impossible for the fuel to drain back from the float chambers as the fuel in there sits below the entry needle valves so would have to defy gravity to go back through them. No, the fuel in there is lost through evaporation because the chambers are open to atmosphere through a vent into the air filter box and this has to exist to allow the level of fuel to vary. So if you leave the car long enough (probably worse in warm weather) this issue is impossible to avoid and indeed I try to manually operate my pump every couple of weeks to stop the chambers from drying out completely and getting a residue build up. However Doug is right about the pump having non return valves, theres two and if either of these leaks the pump will be less efficient so at cranking speed will take longer to prime the carbs. Eventually this deteriorates until you get fuel starvation at continuous high engine loads (typically high speed up an incline) but I think your pump has still got some life left in it... Link to comment Share on other sites More sharing options...
DerekS Posted February 13, 2023 Report Share Posted February 13, 2023 I've had this phenomenon ( don't want to call it trouble ) since I bought my Spitfire 1500 years ago. When hot, she fires up immediately. Been right through the car chasing non-existent faults, starter solenoid, leads etc, ignition system top to bottom, even relaced the mechanical fuel pump like for like. Some slight improvements but nothing groundbreaking. Late last year I took the plunge and fitted a Huco electric pump, as recommended on the forum. In short, I wish I'd done it years ago, turns over a couple of times then away we go. Evaporation is the cause, I'm absolutely convinced, after a run there's a whiff of fuel in the garage for a good few days. Hope this helps. Derek. P.s. let's not forget since our cars were built fuel and modern fuel systems have changed considerably. Link to comment Share on other sites More sharing options...
johny Posted February 13, 2023 Report Share Posted February 13, 2023 Yes an electric pump will give full flow immediately unlike a mechanical at cranking speed (even a good pump) so fill the carbs faster. However many owners quite like this delay in fire up, as long as their battery is good, because it allows more time for oil to be pumped round the engine to hopefully avoid the infamous start up bigend rattle... 1 Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 13, 2023 Report Share Posted February 13, 2023 I have evaporation after a couple of months winter lay off. Occasionally, after a shorter lay off, mine will start and then die, due to the pump not overcoming the drain back quickly enough. An electric pump might be on the cards but there are a few threads on here where the pump turned out to be too powerful causing further headaches. Doug Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 13, 2023 Report Share Posted February 13, 2023 and dont forget if you have a priming lever the cam needs to be on its back or the lever gets a restricted stroke and can be quite useless if there is little resistance give the engine a short crank over to improve the cam position ( trial and error ) agree drain back might affect the initial pump action drawing fuel up the supply but the low float chambers is just evaporation unless it can jump up to the float needle by magic or on SU leak from the jet tube union on herald/vitesse always check the short hose on the tank outlet is sealed and secure its a great culprit for sucking air Pete Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2023 Report Share Posted February 13, 2023 1 hour ago, dougbgt6 said: there are a few threads on here where the pump turned out to be too powerful causing further headaches I haven't read of any problems when the Huco low pressure pump is used. It is I think rated at 2.1psi. Just don't fix it on rubber mounts bolted to a blanking plate over the original pump as mine got too hot and suffered from evaporation. I've fixed it on the horizontal ledge next to the battery and it seems much happier🤞 Iain 1 Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 1 hour ago, dougbgt6 said: I have evaporation after a couple of months winter lay off. Occasionally, after a shorter lay off, mine will start and then die, due to the pump not overcoming the drain back quickly enough. An electric pump might be on the cards but there are a few threads on here where the pump turned out to be too powerful causing further headaches. Doug I have the HUCO 13001 fuel pump and can recommend it Paul 1 Link to comment Share on other sites More sharing options...
johny Posted February 13, 2023 Report Share Posted February 13, 2023 Out of interest are people using an inertia cut off switch with their electric pumps and which ones recommended? Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 9 minutes ago, johny said: Out of interest are people using an inertia cut off switch with their electric pumps and which ones recommended? Yes I have installed an inertia switch from I think a Peugeot . Looks like this pic Paul 1 Link to comment Share on other sites More sharing options...
johny Posted February 13, 2023 Report Share Posted February 13, 2023 Neat. Is it man enough to run the pump directly or need a relay? Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2023 Report Share Posted February 13, 2023 Not yet! Paul, How did you wire it in? Iain Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 25 minutes ago, johny said: Neat. Is it man enough to run the pump directly or need a relay? I didn’t fit a relay though it’s has a 10am fuse . From memory it uses 5 to 8 amps Paul Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 32 minutes ago, Iain T said: Not yet! Paul, How did you wire it in? Iain 4 minutes ago, Paul H said: I didn’t fit a relay though it’s has a 10am fuse . From memory it uses 5 to 8 amps Paul Bolted to the side panel by the battery . Wired inline on positive side and protected by 10am fuse Paul 1 Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2023 Report Share Posted February 13, 2023 So it can be fitted vertically or horizontally? Iain Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 22 minutes ago, Iain T said: So it can be fitted vertically or horizontally? Iain Vertically as has a ball bearing in the top . In a crash the ball bearing pops out and breaks the power Paul Link to comment Share on other sites More sharing options...
Paul H Posted February 13, 2023 Report Share Posted February 13, 2023 16 minutes ago, Paul H said: Vertically as has a ball bearing in the top . In a crash the ball bearing pops out and breaks the power Paul If you meant the pump I thought it had to be horizontal Paul Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2023 Report Share Posted February 13, 2023 I meant the cut off. Cheers. Link to comment Share on other sites More sharing options...
NonMember Posted February 13, 2023 Report Share Posted February 13, 2023 That model of cutoff does work in either orientation, but vertically is preferred. It's the same as I have on my Spitfire (Facet pump in the boot, no relay) 2 Link to comment Share on other sites More sharing options...
DanMi Posted February 13, 2023 Report Share Posted February 13, 2023 I simply think of it this way. If the engine hasn't been run for long enough for the fuel to evaporate the oil will also have drained back so I just think of the few extra turns of the engine as being a good thing as it lubricates the engine before it fires. 1 Link to comment Share on other sites More sharing options...
Iain T Posted February 13, 2023 Report Share Posted February 13, 2023 Even with a Huco if I haven't used the car for some time it still takes at least a couple of long pills to start and that's priming the carbs. I think more than enough to circulate some oil. Iain Link to comment Share on other sites More sharing options...
johny Posted February 13, 2023 Report Share Posted February 13, 2023 but whats the advantage of an electric pump then🤔 Link to comment Share on other sites More sharing options...
Ian Foster Posted February 14, 2023 Report Share Posted February 14, 2023 On my Mk2 GT6, I changed to a Huco electric pump due to problems of fuel vaporisation in the mechanical pump. After a 'failure to proceed' on a hot day in traffic, I took the top off the pump to see fuel boiling in the bowl. The Huco has been very reliable and I have fitted an impact cutoff switch. I have mounted the pump on the front side of the n/s suspension turret and the impact switch on the main bulkhead behind the battery. You can clearly hear the fuel being pumped into the carbs, which is particularly noticeable after a longish period of non use. Ian 1 Link to comment Share on other sites More sharing options...
Iain T Posted February 14, 2023 Report Share Posted February 14, 2023 14 hours ago, johny said: but whats the advantage of an electric pump then It used to take many more pulls to start with the mechanical pump and I personally believe the Huco is more reliable and not over pressured than some of the new replacement mechanical pumps. Iain 1 Link to comment Share on other sites More sharing options...
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