Jonathan Saunders Posted June 27, 2023 Report Share Posted June 27, 2023 Hi guys. I have read a great deal about fuel vaporisation on hot engine on hot days. I am experiencing similar symptoms. Before I commit to any mods has anyone ever taken carb temperatures, fuel line temperatures or fuel pump temperatures to prove out this theory. I am thinking of getting infra red contactless digital thermometer to check surface temperature of various components in the fuel system. Hoping this will point me to the exact position in the fuel system before I make any rash decisions. Your experiences greatly appreciated. Jon Saunders Link to comment Share on other sites More sharing options...
johny Posted June 27, 2023 Report Share Posted June 27, 2023 Can you tell us exactly what youre experiencing? Link to comment Share on other sites More sharing options...
Jonathan Saunders Posted June 27, 2023 Author Report Share Posted June 27, 2023 Car runs great on cool days. On hot days 26 degrees engine starts to show signs of fuel starvation. Fuel seems to get beyond the fuel pump as I can see it through glass filter. Engine cuts out will not restart. Open bonnet for a few minutes crank engine for about 30 secs and engine restarts. Link to comment Share on other sites More sharing options...
johny Posted June 27, 2023 Report Share Posted June 27, 2023 All completely standard is it? stromberg 150 carbs, standard airfliter box with hoses drawing from side of radiator, metal fuel pipe running from mechanical pump around front of engine, mechanical radiator fan etc Link to comment Share on other sites More sharing options...
Jonathan Saunders Posted June 27, 2023 Author Report Share Posted June 27, 2023 Not standard. Twin air filters . Fuel pipes metal and ethanol proof rubber. Standard fan. Standard fuel pump. Non water Coolant in rad. runs at normal temp no overheating ever even in heavy traffic jams. Link to comment Share on other sites More sharing options...
johny Posted June 27, 2023 Report Share Posted June 27, 2023 Wonder if the air filters are making a difference as my mk1 with standard air box and hoses has been in southern spain with their summer temperatures and no similar problems. The only other thing I can think of is what are you cylinder compressions like hot? oh and how is your mixture? If you run slightly rich, hot weather will exacerbate the situation making starting harder (later model carbs went to temperature compensators)... Link to comment Share on other sites More sharing options...
Jonathan Saunders Posted June 27, 2023 Author Report Share Posted June 27, 2023 Carbs are balanced and tuned. Plugs show light brown deposit. Compression both hot and cold within triumph tech spec. All of the above can be verified with test equipment and was checked last Sunday. What I can’t verify is actual component temperatures. That’s why I am considering an Infrared thermometer. Had anyone ever tried this to find the offending area?? Link to comment Share on other sites More sharing options...
johny Posted June 27, 2023 Report Share Posted June 27, 2023 well as I say I have the same car and havent got an offending area. Apart from the airfilter arrangement the other difference is that I have a decent electric rad fan which although many will say is not necessary I find does help to keep under bonnet temperatures down. As an experiment you could try running without the bulkhead rubber seal in place so leaving a gap for hot air to escape... Link to comment Share on other sites More sharing options...
Josef Posted June 27, 2023 Report Share Posted June 27, 2023 Are you able to replicate your issue stationary and with the bonnet raised? That obviously will change the engine bay heat distribution so might invalidate your intended test. Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 28, 2023 Report Share Posted June 28, 2023 i think you will find this is running on the rich side of normal not helped by twin filters my 1600 with unwrapped 631 would idle for an hour on Mot and not miss a beat you do need a cold air supply not hot under bonnet high ambient air, sorry thats just asking for what you are getting you can see from the replies most do not have a problem i suggest you swap back to a std air box with cold air pipes fitted and check the running and use std needles what fitted if you have some pancake filters as these really upset running mixtures and there are few needle options available to give proper running Link to comment Share on other sites More sharing options...
johny Posted June 28, 2023 Report Share Posted June 28, 2023 yes I know you can get heat shields for the carbs and people have changed the route/wrapped the fuel pipe and even gone for electric pumps but if one standard car can run without vaporisation then all other standard ones should be able to do the same... Saying all that I will run my electric fan on for 30 seconds after stopping from a hot run - have to be careful not to overdo it though or I need choke to restart! Link to comment Share on other sites More sharing options...
Iain T Posted June 28, 2023 Report Share Posted June 28, 2023 In my view the pancakes are not the problem. Yes in hot weather they possibly can make the engine tick over rich but it shouldn't stop the engine. I would check the fuel pipe runs to see if the joins are tight and anything is too close to the block and getting toasty. I have heat shields fitted to my carbs which could well fix your problem. Iain Link to comment Share on other sites More sharing options...
68vitesse Posted June 28, 2023 Report Share Posted June 28, 2023 In the recent hot weather found my 2L Mk1 Vitesse, standard but with electric fans, very difficult to restart when hot if left for a short time but fine if left for an hour or so. Had moved a glass type filter from just after the tank to just before the carbs. moved it back and problem went away. After one run before moving it back parked car in garage when looking about five minutes later fuel filter empty of fuel and petrol in glass top pump boiling, an hour later filter full of petrol. A few utube videos with same restart problem stated restart problem due to very rich mixture, as above, some had gone to the trouble of fitting a filer vapour separater with a return line to the tank. Regards Paul Link to comment Share on other sites More sharing options...
Mark B Posted June 28, 2023 Report Share Posted June 28, 2023 The SU Hs6 carbs fitted to my Vitesse were getting pretty hot, sitting above my 6-3-1 manifold, so I made up this heat shield. Temps before and after, traveling same route/speeds. Made a difference, but on very hot days short stop start journeys, after turning the engine off for several minutes under bonnet temps rise and the starter sometimes trips over itself trying to start, always starting first spin, but I will be adding an extra air duct to funnel air from the front grill. Also have a kenlow fan fitted. Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 28, 2023 Report Share Posted June 28, 2023 just make sure the bubbles are not from a crap hose on the H & V tank outlet sucking air its a common culprit for bubbles Pete Link to comment Share on other sites More sharing options...
Ian Foster Posted June 28, 2023 Report Share Posted June 28, 2023 My experience of vapourisation was traced to the fuel boiling in the pump. I have now replaced the mechanical pump with an electric Huco sucker and rerouted the fuel line to the carbs around the back of the engine. For my sins, I do have K&N pancake filters, but have plans to rehome them in a new airbox with cold feed. (a winter project....maybe even this winter!) +1 for heat shields. Ian Link to comment Share on other sites More sharing options...
Jonathan Saunders Posted June 28, 2023 Author Report Share Posted June 28, 2023 Thanks Ian i have ordered an Infrared thermometer which I am going to place under the bonnet during different weather conditions and pointing at various parts of the engine bay. Ie carbs. Pump , fuel line by top of rad etc. hoping to pin point areas that record 200F plus which is the vaporising point of E5 Fuel. I can then decide where to spend money on curing the problem. Link to comment Share on other sites More sharing options...
68vitesse Posted June 28, 2023 Report Share Posted June 28, 2023 4 hours ago, Pete Lewis said: just make sure the bubbles are not from a crap hose on the H & V tank outlet sucking air its a common culprit for bubbles Pete All fuel rubber hoses recently replaced with gates barricade from club shop, no sign of bubbles when engine running. Has to be boiling petrol. Regards Paul. Link to comment Share on other sites More sharing options...
Iain T Posted June 28, 2023 Report Share Posted June 28, 2023 2 hours ago, Jonathan Saunders said: have ordered an Infrared thermometer which I am going to place under the bonnet during different weather conditions and pointing at various parts of the engine bay. Ie carbs. Pump , fuel line by top of rad etc. hoping to pin point areas that record 200F plus which is the vaporising point of E5 Fuel. I can then decide where to spend money on curing the problem. If it runs ok at lower temperature it must be vaporisation. Make sure you have the thick fibre heat spacer between to inlet manifold and carbs. Fitting heat shields is a must have. I used a rubber lined P clip that holds the fuel pipe at the front of the engine. I also found my pipe from the pump to the carbs was virtually touching the block. A small tweak to the pipe sorted that. Best of luck! Iain Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 28, 2023 Report Share Posted June 28, 2023 do you use E5 or E10 ??? Pete Link to comment Share on other sites More sharing options...
johny Posted June 28, 2023 Report Share Posted June 28, 2023 20 hours ago, Jonathan Saunders said: Car runs great on cool days. On hot days 26 degrees engine starts to show signs of fuel starvation. Fuel seems to get beyond the fuel pump as I can see it through glass filter. Engine cuts out will not restart. Open bonnet for a few minutes crank engine for about 30 secs and engine restarts. ok well if the problem is heat affecting fuel it must be in the carbs as its doing it running. Under these circumstances its unlikely to be in the fuel line because this is pressurised when the pump is in operation making it even more difficult for vaporisation to occur. Also we can discount the pump itself as you can see it delivering fuel. So once the engine has cut out I take it that if you dont open the bonnet its pretty much impossible to restart? Link to comment Share on other sites More sharing options...
Jonathan Saunders Posted June 28, 2023 Author Report Share Posted June 28, 2023 Thanks everyone for relating your experiences with fuel vapour lock . This week end I will start rechecking all fuel pipe joints to ensure they are sound. I will then run the car stationary hood up and take temps. I will then run the engine stationary with hood down and take temps. If no vapour lock problems I will move on to taking temps while car is moving. This will be tricky but have borrowed a thermometer with a probe which I fix to various parts of the engine and observe while driving along. Hoping to replicate vapour lock on hot days so I can pin point where to make a modification. 1 Link to comment Share on other sites More sharing options...
daverclasper Posted June 28, 2023 Report Share Posted June 28, 2023 When fuel gets hot by under bonnet temperature, what is the effect on combustion. For example, I have read that the air bubbles make the mixture weak. Is this correct?, or other info about how this can cause the hot day traffic jam stumbling/difficult starting please Link to comment Share on other sites More sharing options...
Peter Truman Posted June 28, 2023 Report Share Posted June 28, 2023 I realize were talking Vitesse and Stromberg Carbs here, but just to expand members info my daughters Mk2 Spit had serious vaporization issues around 15 years ago it was only after making DIY heatshields & trial fitting them I realized what the problem was the float bowls weren't vertical they had rotated towards the standard tubular exhaust causing the vaporization. The plastic bush in the carb which orientates the fuel bowl on the rear carb had failed allowing the bowl to rotate, easy fix with minimal dismantling was to replace the plastic sleeve/bush the bowl was then vertical, there are different bush's available to suit different carb and inlet manifold inclinations eg BMC Mini etc, the bush's are colour coded depending on the required float bowl inclination. My DIY heat shields are separate for each carb and are mounted at the rear of the carb to manifold flange so they can be removed for access without disturbing the carbs ie studs replaced with threaded bar extending behind the manifold flange, see photo. I've never found this mod necessary on my Mk2 Vitesse, it's completely standard, with cast iron exhaust manifold. Link to comment Share on other sites More sharing options...
johny Posted June 29, 2023 Report Share Posted June 29, 2023 Interesting Peter, when did the vaporisation manifest itself, heat soak on stopping the engine or with it running? Link to comment Share on other sites More sharing options...
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