hi all, im having a problem with starting 65 s type when left hot for about 30 mins approx. happened again yesterday and while it would not start i checked for a spark at the plugs and all was ok. glass fuel bowl was full. left bonnet open and after it cooling down car started but only with pedal flat to floor so got to be fuel. im assuming fuel is vapourising in pipes from filter bowl to carbs or carb float bowls. i have today put a heat transfer tape around pipes and bowls and await to see how it goes. other people must have had this problem as it gets incredibly hot under there so has anyone cured it or made it better.

 

My 3.8 Mk 2 has and has always exhibited this behaviour…it always starts instantly hot or cold except when left (hot) for, yes, a half hour or so. It eventually fires but it takes a longer than normal cranking. I have always assumed this to be an issue of vaporisation. I would be interested in hearing theories about the cause and the cure. A minor annoyance, but an annoyance.

 

i've had similar problems, and resolved them, with another fifty-something english car of mine using twin SUs. problem was indeed traced to the overheating of the small conduit between the float bowls and jet. after a complete warm up and shutdown and after five minutes but before forty-five minutes to an hour, the car would not want to start again. IOW after shutdown there was about a forty minute time interval of misery associated with a restart.

applying a bit of manual choke, something that one would think would not help, was what was needed to start up again. and after about ten to twenty seconds of rough running it would smooth out and run normally.

of course, elevated ambient temps and a less than efficient cooling system increase the chances of its occurrence. in my case it was the innocent re-positioning of a heater hose that did it.

after i suspected what the problem was and where, i wanted to confirm it. so i laid in wait, so to speak, for it to occur again, when when it did, i pounced on the suspected area with a spray bottle full of cold water. and sure enough, after a good hosing down, she fired right up. as noted, it was clear that the re-routed heater hose was the culprit. anything unusual of a heat conductive nature in that area should be suspect: misaligned heat shield, bird's nests, dead animals (a mouse, the neighbors cat perhaps)

not sure how i would go about activating the automatic choke though. although it's possible that its default activation state is OFF, and if so, disconnecting it's power wire would turn it ON....anyway, even if it did, i would not be satisfied with a work-around. i've read that simply leaving the hood open has can be effective. again, not something i'd be happy with. fortunately, i havn't had the problem with my MK2....yet.

BTW, the reason choking works, i've read, is that the vaporized gas/air mixture is far too lean to permit combustion and choking will enrichen it. ...plausible.

 

what fuel do you use.

 

Oil Companies make Summer & Winter fuel unless you live on the equator. Winter fuel has more light ends in it to aid cold starting. If Winter fuel is used in Summer it will vapourise.

Make sure to use Winter fuel in Winter & Summer fuel in Summer. This can cause trouble in very low use vehicles.

 

funny I never had any problem restarting my 3.8 S type after driving it and then letting it sit for up to 1 hour ( before the engine went kaput).

But I had dieseling trying to shut the engine off almost everytime.

Anyway I had the carbs rebuilt by Joe Curto in NY so I hope the dieseling will have been corrected with new bronze throttle bushings and what have you that he may have done when the engine is redone.

 

To add slightly to Glyn's comment, something that's developed since our cars were new is 'whitening the barrel', getting more gasoline from the same amount of crude by mixing more light and more heavy components. This makes vapour in hot fuel lines more likely now than back in the 1960s and means it's even more important to stay in season with fuel. I usually find a burst of wide open throttle while cranking serves to clear the problem.

 

i use 89 octane gasoline with 10% ethanol in all my gasoline vehicles, not necessarily by choice but by necessity. i would consider the use of a high octane gasoline in a high performance engine that LACKS a modern, computer driven, runtime knock sensing system, but i don't own any, in running condition, at the moment.

OTOH, if and when EVER the engine rebuilder finally informs me that my '67 3.4l Mk2 engine has been installed and ready to be picked up, i will have to inquire as to the compression ratio and make a decision on that one.

 

Absolutely Peter ~ spot on.

 

Well, Glyn, I can tell you that this is not the issue with my car. First, given the velocity of the needle on my fuel gauge, I think my Mk2 has the idea that I OWN a fuel station. Second, my car is well used most of the year so in winter it uses winter fuel and by spring/ summer it is definitely on the hot weather formulation.

 

Yes Prof Gregory, It can happen on some cars where a little heat shielding may help. It is also possible that your fuel supplier/brand has too many light ends in their fuel blend ~ period.

 

And changing brands won't help because it is likely that all the Brands in your area are being fed from the same refinery. It's how the industry works. Any proprietary additives like Techron etc. are added post refining & blending.

 

Could the car be running rich? That would explain both the high fuel consumption and the difficulty with starting after heat soak. I don't have precise numbers, but my impression is/was that my 3.4 MOD Mk2 was lighter on fuel than my GM 3 speed auto V12 HE DD6.

 

I had a similar problem with my wife's grandfather's car, 59 Cadillac Coupe. At the end of the driving season before putting it away, I would filling it with gas. Winter fuel was already being dispensed. In the spring take it for a drive and stop for a little while, it would start and drive away, In about a block it would die. The fuel in the gas line would vaporize and it wouldn't restart until it cooled down or pouring water on the gas pump and steel fuel line to the carb. When the winter fuel was used up and the summer blend was in the tank the problem would go away.