The Morrison's Effect?

[David Morris]

Hi All,
With sunshine today, I was reminded about a situation I had with my Javelin, which you might have experienced as well? I termed mine ‘The Morrison’s Effect’. I would often take my Javelin out for a short journey, which typically was when the sun was shining, and again typically this would find me parked up in our local supermarket, Morrison’s.

I would complete my shopping, with perhaps a quick cup of coffee, and return to the Javelin. Although she had started well before leaving the house, she would absolutely refuse to even cough. Absolutely dead!

What seemed to be the only solution was to return to the supermarket café and read my paper for about 30 mins. Return to the car, and as often as not, away she would go. After experiencing this several frustrating times, I concluded that it was fuel starvation caused by vapour locking somewhere in the fuel line. The carb bowls seemed almost empty, when I tried to investigate in the car park. The ignition circuit was ok and when cold, everything was fine. I wrapped the exposed fuel lines in the engine bay with asbestos rope, and that seemed to help a bit.
It became a situation I just tried to avoid. I knew that leaving the car standing in the sun, with a hot engine, would create a situation that was best avoided by just staying longer in the supermarket café, or not doing much shopping!

However, since then, I often watch revival videos on YouTube and these demonstrate the slightly more modern design of fuel systems used in the 1960’s and 70’s in the USA. These setups often have a return line leading from the fuel pump that sends surplus fuel back into the tank and ensures that the carb always has cool fuel to draw from. Even then, global warming, especially in the USA, means these 1960’s vehicles in the revival videos nowadays often suffer from vapour locking in the summer.

Was I experiencing a combination of warm fuel standing in the carbs and the immediate engine bay fuel lines, plus more modern fuel with its dreaded ethanol content? Our Jowett’s never had return fuel lines and perhaps the fuel was better in those days? Some of these ‘revival’ vehicles start up with 30 year old fuel and a fresh battery, which I am sure would not be the case today? The fuel in my Jowett generator needs to be fresh, even though I try and get the E5 fuel.

Just a thought, and I would be interested if you have experienced the same ‘Morrison’s Effect’ ?

All the best,

David

[PJGD]

David;
It is highly unlikely, but I would check that nowhere on the journey from fuel tank to the carburettors does the fuel line get close to the exhaust system. Assuming that you are in the clear on that score and if the carburettor bowls really are low on fuel when you return from the store, then it suggests that the fuel therein is evaporating out. Heat from the cylinder head is bound to conduct through the aluminium spacer into the carburettors, but why would your car be any different from any other Javelin? I would make sure that you have good paper gaskets at the spacer-to-carb interface since that might behave as a weak thermal barrier. I assume that your engine does not run any hotter than any other Javelin.

The mechanical petrol pump actuates once for every two engine revolutions, but I imagine that during your attempts at starting the engine goes through many revolutions, likely easily enough to fill the bowls. If it really is a case that the hard-to-start situation is due to the time that it takes to fill the bowls, then that suggests a problem with the petrol pump; either leaky valves or perhaps a worn eccentric on the oil pump drive shaft or a worn push rod to the pump. But none of that explains why it starts promptly from cold but not when hot. I am thinking that the fuel system is actually OK, and perhaps the ignition system has a problem with temperature. I hope that you get to the bottom of it.

[Forumadmin]

This actually is quite common. In my experience it is caused by too rich a mixture which is usually caused by float chamber valves not closing. But there can be other reasons, some of which can be a combination of factors.

[Jeremy]

Petrol mixes (as that is what they are) vary from country to country - I was in Italy in mg MG TD and never had a problem with vaporisation even in 40 degree centigrade. I returned to the UK and stopped at a supermarket and on UK bought fuel it was a struggle to re-start etc. It is certainly frustrating.

If the fuel line goes close to the exhaust system - lag it with silver heat shield - you can get this from most places like Merlin Motor Sport.

If the issue is in the engine bay which it sounds like you are describing - empty float bowls etc then the system needs fresh fuel to pump through - both electric pumps and mechanical ones struggle pumping against a gas rather than a fluid particularly if that gas is slightly under pressure. I have an electric pump on the Bradford Special located at the back of the car next to the fuel tank and so far not suffered any issues.

I have had good results from lagging fuel lines and moving the fuel lines and pipes to cooler places - this may need to go against the originality of the vehicle but will help with this issue.