Vapour Lock

[David Morris]

Hi there,

I took our Javelin for a run of about 20 miles, and was very pleased with her perfomance, pulling strongly and without a hitch. We needed some milk and a few other items, so I called in to Morrison's Supermarket on the way home. Fatal mistake! I don't know what it is about Morrison's but I seemed to have fuel vapourisation problems there last time I called in with the Javelin, earlier in the year. I had my suspicions that all was not well a few weeks ago, when I parked her in the garden after a run of about 20 miles and she refused to start again until she had cooled down.

Anyway, it happened again yesterday. The engine was up to quite normal temperature ( 75 degrees C ) and I left her for about 30 mins in the car park. Came back, and not a beep! I kept on returning to the car and eventually had to read quite a lot of magazines on Morrison's shelves, until the temperature had dropped to around 40 degrees C, when she started quite usually. By this time I was down to Farmers Weekly and Womens Own, which showed how long I had been there! I suppose it must have been about an hour before she had cooled-off sufficiently.

On returning home, there was time for more investigation. I found that for about 20 mins and with the engine quite warm after climbing the hills out of Bath, she would start at the first push of the button. After this, and about at the 35 mins stage, she refused to start at all. I immediately connected a spare spark plug that I have on a short lead in the boot, to the top of the coil, and cranked her by hand. The result was a nice fat blue spark, so no problems there. I then used some 'EasyStart' in the carbs, with no result - completely dead. Leaving her until the temperature gauge had dropped to 40 degrees C again, which took about an hour from arriving home, resulted in her starting first time on the button. Very strange!

It seems to be that stopping for a few minutes, say to refuel, or to go 'proper' shopping for, say, two hours, and you would never experience the problem. If stopping for a short break, danger lurks!

I can only suppose that the carbs are warming up with the heat rising from the heads, and somewhere an air lock is generated. The fuel pipes and carbs did not feel too hot and it happened with the old mechanical fuel pump, so I don't blame the electric pump I have fitted. Is this blamed on the fuel? Many people have said this is a problem with modern unleaded petrol. Why did not Easystart make a difference? Usually, this would wake a completely dead engine. I should add that I am using an additive in the unleaded petrol, made by Morris Lubricants and certified by the Federation as suitable to prevent valve seat recession.

I decided to take action today, as we have the same weather as yesterday and I have the same fuel in the tank.

I dug out two 'pancake' 12V fans, as used to cool electronic equipment and cabinets. These are about 5" in dia. I can work these from a bench power supply, but of course these would work from the 12V in the car. They send out quite a good volume of air when running.

I then arranged that these could be stood alongside the carb bowls when the car is in the garage, as a temporary measure and still allow the car to be started, but obviously not driven.

I then took the Javelin for a road run of about 12 miles, ending with climbing Midford Hill, which is about 1 in 6 and this warmed her up to full temperature of at least 75 degrees C.

Returning to the garage, I felt the carb bowls, to find they were about 4-5 degrees C, really quite cold and about the temperature of a normal fridge. This is presumably due to the change of state, fluid to a gas, within the carbs when in use.

I then installed the fans and experimented with starting the car every 15 mins. The result was a complete success! She has started every time, first time over the last hour and a half since returning. The temperature gauge in the car is now showing 30- 40 degrees C, which is where she would start anyway and did so at Morrison's finally yesterday.

I now have to think how to mount the fans on a more permanent basis. I would only need to turn them on when leaving the car for a short while, or perhaps every time I visit Morrison's! The acid test will be to return to Morrison's when I have the fans fitted!

Has anyone else had similar problems?

All the best,

David

[george garside]

Hi DAve
sounds a bit like carb icing particularly as you describe the carb bowls as being 4C 'about temp of normal fridge'. If my guess is correct it is not a question of waiting for the engine to cool down from 75 to 45 degrees but of allowing sufficient time for the carbs to warm up as the engine cools down!

Your electric fans blowing on the carbs would also have the effect of warming them rather than cooling them assuming the ambient temperature to be above 4 degrees C.

/Carb icing ends to take place on humid days & the fact that the engine is at normal temperature makes not the slightest difference to it occuring, particularly on jav as carbs are in cool air in front of radiator , The grille muff improves matters. I once had a javelin ice up its carbs at around 70mph in the middle of spagetti junction in Birmingham - deiced them by sacrificing a flask of hot tea over them!

not sure about this in your case but maybe worth looking into

george

[george garside]

Hi DAve
sounds a bit like carb icing particularly as you describe the carb bowls as being 4C 'about temp of normal fridge'. If my guess is correct it is not a question of waiting for the engine to cool down from 75 to 45 degrees but of allowing sufficient time for the carbs to warm up as the engine cools down!

Your electric fans blowing on the carbs would also have the effect of warming them rather than cooling them assuming the ambient temperature to be above 4 degrees C.

/Carb icing ends to take place on humid days & the fact that the engine is at normal temperature makes not the slightest difference to it occuring, particularly on jav as carbs are in cool air in front of radiator , The grille muff improves matters. I once had a javelin ice up its carbs at around 70mph in the middle of spagetti junction in Birmingham - deiced them by sacrificing a flask of hot tea over them!

not sure about this in your case but maybe worth looking into

george

[Keith Andrews]

In a rsent post
http://jowett.net/forum/viewtopic.php?t=720&highlight=
I have beem looking with rather intent research on octane/older engines etc.
Amounst that research/ information I gathered over resent months, there where several issues/references regarding higher octane fuels, there vapour pressues SG that result in icing and fuel lock.

It maybe worth looking into reducing octane and therefore the high content of volitile hydrocarbons in the fuel????

[george garside]

if it is icing either blocking the lower sides of the grill on the inside or if fitted with muff keeping the lower sides closed should do the trick. My thinnking behind this is that javs have from time immemorial suffered from icing occasionally irrespective of the various different concoctions of petrol sold over the
george

[David Morris]

Hi George and Keith,

Many thanks for your replies. I have experienced carb icing in the past, and had to stop on the A303 once near Amesbury, with both carbs covered in a purple ice. The problem soon went away as the engine heated the carbs and some cardboard across the grill kept the engine running warmer.

I think my problems here are probably down to the characteristics of modern fuel, as suggested by Keith. I did think of adding paraffin to lower the octane, but am a bit cautious about this. At the moment, I have ordered a couple of small, high output fans ( 50mm square ) to fit neatly against each carb bowl, as cooling the carbs seems to work in the vital hour after stopping with a hot engine.

I looked at the thread suggested by Keith ( very useful ) and noticed that 80 octane Russian fuel ran better in engines of our age. Unfortunately, they have stopped selling 'Pool' petrol here!

However, I am surprised that others have not had this problem as well in the UK. Perhaps they don't use their cars for start-stop motoring? If you used my car to drive to a day rally, and then home again in the evening, you woundn't see the problem at all.

Thanks for all the advice,

David

[Keith Andrews]

research of fuels over the last 100yrs ..The icing I came across accidently, was not part of what I was looking for.
It was in 'general' reffering to no partular makes either US or Englsh. But some did tend to be more prone than others...and included some hi octane fuels that did use lead.
DO NOT use parrafin mix. Issues with gumming unless the engine is working hard as in an old tractor working in the feilds.

[Mike Allfrey]

G'dday From The Sunny (Today) South,

There is nothing wrong with the Farmers Weekly magazine!

We had 60 mm of rain yesterday - yippee! Not much sun then.

The Peugeot 403 Solexes on my Jupiter have water heated throttle bodies and now, combined with electronic injection, the engine fires instantly at all times. No more icing concerns for me.

Regards,

Mike Allfrey