Fuel percolation - 2.8 3b engine

[peterblenk]

My Pf Coupe suffers from percolation when sitting for some time in traffic. This is a likelihood in modern traffic conditions - and a certainty in London where I live. We have tried a return fuel line, which helps, but the time still comes when the engine conks out, and there is no cure but to open the bonnet and wait. It only happens in the most inconvenient and embarrassing spot and will eventually give rise to a serious road rage incident. The car is too heavy for me to push it off the road unaided. Has anyone found a sure cure?

[Kaha]

I have the same problem although to lesser degree. Car usually runs well but if the engnie is turned of it is usually a pain to restart unless the bonnet is opened and wait...

If you already tried a return line, I think that the next step would be to try to get as much heat out of the engine bay as possible.
The exhaust contibutes massivly to the under bonnet heat, I have seen people install heat shields above the exhaust but I think the easiest solution is to wrap the exhaust header in isolating wrapper used in racecars.
(The nicest solution is of course to have the headers ceramicaly coated but that is a more complicated and expensive job)
For modern traffic I also think that the Flaminia fan is not so good. A good idea is to mount a electric fan close to the radiator or make som kind of air duct that directs more air through the radiator. (there are ready made solutions that can be installed without making irreversible changes to the car)

[DavidG]

This is something that worries me too, as I am hoping to use my Flaminia in hot weather when it is finished. If anybody else has experience to share, I would be grateful as well.

[lancianut666]

I bought a job lot of Flaminia spares and amongst them is a radiator that someone had fitted a Kenlowe fan to. However when checking the Kenlowe website they do not supply fan kits to fit to older cars anymore so perhaps someone has found an alternative? I tickled 12 volts across it and it burst into life but seemed to slow down the more it ran, it is more than likely full of debris inside but I can't see a way of opening the casing
Clarkey

[ColinMarr]

Fuel vaporisation in hot conditions is familiar to me from more than 20 years ago, both with a Flavia (Kugelfischer) and with a B20. In the Flavia the problem was the fuel pressure pump being mounted above one of the exhausts. Some folk resorted to baffles under the pump and/ or relocating the pump to the back of the car - I just learnt to live with it. In the B20, sometimes in hot stationary traffic the carbs just cooked away in the V between the heads until it failed – mine had a fuel return pipe and that helped a lot. I also fitted a supplementary electric pump, which also helped when called for. Happy days …

[Kevinlincs]

There are now some modern, small diameter fans than can be fitted to assist the regular cooling, available in varying sizes.
Places like CBS are a great source.
https://www.carbuilder.com/uk/fans
Thermostat controllers are also available.

Might it be worth checking that the air filter intake is actually drawing in fresh cool air rather than being stuck on pulling air from the exhaust where it would be set for winter driving? I can't recall what the Flaminia set-up is but often it's a manual adjusted lever, or could be controlled via a theromstatic valve.

Failing all efforts it may be worth rigging up a small fan with some 3 or 4" trunking that can be guided towards the inlet manifold and carbs that draws fresh air and cools the inlet assembly slightly, this may help with the fuel boiling away when stationary.

[willoroe]

I've had the same problem with my PF Coupé with single carburettor, on the Club trip to Cork recently we arrived to the event on the back of a tow truck! Of course the assembled Lancisti were able to sort the problem but it was all very embarrassing!
Recently this car for sale was posted on the forum.
If you look at the engine bay photos you can see that the fuel line to the carbs and possibly the carbs themselves are lagged with insulation and aluminium foil. I wonder does this solution work?
Willo

[Richard Fridd]

How did the  assembled Lancisti sort the problem?

[willoroe]

A brave person sucked fuel through the airlocked line from the pump, once we had fuel flowing again there was no problem.
I've replaced the mechanical fuel pump with a new one since. The old one was worn and might have been a bit weak.

[Dave Gee]

Over the last few years I have been fighting this problem, and have done the following:
1)  heat reflective sleeve over the petrol pipe from petrol filter to carbs
2)  exhaust manifolds coated in zircon
3)  front exhaust pipes wrapped in exhaust tape
4)  electric fan with thermo switch in top hose plus an override switch under the dash
5)  return pipe from carbs to tank.

All this was done over 2-3 years and at the moment, touch wood, I haven't experienced a vapour lock. The return pipe was the last thing I did and that was approximately 3 years ago. Hope this is of help.

Dave

[GG]

Some years ago built a B24 engine with higher compression, a bit hotter cam, and Nardi kit. The heat in the engine bay got up there, and when sitting after running well, the heat would boil the gas out of the carbs. Part of this was due to the thinner phenolic spacers under the carbs (with the Nardi) so it would fit under the hood, about ⅛" thick instead of the normal ¼".

We ran a return line back to the gas tank, not from the back carburetor, but actually T-ed into the fuel feeding line - with like 3mm running to the carbs, and 1mm back to tank. That way, when the gas started percolating, the pressure build up would be relieved and the fuel would not overload the needle valves and flow into the engine.

Remarkably, it worked really well. On 90º days, you could do a healthy run, pull off, turn it off and it would start up like it was a nice cool engine. Never had any fuel problems since then. There was an elec Facets pump at the trunk (on a switch) pushing fuel to the mech'l pump at the engine, used largely for starting or sometimes for high speed runs, but was normally off.

[lancianut666]

return line seems to be the way to go

[Kaha]

Were do you connect the return line?
There are Filter Kings which have a connection for a return line, that would guarantee the correct preassure but it does not cool the fuel in the line to the carbs.
If connected to one of the banjo connector at the carbs, how do you size the hole for the return line? Too small and the flow will not be so high, to large will reduce the fuel preassure.
Are the ready made solutions for attatching a return line to the carb?

[Richard Fridd]

I have used a tee piece near to the carburettor connection  and a 0.5mm restrictor in the return pipe.


  Richard

[williamcorke]

I would find a few photos of people's return pipe installations very instructive.