Fuel Vaporisation

[Pyoor_Kate]

So, we're probably doing Pride again this year; and for those who don't know, last year Nikki had to (be) pull(ed) out due to fuel vaporisation, and the pump actually overheating and stopping entirely.

This year it's possible we'll have more standard cars along, and I'm wondering what temporary / instant fixes we can apply for people who don't want to mod their cars...

...suggestions?

[ColinP]

Kate,

I wonder if this could be used?
http://www.maplin.co.uk/module.aspx?ModuleNo=44554&doy=

It wouldn't be a raodside repair job, but I wonder if it could be adapted to cool the SU pump?

The other thought is a "wine cooler" like:
http://www.amazon.co.uk/exec/obidos/ASI ... 24-7382841
- put a couple into the freezer the night before, and keep in an isulated bag until needed?

You could always try the old mk 1 milk bottle cooler - a bit of mutton cloth wrapped around the pump/fuel line and pour water over it. the evaporative cooling should help.

I was looking at the Maplin stuff this summer, thinking about using a 12v fan (as used in a PC), along with a heat sensor/relay to turn it on and blowing over the fuel pump, but I didn't need it, so I put in on "hold"...

I think it should be simple enough to build a small baseboard system that clamps onto the pump, with a PC fan & temperature unit, powered from a handy 12 v connection.

Have fun,

Colin

[MikeNash]

I think a proper cure is going to need a space age solution like ColinP suggests.
With a thermocouple on the fuel line out of the pump and a pump stroke counter I found over the last two years that whenever the fuel temperature is over 21/23C vaporisation will occur. And in hot summer spell the fuel out of the petrol station probably is already, say, 15-18C. Not much to play with, and any in short stop in an ambient 25-30C its pumping away like mad.
I fitted a Mr Grumpy carb and pipe shield together with a tinfoil wrapping around the exhaust near the fuel pipe, but its no cure - not even sure its much improvement. What has helped I'm fairly sure is to feed the vaporisations back into the carb. I've Araldited a short piece of brake pipe into the airhole of the float chamber and into the back of the aircleaner (mine's a standard set up) and connected them with washer plastic pipe. Since vaporisation causes engine failure due to fuel starvation, this sort of compensates for it. And another great advantage when evaporating is far less pong in the cabin! Regards, MikeN.

[Matt]

Put some heat wrap around the manifold... its not good if you don't use the car much (because it will get damp and rot the manifold) but theres no reason why you couldn't take it straight off again!

[MikeNash]

Looks like only four of us interested in this problem, Kate!
When's the date of your next parade? (Can't be this year surely?)
We should bend our collective brains onto this - its the only true design fault on the car. There are other weaknesses, like the gearbox, but none as irritating as this. MikeN.

[bigginger]

The position of the Brake master cylinder! Why didn't they put it somewhere else when they gave up on the flat 4?

[Pyoor_Kate]

It's 2006 (the Parade) - but if we know we can 'cure' it then it means that we can happily accept allcomers to our float, wheras as it is we're a bit wary :-/

[rayofleamington]

The position of the Brake master cylinder! Why didn't they put it somewhere else when they gave up on the flat 4?

Yes - it only lasts 25 to 50+ years, quite terrible by modern standards!

As for fuel vapouristaion... The best solution is yet to be announced.... coming soon (early December) to a Minor you all know.

This will be thoroughly tested in Western Sahara... so best not to copy it until I'm singing my own praises (or wondering why I'd not seen the fatal flaw in the plan)

[bigginger]

Yes - it only lasts 25 to 50+ years, quite terrible by modern standards!

Odd that - they obviously don't on my cars, and they've all had to come out to be changed for disc brakes...

[Cam]

Install a rear mounted 'pusher' pump and it solves the fuel vapourisation problem!

It's not really a design fault as such as when the Minor was new the petrol did not evaporate so easily as it does nowadays thanks to the suppliers mucking about with it! I guess even Morris did not envisage petrol changing or their cars being used 40 odd years later!

[MikeNash]

Oh yes it is! Even when I was a lad and petrol was something you could wash your hands in, occasionally you got a stoppage on a hot day in traffic.
And the latest fuels just exacerbate a poor detail in the design, the closeness of the fuel pipe to the exhaust pipe. (Have we got a fueloligist on board to explain modern fuels?)
Re using the pump to push rather than pull, where do you put your pump? I don't like the idea of it under the car and exposed to water. And I'd like a bit of a desciption of cutting the fuel pipe and the couplings used before I have a go. I don't like being a pioneer!
But for Kate, who I supppose wants a mod that's very easy to install on cars that will just be there for the day, we're probably restricted to stuffing in some insulation in the appropriate places. MikeN.

[ColinP]

Mike,

The mini had a "pusher" SU fuel pump in the nearside rear wheel arch

That gather all the mud, grit etc. (which is why some people recommend hitting the kerb with the mini - just to keep the points working!).

From the information I got earlier this year regarding the vapour pressure of petrol, it seems as if there's only a small change needed - the system works quite well until hot summer days.

I wonder if the pump could be moved downwards about 15 inches to where the fuel pipe enters the engine bay? That would reduce the height that the pump has to suck the fuel, which would reduce the vapourisation before the pump. Alos allows the pump to be in a cooler part of the engine compartment (but possibly nearer the exhaust).

A length of flexible hose (like the heater air intake) could add airflow, but the problem is usually when the car is stationary - so it would need a fan to keep it going.

I don't know about the mounting of this, though I guess it's easy enough to use a bit of Dexion. The other question is whether the standard SU has sufficient push to keep the float chamber supplied.

As a fix to a problem, I really like the wine cooler one - if you don't need it to cool the pump, then you can cool the wine!

Colin

[Willie]

Has anyone done a definitive test on wether the problem lies in the fuel pipe
before the pump,the pump itself,or the pipe to the float chamber?? If it is the
pump itself then it will be no good changing to a rear mounted' pusher' type
as the pipes will still be in the original positions in the engine compartment.
Surely it would be a fairly simple job to extend the fuel supply pipe along the
chassis leg so that it fed the repositioned pump which would now be near the
front of the engine mounted on the inner wing.
MIKE.....most of the cars I have mucked about with have had bits of flexible
pipe in the fuel lines without any problems, you could use the normal 'pump to carb.' one on the Minor.

[ColinP]

Willie,

The data from the fuel standards gives three grades (vapour pressure):
measured at 100F = 38.8C

Summer Range 45.0 - 70.0 (2) (kPa)BS 2000: Part 394 6 – 11 psi
Winter Range 70.0 - 100.0 (2) 11 – 14.5psi
Intermediate Range 45.0 - 100.0 (2) 6 – 14.5 ps

The SU pump is rated at 6psi "suck", so it's clear that on a hot day the maximum sudden suck of the pump can reach the vapour pressure of the fuel. Obviously, that's worst case, but if the fuel lines are restricted/filters partially blocked etc that isn't going to help.... and the pump is intermittant not continuous, so there's surges in the system.

And it doesn't need to reach the actual vapour pressure to have a significant amount of vapour - not liquid. Once that happens, my SU pump works harder, gets hotter, and then the whole thing gets worse.

It's interesting to note that there are 3 grades of fuel (summer/winter/intermediate). Also, most cars these days seem to have pressurised fuel tanks.

Colin

[rayofleamington]

Install a rear mounted 'pusher' pump and it solves the fuel vapourisation problem!

I have wondered about that, but as my car will be going off road and through the desert too, I didn't want it underneath, and any damage to the fuel pipe downstream of the pump (due to stones / grounding etc..)could cause a major fuel loss! This would require an internal fuel pipe to limit the risk and it starts to turn into a major excercise.

[Multiphonikks]

I think we'll have to get some exhaust wrap too. Kate and I had a chat about that the other day

Of course, Carrie can't have any - but we think she'll be okay. I think also part of the plan will have to be where we're placed in the parade (I'm going to try and get us near to the front)

Nikki

[Cam]

Oh yes it is! Even when I was a lad and petrol was something you could wash your hands in, occasionally you got a stoppage on a hot day in traffic.
And the latest fuels just exacerbate a poor detail in the design, the closeness of the fuel pipe to the exhaust pipe. (Have we got a fueloligist on board to explain modern fuels?)

Mike, like you say, you OCCASIONALLY got stoppage on a hot day, but nowhere near as much as today. If it was as bad back then as today then it would have been re-designed. My mum's old 1957 Minor (back in the late 60s) never suffered with it.

Re using the pump to push rather than pull, where do you put your pump? I don't like the idea of it under the car and exposed to water. And I'd like a bit of a desciption of cutting the fuel pipe and the couplings used before I have a go. I don't like being a pioneer!

Well, you don't use the standard pump, but get a sealed electronic version (like my FACET pump). It pressurises the fuel to 5psi and then I have a filter and regulator (where the old pump was positioned) which drops it just below 2psi for the carb. No problems at all. Pressure increases the temperature at which the fuel vapourises and since modern cars run pressurised fuel lines they don't have the problem. So, if you want to cure the problem properly then pressurise the line! Trouble is though that this prevents originality.

I have mounted the pump under the boot floor, in-between the diff bump and the tank. I cut the original copper line and used a braided link pipe to go from the copper line to the pump and then used braided fuel hose to go into the engine bay and up to the regulator.

But for Kate, who I supppose wants a mod that's very easy to install on cars that will just be there for the day, we're probably restricted to stuffing in some insulation in the appropriate places. MikeN.

Probably, yes, but the place that causes the problem is the copper line that pokes into the engine bay low down and finishes at the pump. The outlet of the pump is fine as it's pressurised. The sucking effect on the fuel line slightly depressurises the fuel which aggrivates the problem, expecially the section being heated up next to the manifold.

[KirstMin]

When do we get to see some action photos of you and Carrie?

[Multiphonikks]

When do we get to see some action photos of you and Carrie?

Erm... when I finally get around to borrowing my friend John and his 'nummy' camera
N

[Pyoor_Kate]

You could just use mine, or is my 70 quid digital 'not good enough for Carrie'? ;-p