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Fuel Vaporisation in hot weather


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Hi Chris

Others shall no doubt have other thoughts... I’ve encountered the problem a couple of times when fuel level in the tank was around ¼ or less... As soon as I filled up all was fine... I’ve also heard that darker cars suffer more due to heat absorption and transfer to the tank temperature... 

Hope this helps.

Cheers

Ian

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The fuel that refineries supply to the market is adjusted for the ambient conditions. There is summer and winter grade fuel. So if you buy fuel in SA, it may have a slightly higher boiling point.

Regards,

Waldi

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It would interesting to know what system you have,

Lucas pump or Bosch?

Which PRV are you using, existing or diaphragm?

What filter are you using CAV  or inline filter?

How many return lines are there in the top of the fuel take, one or two? 

I have found that its important if you are using the CAV filter that it is a genuine one from Landrover, not the lookalike ones.

I have a CAV filter setup with a Bosch pump and want to change the PRV return into a new second return line in the top of the tank.

John

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John L. 

We have Bosch pump mounted in wheel arch with 2 returns to fuel tank. 

We have an in line motoquip filter. 

I think this is the PRV (picture below) 

We have rubber hoses ( possibly need replacing to reduce petrol smell?) 

we are contemplating wrapping the alloy tank in some kind of reflective (gold) sheets to reflect heat  

 

 

 

7D5AEB59-F431-489A-8D09-240E5F691642.jpeg

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Hi Chris,

Wrapping the tank will make things worse, you need cooling fins on the tank:) once the fuel temperature is higher than the boot temperature. The heat which rises the fuel temperaturr is created by energy dissipation from the Bosch pump. Unless it is very hot in the boot, which could well be in SA. A bag of frozen peas or ice comes to mind.

I assume you have an inlet filter, it looks pretty small. I would increase the size, also from the hoses from tank to pump.

There are many posts on this forum on (Bosch) fuel pump issues, do a search via Google. Also about permeability from fuel hoses that are not suitable for ethanol containing fuel.

Cheers,

Waldi

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Although I have now sold my car one Option I was considering with my car also retaining the Lucas Pump was a Fuel Cooler as fitted to most modern Diesel cars?

I was always amazed how hot the pump got, on one of the hottest days of the summer a couple of years ago I could hardly touch the pump after returning from a Triumph show at Santa Pod raceway, although I never let the tank drop below a Quarter full  

Have a look on E-Bay, the one I was considering plumbing into my fuel system was for an X-Type Diesel Jag I seem to remember.

Regards

Gary

 

 

Edited by Gary Flinn
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Another option I was considering to fit over the Pump was something like the Heat sink & Fan here used on Model Race Cars, although I struggled to find one the correct diameter for the Lucas Pump?

(I did fit a heat sink designed to cool a Training Bike motor but it didn't work well:wub:)  

Modelsport hw86080130 Heat Sink & Fan.jpg

Edited by Gary Flinn
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Chris

Are you actually currently having problems with vaporisation, or is this a precaution for the SA trip?

I think the system you have now is probably about the best you could get, I think also you might benefit from a larger inlet filter, and perhaps a larger fitting in the bottom of the tank, see a previous forum article.

John

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Hi I think much of the heat cones from a hot engine.

That metering unit gets too hot to touch and sends unused hot fuel back to the tank.

My 6 copes well in high temperatures as long as the road speed is high, if stopped in traffic for more than a few minutes with 25% fuel or less the pump gets louder. 

An immidiate fix is to add fresh fuel, I keep a can as even a gallon of cool fuel helps until a petrol station can be found.

A more permanent fix would to add a fuel cooler as mentioned earlier or, for your trip, adding an electric fan to keep the engine temperature down. 

Laurence. 

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I often run the bonnet just un latched, on the safety,  it certainly helps with the air flow.

I don't think there is much fuel return from the MU, its the PRV that is heating the fuel, would be interesting to know if the Diaphragm type is better at not heating the fuel.

John

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On 6/26/2019 at 3:03 PM, Chris Ham said:

Hi, we are taking our TR6 on an Endurance Rally to South Africa in October this year where temp will be mid 30's, We are concerned about fuel vaporization and fuel pump performance. Has anyone resolved what appears to be a long standing problem? 

Chris H

Chris,

We have just returned from a 3 week/3,000 mile tour in Europe visiting Spain, the South of France, Italy and Switzerland we got caught in some horrendous stop-start traffic on the drive from the SofF to Italy with temperatures hitting 36-38C.  For most parts of the driving the weather was between 28 - 34C. My TR6 runs a Bosch pump and diaphragm PRV and I didn't experience any problems with fuel vapourisation or have any injection issues, I did keep the fuel tank topped up when whenever possible as the cold fuel helps keep the system cool. Quality of fuel also helped, I avoided 95/98 (E10) like the plague as I found the car did experience pre-ignition on E10, but no such problems with 95/E5.

Hope the above is useful.

 

Regards, Andrew

Edited by Andrew Smith
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55 minutes ago, John L said:

 

I don't think there is much fuel return from the MU, its the PRV that is heating the fuel, would be interesting to know if the Diaphragm type is better at not heating the fuel.

John

Hi John,

the heating of the fuel is caused by the pump: the higher the electric current, the warmer the fuel gets. It is not related to the type of PRV.

Bosch pumps do / may solve some issues with the original Lucas pump (but opinions differ amongst the forum users), but due to the higher flow-rate and related energy consumption of a Bosch pump, they increase the risk of:

1) Cavitation in the suction line due to reduced pump inlet pressure.

2) Scattering of the original PRV

3) Increased fuel temperature, which magnifies item 1 above.

4) Lower voltage at the pump due to higher current draw.

5) Higher load on the ignition switch, if the original wiring is not modified.

The issue with the Bosch pumps is that there are only a limited number of types suitable to deliver 105 psi, and all of these have a much higher flow rate than the original Lucas pump.

FWIW: I have a Bosch pump.

Regards,

Waldi

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Just to add that a Bosch pump fitted outside of the boot in the rear wheel / wing area where it gets lots of cool air seems to work well

i’ve had this on two cars now, both of which would run cleanly right down to the two dots at empty on the fuel gauge !

Steve

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