Why does this happen while filling gas..?

Ever since I got my 40, every time I fill up with petrol I have to SLOOOWLY trickle the gas nosil so the gas goes down without bubbling up and kicking the safty fill. This happens on both sides. I takes forever to fill up wth a few gallons. I checked the vents and are clear. Atrhough I don't mind the extra attention, I want to fill and Go Go ! Does everybody have this problem?



John

I did and have improved it a little by adding an additional vent to each tank. I still have to pump fairly slowly but it doesn't click off much any more.

John, if you remove the small triangular cover plate from the panel just below the filler cap you will see that the tank breather pipe joins the main fill pipe a few inches below the top of the main fill pipe. If you are holding the end of the fuel delivery pipe above that joint you will be preventing air from being discharged from the tank as it is replaced by fuel, causing the "blow back" you are experiencing. Either try to push the filler hose further into the pipe to get below the breather, or better remove the tanks and install better controlled breathers . Frank

John,

My SPF has always had the same problem, anything more than dead slow will cause it to click off. I have found some station pumps are better than others and I try and use them, but I'll keep an eye on this thread for ideas.

Jim, the SPF needs better tank breathing all round, I understand the factory now do revised filler necks, Frank

Johngt40 said:

Ever since I got my 40, every time I fill up with petrol I have to SLOOOWLY trickle the gas nosil so the gas goes down without bubbling up and kicking the safty fill. This happens on both sides. I takes forever to fill up wth a few gallons. I checked the vents and are clear. Atrhough I don't mind the extra attention, I want to fill and Go Go ! Does everybody have this problem?



John

Click to expand...

John, it's because gasoline is quite volatile....meaning it easily atomizes and changes form from liquid to a gaseous vapor. I'm sure there's a more scientific description but that's basically it. As you pour it down the fuel filler at speed it easily bubbles. That's one reason why it's a good combustible for flowing through a carburetor or fuel injector in atomized form in the venturi/intake....and then combusting in the cylinder...

That, and your tank venting may not be very good, as was pointed out above.....

wealdenengineer said:

Jim, the SPF needs better tank breathing all round, I understand the factory now do revised filler necks, Frank

Click to expand...

Frank -- could you tell us SPF owner's more? What's different about the new ones?

I have an RF(1).
I found that not only trying to get the filler a little further in, but also turning the handle around until it faces away from me (both tanks), makes filling easy enough. Finding the "correct" angle takes a bit of trial and error but it is certainly achievable on my car.

Tim.

I suspect that simply jamming the filler in one-handed will never work. When filling my 427 Cobra, I use the motorcyclists technique--use one hand to operate the trigger on the pump, and the other hand to manually compress the rubber gaiter/spring affair on the handle. This tricks the pump into believing that the filler is jammed securely home, and fuel flows freely.

Of course you eliminate any proper automatic shutoff feature, so you need to keep your eyes on what you're doing or else you'll wind up with gas pouring out the top and all over your feet....BTDT! :laugh:

Mike - I tried that with my CAV and the result was gas pouring out the top of the filler even though I was watching for that to happen.

2124 said:

Mike - I tried that with my CAV and the result was gas pouring out the top of the filler even though I was watching for that to happen.

Click to expand...

I hate it when that happens....:furious:

YEAh - and it always seems to happen when there are at least 5 people standing over your shoulder asking questions about the car....

Whilst the breathers on our fuel tanks are not ideal, I think the issue also results from the foam/exploso safe fillings in the tanks. The fuel runs into this and backs up enough to trigger the fuel handle cut off or overflow out over the driver. If the tanks had an area where the fuel ran into a slightly bigger void just inside the tank it would then flow through the foam/exploso safe by having a larger surface area to be absorbed and so the back pressure (for want of a better description) will be reduced or avoided. This would also releive the fuel trying to go up the tank breather pipe too. I am building a 90 to 100 ltr fuel tank now for another car. This one will have the immediate void for the fuel to rush into giving a bigger surface area to dissipate from plus there will be two breather take off pipes, both in the back half of the tank to prevent them getting "blocked" by fuel trying to go into the tank. I guess bag tanks don't suffer this issue. My GTD suffers from this and I have learnt that if I fill up a bit more slowly with the pump nozzle nearly back out of the filler neck, the problem is greatly reduced and only takes a little longer than normal. I maybe have the pump nozzle half an inch into the filler neck. And I watch closely!!!! I did hear of one chap who used a broom handle to shove into the tank to push the foam/exploso safe filling back to create a void but to do this you will need to get access into the side pods of the car, a bit of a faff but perhaps worth doing if you are really suffering!

This is the Dax system - seems to work very well - I pump fuel at max flow
It will fill to about 7/8 tank without problem then the pump will click off

After that about 2 more squeezes of the pump fills to below the cap.

No foam in ank just explosafe wire wool stuff

Ian