Where does all the fuel go

vwtrev1 Slammed & Awesome Dubber

81 posts · joined Mar 2005 · 17 Oct 2006, 4:05 pm

#545416

My van has an electrical fuel pump and is a 2litre twin carby model.
First question why was the van most likely changed to an electrical fuel pump is the standard mechanical pump unreliable.
Second question when I turn off the key leave overnight the next morning you nneed to wait for the clicking of the pump to finish before starting. Sounds like it is filling up the carbys where has all the fuel gone overnight.

Trevor//

bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 · 17 Oct 2006, 4:45 pm

#545426

I'm not highly experienced at vans, but offroad wise, from a few books i was reading, it is sometimes actually better to have a standard fuel pump. Cause if u have an electrical problem, then ur electric pump ain't gonna work... (IE: wire shorting somewhere, or the pump dead.... the standard ones seem to have greater life) While, if u have an electrical fault along the way... the fuel pump will still keep going (with the engine)

The clicking before starting... tis same as a commodore... it is just pumping in fuel...

where does it go overnight? well... spose it could be a few things....

This is my guess....
Cause u have an electric fuel pump... as soon as u stop the engine (with the key), the pump switches off... but ur engine was just idling at a few hundred or wateva rpm as soon as u turned it off. The engine requires a few split seconds to loose momentum, and finally come to a hault.... so as soon as u turn the key off, there will be that second or 2 delay before the engine stops turning (due to momentum... then it finally stops). Cause ur fuel pump stops instantaneously, and the engine doesn't, the engine just spits the remaining unburnt fuel vapour into the exhaust and takes a few gasps of plain air... (IE: NO FUEL comes in while the engine slows down cause the electric fuel pump has cut off the fuel line by being turned off)

thats one possibility... the other is... fuel only explodes as a vapour... if u leave it over night... the atomised fuel that comes from the carby (the vapour, mix of fuel and air) settles into a hardly explosive (in comparison) liquid residue. And therfore in the next morning... ur engine requires ur pump to do a few clicks to refresh it with some vapourised petrol.... However though, the residue is able to evaporate over night into the air inside the combustion chamber, making it explosive... hardly as much as say what a carby and fuel pump would be putting in though.

Hopefully that might shed some light... lol
just some educated guesses.

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Volkswagenboy Staggers Automotive.

2,437 posts · joined Jul 2005 · 17 Oct 2006, 6:19 pm

#545475

How long does it take to pump up? One reason could be the fact that your pump is pressurising the fuel lines into your carbies and into your float chamber/bowl, then once you turn the ignition off the fuel pressure equalises on either sides of the pump.
Do yur carbies actually 'empty'?

And as to your electric pump question, there's a numer of reasons as to why the pump was changed:
*Diaphram in old pump wore out.
*Someone just liked the idea of an electric fuel pump.
*Reliability.
Anything really.
Electric and mechanical both have their pros and cons.

Have you checked your carbs for any external leaks, which could even cause the fuel to run back?

-Staggers.

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68AutoBug Beetle Restorer - Experience over 138\% - YIKES --

11,654 posts · joined Aug 2002 · 17 Oct 2006, 7:02 pm

#545494

I'm an electric fuel pump fan...
and have one fitted to My beetle...
it usually ticks two three times when its turned on...
with it turned off, the Beetle can go about 100 metres or so... before running out of fuel...

I believe its just pressurising the fuel system when it starts ticking...
Other Beetles i've added electric fuel pumps to, all do the same thing...
Some tick five or six times when they are switched on...
seems to depend on the pump and fuel pressure regulator

maybe they do add a bit of fuel into the carby fuel bowl..
when switched on...

but I'm sure no fuel is lost...

Lee

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Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 · 17 Oct 2006, 8:08 pm

#545553

its normal for an elec pump to run abit when u turn the ign on to fill the fuel bowls up
just depends how long its running for
if its only a few secs that normal
there will always be abit of evaporation specially when a motor is shut off hot but its very minumal
i've pulled arpt carbs that have sat for a fortnight that still have a full bowl
given the placement of the standard 2L pump and also the cost i;m not surprised its been replaced with an electric one
they work well aslong as they have a saftey cut off if the engine stalls
ie. wired to oil pressure/ charge warning lights

-Joel

greedy53 Bishop of Volkswagenism

3,062 posts · joined Mar 2006 · 17 Oct 2006, 8:08 pm

#545554

i use a one way inline valve on the fuel line keeps fuel bowl full and no run back mine was about afoot from the carby

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helbus Administrator Mad fabricator, paint and body

7,386 posts · joined Sep 2002 · 17 Oct 2006, 11:46 pm

#545750

Important thing with an electric fuel pump is to have a safety switch so that the pump will not operate unless the engine is turning over. For example the safety swith senses a pulse from the coil when cranking or when the engine is running. The fuel pump operates. When the engine is not turning, the pump will not operate.

Why? It is an unfortunate situation when a fuel line bursts and the pump continues to feed an ignited fire when the engine has stopped. A rollover or large crash could cause this. If you were unable to turn the ignition off for some reason, it may be as simple as you being inside while letting the vehicle idle away for a minute, and in that time the fuel is continually spraying on a fire in the engine bay.

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