Ran out of fuel and now missing and Backfiring :(

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Aidan
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Re: Ran out of fuel and now missing and Backfiring :(

Post by Aidan »

feed pipe comes from the centre of the tank where there is a baffled sump so most of the crud in the tank doesn't come in to play - certainly the case on a fuel injection tank which also has a nylon strainer to protect the pump but I think even the carb and diesel tanks have the sump, at least on the genuine tank maybe not on the cheapest aftermarket ones

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Re: Ran out of fuel and now missing and Backfiring :(

Post by ghost123uk »

Aidan wrote:feed pipe comes from the centre of the tank where there is a baffled sump so most of the crud in the tank doesn't come in to play
I don't understand :oops:

Hi Aidan by the way :ok
Got a new van, but it's a 165bhp T4 [shock horror] Accurate LPG Station map here

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Re: Ran out of fuel and now missing and Backfiring :(

Post by melvin »

ghost123uk wrote:OK folks, can I throw this into the conversation.
I have often thought that so many folks get this wrong, but maybe I'm missing something ->


The open end of the feed pipe in the tank sits very close to the lowest part of the tank doesn't it (obviously).
Now, consider the van has say 4 gallons of fuel in it, and it has been stood for a week, any sediment etc will have sunk to the bottom of the tank.
On starting it up, the pipe sucks and any muck is sucked up and gets caught in either the tank gauze filter, or the main fuel filter.

Now consider a situation were the van is driving along and there is barely any fuel left and it, then it runs out.

What's the difference?

It doesn't matter whether there is 4 gallons or just 1/2 a pint, the sediment is always going to be concentrated at the bottom, were the feed pipe is, surely.

This has always been my thought on running the tank low/dry, but on inspection of the carbs I had rusty deposits in the float bowl, not sure how they could have gotten there as the fuel filter is only a month or so old! Anyway, split the carb removed the jets and blow every orifice through, chucked it all back together and it sill ran rubbish, stood there looking at it for a few minutes, pulled off the wires going to the fuel cut off and put them back on, reved it up a bit and then suddenly it cleared! So not too sure whats happened but I have noticed the following.....

If I pull off the Fuel cut off valve wire on the left carb the engine stalls, if I pull off the wire going to the right hand fuel cut-off the engine still runs, should this be the case? I've presuming not! Both valves click when the wire is connected though.

Also with 2 gallons of fuel in the tank if I pull off the fuel pipe from the tank should fuel pour out? Mine did not, but when I removed the filler cap fuel and tried again fuel came out?

and before it gets mentioned again, I'm going to sort out the fuel gauge as my next job :oops: , along with a good inspection of the tank and possibly replacement.

Melvin

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Aidan
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Re: Ran out of fuel and now missing and Backfiring :(

Post by Aidan »

ghost123uk wrote:
Aidan wrote:feed pipe comes from the centre of the tank where there is a baffled sump so most of the crud in the tank doesn't come in to play
I don't understand :oops:


https://www.thesamba.com/vw/forum/viewt ... p?t=630469

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Re: Ran out of fuel and now missing and Backfiring :(

Post by tobydog »

ghost123uk wrote:OK folks, can I throw this into the conversation.
I have often thought that so many folks get this wrong, but maybe I'm missing something ->


The open end of the feed pipe in the tank sits very close to the lowest part of the tank doesn't it (obviously).
Now, consider the van has say 4 gallons of fuel in it, and it has been stood for a week, any sediment etc will have sunk to the bottom of the tank.
On starting it up, the pipe sucks and any muck is sucked up and gets caught in either the tank gauze filter, or the main fuel filter.

Now consider a situation were the van is driving along and there is barely any fuel left and it, then it runs out.

What's the difference?

It doesn't matter whether there is 4 gallons or just 1/2 a pint, the sediment is always going to be concentrated at the bottom, were the feed pipe is, surely.

I used to think that also.

Imagine a bucket full of water with some gravel in the bottom and you shake/swirl it around, then with just enough water to cover the gravel. The water can slosh around more and pick the gravel up when the level is very low?
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Re: Ran out of fuel and now missing and Backfiring :(

Post by CovKid »

A strong earth magnet stuck to underside of tank and away from centre helps to trap any fine rust.
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Re: Ran out of fuel and now missing and Backfiring :(

Post by NicBeeee »

CovKid wrote:A strong earth magnet stuck to underside of tank and away from centre helps to trap any fine rust.
Isn't rust not magnetic?

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Re: Ran out of fuel and now missing and Backfiring :(

Post by ghost123uk »

Rust is magnetic.
Got a new van, but it's a 165bhp T4 [shock horror] Accurate LPG Station map here

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Re: Ran out of fuel and now missing and Backfiring :(

Post by NicBeeee »

ghost123uk wrote:Rust is magnetic.
Oh no it isnt

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Re: Ran out of fuel and now missing and Backfiring :(

Post by ghost123uk »

Well, all the Ferric Oxide (brown type) cassette and R2R tapes must be just a myth :roll: :wink:
Got a new van, but it's a 165bhp T4 [shock horror] Accurate LPG Station map here

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Re: Ran out of fuel and now missing and Backfiring :(

Post by NicBeeee »

ghost123uk wrote:Well, all the Ferric Oxide (brown type) cassette and R2R tapes must be just a myth :roll: :wink:
Ah I see we're you are going wrong, ferric oxide isn't rust. Iron oxide is.

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Re: Ran out of fuel and now missing and Backfiring :(

Post by chris7ian »

The last time I ran out of fuel in my bus it created a vapour lock/vacuum in the fuel system and ran like "pooh" - I cured it easily enough once i'd figured out what was going on by starting the engine with the the fuel filler in the quarter panel open and running it for a short while (to the petrol station at the opposite end of the street!)
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Re: Ran out of fuel and now missing and Backfiring :(

Post by melvin »

Hi All,
Just to wrap up my problem, as you see so many open ended posts on here.
Bought a new fuel tank and replaced all rubber breather hoses, glad I did as they were quite perished at the ends and the rubber inlet gasket was 70% self-amalgamating tape!
Found the fuel sender problem to be a split hose inside the tank causing the fuel to draw from near the outlet as opposed to the centre of the tank so that's all sorted.
The missing and backfiring was caused by a bit of crud caught in the fuel cut off valve causing one side to run lean as the valve didn't open properly, tested this on the bench with the valve connected to a car battery and connected a piece of hose to the end of the valve, blew down the hose and applied 12v, one valve let air through and the other did not. A good blast of air freed the blockage and bingo she is now purring like a kitten.
Still have my slight misfire, but I'm sure I'll cure that soon, about to balance the carbs and fettle them a bit to see if that makes a difference, but other than that I'm well happy to be back on the road, thanks everyone for your replies and help, much appreciated!

Cheers
Melvin

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