Hello im wondering if anybody can help me with a niggling problem with my 2005 1.3 multijet.The van runs perfectly when it has lots of fuel in it but when it gets down to about half a tank or a bit below it will just cut out randomly and then will not restart for atleast 20 minutes.I have also noticed that it only does this when i have taken my foot off the accelarator??any help would be much appreciated.

Hi, is the vehicle a conversion?

How do you mean? Fuel conversion? or engine size? I don't think so either way as the log book matches up perfectly and the chasy and vim numbers are correct,the van has only done 86,000 miles, there is a reciept In the history for over £900 where the van has been doing the same thing,but I have discovered it only suffers this problem when fuel is halfway or less,very strange!

I may be way off whack but do you get a loud hiss when you take off the fuel filler cap ?

It's possible that the breather hole in the cap is blocked and you are getting a vacuum.

If so it's a cheap cure, either open out the hole slightly or replace cap.

If that works, Ill be amazed something so simple can solve a big problem!

I can't say that I have heard a loud hissing when opening the filler cap to be honest and I never let it get below half a tank anymore because its just a pain and embarrassment just cutting out in rush hour traffic!Due to the nature of the fault I would assume that it's a fuel flow problem? I have been told there are 2 fuel pumps? One in the engine and a second pump in the tank it's self! Seeing as the van only cuts out when the pump is not under load would indicate that there is a fault with the 2nd pump??

spjonesuk said:

If that works, Ill be amazed something so simple can solve a big problem!

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Yes it can. A blocked cap can cause the tank to collapse due to the vacuum inside it, used to be a big problem in the 70s-80s.

The reason the conversion question was asked is that if the original van has been converted for special use, e.g. rear wheelchair access with lowered floor, the tank may be a reduced size. Often the converter will use the original gauge sender, in a smaller tank, which will lie. When it cuts out, once restarted, fill immediately and see how much it takes. This will tell you how much is actually left in the tank when it stops.

Ok,but how is that going to help?

Also what do you mean by cause the tank to collapse?

slapshotpro said:

Also what do you mean by cause the tank to collapse?

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It's a Vacuum..!!, the opposite of pressure..!!

As the fuel is used, air needs to enter to fill the space. If the air cannot enter, the tank will squash inwards, pushed by atmospheric pressure outside with a vacuum inside. This makes the tank smaller and can prevent the sender unit dropping, so the sender says half-full when the tank is empty.
Grovel under the car and look at the tank.
If the tank is squashed you need a new one, and to fix the breather problem.
If you've got a converted van, with a smaller tank, you may have to get used to the reduced range.
If all seems ok, you could have a faulty sensor, reading half-full when actually empty, so filling the tank will tell you how much you've put in. Compare this with the capacity in the handbook to know how much was still inside. This will tell you if it was empty, or a fuel supply problem.
Fill it to the brim. Note the mileage. Run until the problem occurs. Refill, record the fuel used. Note mileage again and compare. This will tell you how far you've travelled on how much fuel and will help identify whether you have a lying sender, a reduced capacity tank, or a fuel supply issue.

Good explanation if he don't get it now, there's no hope!
Luigi

Without meaning to stray off topic to far, please can anybody confirm if the sender pump in the fuel tank pushes fuel up constantly when the ignition is or only at initial start up. If it is only at initial start up to prime the main pressure fuel pump with fuel, is there a time sensitive relay somewhere that acts as an off/on switch?

It pushes all the time.
When you first turn on the ignition it should push briefly to ensure fuel is available at the high pressure pump at the front. It should then push again during engine cranking, to maintain the supply. Once the engine is running, it should continue to push. If oil pressure drops, putting the oil light on, or if the engine stalls, it should stop as a safety feature to prevent fuel being pumped out in the event of a collision, or other breakdown.

The pump at the front takes the supplied fuel and pressurises it for injection into the cylinders. This pump does not suck fuel from the tank, just squeezes what its been given.

With a petrol engine, the pump at the tank does the whole job, supplying fuel at a pressure to inject into manifold or cylinder. Petrol injection is at a significantly lower pressure.

portland_bill said:

It pushes all the time.
When you first turn on the ignition it should push briefly to ensure fuel is available at the high pressure pump at the front. It should then push again during engine cranking, to maintain the supply. Once the engine is running, it should continue to push. If oil pressure drops, putting the oil light on, or if the engine stalls, it should stop as a safety feature to prevent fuel being pumped out in the event of a collision, or other breakdown.

The pump at the front takes the supplied fuel and pressurises it for injection into the cylinders. This pump does not suck fuel from the tank, just squeezes what its been given.

With a petrol engine, the pump at the tank does the whole job, supplying fuel at a pressure to inject into manifold or cylinder. Petrol injection is at a significantly lower pressure.

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Thanks for reply Portland Bill - part of my interest in finding out how the fuel feed system works is prompted by a problem I've got with my 1.9JTD diesel. I can't get an electric feed to the lift tank pump for some reason. Every connector I've tried doesn't register a current feed on my multimeter and small 7.5amp fuse seems OK. Even tried swapping relays for similar type but made to difference. Tried the fuel cut off switch and no current feeding the switch. Changed the crank sensor, cleaned out and freed off the EGR valve. Renewed the glow plugs and am going to change the cam sensor. Weird thing is if I hand prime the main pressure pump the car will start on the key and happily run until I turn the key off. After initial system check, the immobiliser light goes off so I've assumed that is OK.
If the main pressure pump does not suck fuel up from the tank, that says to me that the fault is rectifying itself when the car is running because something as got to be fueling the main pressure pump.
If I can't get this sorted, I thinking of possibly introducing a switched fused live switch to the lift pump and see if that works.
Apologies for semi ambush on thread, but it some respects, this post is relative.

Main pump in tank will only get a feed at first ign on, when cranking, or with engine running with good oil pressure. Before ECUs this was controlled by relay and oil pressure switch. I think now ECU controls it all, possibly by switching its earth, so in that case would have a feed all the time ign was on. See if you can find a wiring diagram, somewhere on here hopefully - can anyone point us to one?

udtrev said:

I may be way off whack but do you get a loud hiss when you take off the fuel filler cap ?

It's possible that the breather hole in the cap is blocked and you are getting a vacuum.

If so it's a cheap cure, either open out the hole slightly or replace cap.

Click to expand...

Mine has always made that noise (just filled up today and noticed it again).
In fact, I can't remember a vehicle where there hasn't been a noise as the seal is broken on the fuel cap.

2668GRIFFIN said:

Good explanation if he don't get it now, there's no hope!
Luigi

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I suspect it was a ploy to get their 5 posts = necessary to post pics / place an ad..

Tanks are supposed to run slight negative pressure, better in an accident.

Nowadays, there's usually a valve inside the cap that allows air in to maintain that slight negative pressure. If this gets blocked, or otherwise fails to function properly, it can lead to a vacuum in the tank. This can stop the fuel flowing, and in some cases. cause the sides of the tank to collapse. The intake of air is then quite a gasp, rather than the usual hiss.

Many of you already know this, of course, but for those who didn't, hopefully this will help.