What lets you run to lowest fuel level: up or down hill

[WarthogARJ]

I have 2004 Mk6 2.0 TD fwd.
Anyone know how the fuel tank suction is designed to drain the last bit of fuel: vehicle pointing up or down hill?
In most petrol cars i think you can get the last bit of fuel possible when pointed up hill.

But it’s a bit more complicated on a diesel because the ecu is designed to run rough when it detects a low level, so as not to run empty and thus get air in the system.
And the ecu is told that by the sender unit, which is just a float gauge.
Which will give different level readings depending on the angle of the tank.

So in effect the sender unit i calibrated to read correctly when the van/tank is flat and level.
And as it tilts up or down both the fuel level shifts, as well as how the float measures the level.

So i would think if Mr Ford Design Engineer was smart, he’d make things so fuel suction placement/fuel tank design plus the sender float orientation read like you had more fuel than you really have on level ground when you are going up hill.
Because for safety as well as getting to top of hill, you don’t want the ecu to start running on limp mode then.
And if this is the desig, then when you point downhill, your fuel system tells you have less fuel than you really have on level ground. Which is ok because if that low level triggers limp mode then at least you are going down a hill. Is safer to lose some power then

The design guy had a choice, because it is going to either read more or less fuel as it is headed uphill.
Because diesel is a liquid in a tank, and the suction is at one point.
And the sender level float is only correct when flat and level.

Anyone actually know?

I ask because my tank was indeed pretty low, but still reading >⅛. And am on a hill, pointing up, with front on ramps.
And my suction is not sucking any fuel up.
So it is either (another bad design by Mr Ford) or else my gauge is slightly out.
Which i can fix.

[scas]

the fuel sender unit is more towards the front of the tank , so if your vans pointing uphill it will read that is got less fuel in it

[WarthogARJ]

Ok thanks.
Very good observation.
And i think the suction is from the middle, so that will tend to miss out on fuel at the back if are pointed uphill.

Seems a poor design to me: would be better to be easier/safer to run and start while pointing up hill than down.

[bulls in transit]

How is having no power rolling backwards downhill safer than having no power rolling forwards downhill in a van?


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[Mike]

How is having no power rolling backwards downhill safer than having no power rolling forwards downhill in a van?

Check out who the op is

[Altransit]

How could allowing the van to run low on fuel, be a design flaw

Don't let it run low on fuel, and the problem is sorted

[richgold]

And my suction is not sucking

Dont you just hate it when your suction wont suck?

To be honest I'm quite liking these posts.

Its like having someone as mad as BJT, saying looney things like BJT does, but with a serious face and totally meaning it.

Its like some kind of reverse irony or post modern satire.

Long may it continue.

[WarthogARJ]

How is having no power rolling backwards downhill safer than having no power rolling forwards downhill in a van?

Check out who the op is

I didn’t say that.
Here’s the logic behind it that the engineers should follow.

We all know that running out of diesel is bad because it lets air in the system, which is hard to get out, especially on some models like Mk6.
So the ecu protects from that by making the engine run rough when it detects a low fuel value from the sender (which is just a float valve).
It is also obvious that losing power while trying to go up a hill (say for just another few hundred meters to reach top, and choose a spot to safely park) would be not only inconvenient, but a hassle, and quite likely dangerous.
It is equally obvious that running out of power, either via the ecu cutting back, or just no diesel whilst at high speed on the highway, say several lanes over, and perhaps in an area without safe stopping areas is unsafe.
It is also obvious from how the system is designed that the vehicle will “think” it is lower in fuel, relative to the reference position of flat and level, if it is on an angle: it could be designed so this was while going/parked uphill or going/parked downhill.
And sure, if you don’t fuel in, at some point you will run out.
But by good design you can make it less likely to happen when going uphill.

All those are very obvious, i trust nobody is confused about any?
Not even BJT?
No?

In the Mk6, and probably all other Transits, the suction is in the middle area of the tank, and the sender/float valve is in the front half.
So that has the effect of both sending a low fuel signal sooner when either going uphill or when you park uphill than when on the flat and level.
Note i said sooner
Yes?

Well, my point is that if you are going along and start to go up a short quite steep hill, you don’t want to all of a sudden lose power and stutter to a halt....and then have some other White Transit driven by another inmate ram into you when you suddenly slow down just as they revved higher to get up the hill.
Yes?

If instead you had a low fuel signal sent while going downhill, and the ecu cut back power, is not as big a deal. You don’t NEED as much power, Mr. Gravity is your friend. And the white Transit driven by BigJohnThomas who is tailgating you in a rush to get to church is less likely to run into you, because he has not had to rev up, but in fact ease off a bit.
Due to Mr. Gravity.

So in the next short while you manage to get down the hill and pull over, even in limp mode, both in a safer place, and without some tailgating idiot embedded in your rear.

Like if you are low in fuel, you WILL run out at some point. So you do want a warning. But you don’t want it to make things MORE dangerous.

It seems pretty obvious that having your ecu cut out whilst going uphill is a BAD idea.
In addition it would be best to pull fuel from the rear of the tank to enable this to work better too.

As far as parking, well if you don’t realize you are so low, and you do park facing uphill, and it won’t restart, well not even BigJohn can help you....is hard to get out of a tight spot by going backwards.

If you park facing downhill, well is also a hassle to not be able to start, but at least you could coast out using Mr. Gravity, and maybe BigJ’s wife to help push who you happen to have on speed-dial, and coast to bottom of the hill, where you then do have enough fuel to allow it to start and run maybe a few km to fuel. Or far enough to let you get towed (or given fuel) by RAC for free (they only tow if a distance from your residence).

So that is the design process that Ford should have gone through.

And sure you are not supposed to run out of fuel, but as they say sh*t happens, and fuel gauges can become faulty. And the point of good engineering is to design fail-safe if possible.

In a top notch engineering design company you have a Design Review Meeting where you put up the proposed design, and people go through it to look for stuff like this. I suspect Dearborn doesn’t have very well run Design Review Meetings.

[loot]

There must be a vacuum setup inside the tank because the sender is a clear foot away from the back and looking on eBay at the sender's they don't appear to have any straw tubes coming off them with weights on that you might expect to travel to the extremities of the tank, which in theory means that any slight hill would cause a problem.

The tank would need to be looked at internally to figure it out.
Maybe look in bemm.
There are 2 vents 1 on each end and no doubt a baffles inside.

I doubt that from empty and running to cutting out on an hill there will be more than a cup full of diesel in the tank remaining.(imo).

So I wouldn't be concerned really.
I'm sure that the tanks from 2000 to 2018 are very different at all, so that's a decent length of time for Ford's expensive engineering ppl to have figured it out

[ned]

My head hurts when my van develops a hic-up due to being low on fuel the gauge reads well into no mans land (on the flat ground) and I know I have about 10 - 15 miles of fuel before the van cuts out, plus when it does cut out there is still fuel in the tank

Yes I play fuel tank/gauge roulette N

[Mike]

To be honest I'm quite liking these posts.

Its like having someone as mad as BJT, saying looney things like BJT does, but with a serious face and totally meaning it.

Its like some kind of reverse irony or post modern satire.

Long may it continue.

He's an 'engineer' with too much time on his hands and a fvcking boring one at that. There are at least 3 Alan's here and two of them are idiots

[richgold]

I think I may have solved the original problem. After giving it lots of thought my solution is....

Put more fuel in the tank.

For step by step instructions on how to do this, refer to the owners manual.

Hope this helps.

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[Mike]

[Altransit]

I think I may have solved the original problem. After giving it lots of thought my solution is....

Put more fuel in the tank.

That is indeed a unique and ground breaking theory, who on earth would have thought of that

[Mike]

That is indeed a unique and ground breaking theory, who on earth would have thought of that

A real engineer?