Fuel tank issues

[wild_one]

My car seems to run out of fuel when the gauge is still showing 1/4 full. The gauge cluster passes the self test thing. It works correctly in every other way. I'm guessing either faulty sender or pickup. Does anyone have any experience of diagnosing the sender. Or, the process of removing it which appears to involve removing the fuel tank or cutting a hole under the back seat?

[Tdci-Peter]

6 hours ago, wild_one said:

My car seems to run out of fuel when the gauge is still showing 1/4 full.

Just to check, is it really running out of fuel, or just having some odd symptoms? Once a 1.8TDCI gets air into its fuel lines, it will usually not restart without priming. Which means disconnecting fuel lines and using a pump or priming bulb.

It is possible there is a slight leak in a fuel pipe or the filter housing. This could let just a trace of air in, which will increase as the tank level drops. Then the engine may hesitate or stall. If the bubbles are small enough, it will restart with a bit of cranking. But lines full of air due to an empty tank will be a permanent stop until primed. You will not see leaks, no fuel will come out unless maybe the car is parked nose down on a very steep hill. But air can be drawn in as the system up to the main engine pump is normally under suction.

Another test is to measure how much fuel you can get in the tank. If really empty, then it should be about 53litres.

If you can get 53l in when showing tank 1/4 full, then the sender is the likely fault. I looked at the hole under the seat method, it looked to be a much easier option than dropping the tank, especially without garage style lifts to get the car high enough. But there was no need for me to try it, as I found that despite Haynes, there was no pump in the tank on these. And that is what I was trying to check.

BTW My gauge is very inaccurate. When it read a tiny bit over 1/2 full, I could only get 14.3l in, or about 27% of a full tank. And there is about 12l left in when it reads empty.

 

[wild_one]

21 hours ago, Tdci-Peter said:

Just to check, is it really running out of fuel, or just having some odd symptoms? Once a 1.8TDCI gets air into its fuel lines, it will usually not restart without priming. Which means disconnecting fuel lines and using a pump or priming bulb.

It is possible there is a slight leak in a fuel pipe or the filter housing. This could let just a trace of air in, which will increase as the tank level drops. Then the engine may hesitate or stall. If the bubbles are small enough, it will restart with a bit of cranking. But lines full of air due to an empty tank will be a permanent stop until primed. You will not see leaks, no fuel will come out unless maybe the car is parked nose down on a very steep hill. But air can be drawn in as the system up to the main engine pump is normally under suction.

Another test is to measure how much fuel you can get in the tank. If really empty, then it should be about 53litres.

If you can get 53l in when showing tank 1/4 full, then the sender is the likely fault. I looked at the hole under the seat method, it looked to be a much easier option than dropping the tank, especially without garage style lifts to get the car high enough. But there was no need for me to try it, as I found that despite Haynes, there was no pump in the tank on these. And that is what I was trying to check.

BTW My gauge is very inaccurate. When it read a tiny bit over 1/2 full, I could only get 14.3l in, or about 27% of a full tank. And there is about 12l left in when it reads empty.

 

It runs fine in all respects other than that I treat 1/4 as empty, although in reality it's probably a little under 1/4. I only found out about this issue after letting it run down to 1/4 once, as i usually top up below 1/2 a tank. The car failed to start and after a comprehensive check of the engine and pipework, a gallon of diesel and she eventually fired up (without any 'priming' issues) and has run faultlessly for the last few weeks. When the gauge is showing 1/4 £35 will fill it up.

[silvercanary]

is your filler neck rusty? 

it could be depositing rust which is blocking the in tank fuel strainer? if you can't replace the filler pipe you have to periodically take the strainer out (if there is one) and clean it off and filter your fuel at the same time for bonus miles (syphon into a large plastic box, let it sit a few mins then don't tip it all back in, works well). that's sometimes the case on the mk1 anyway.

if your filler pipe is plastic you can rule out the rust problem i expect. i had a seized pump on my petrol mk1 but it sat for 3 years first. and then i freed off the pump and it works fine still after 19 years. and if you've no access hole you've got to drop the tank or very carefully cut an access hole. i say carefully so you don't slice through the fuel pipes with an angle grinder like i nearly did. the hole is very handy though unless you have a proper ramp. even then it's useful however. 

it could be a faulty pump (i think some diesels have one in tank, some don't) but idk about mk2 diesels well enough to say and if the pump is now faulty it could have been caused by something else. either excess load caused by filter/strainer blockage either upstream or downstream or running with low fuel has caused it to run too hot for too long.

and there's never an empty tank when it reads empty. it should go below the red line a bit though don't risk your life trying...

[Tdci-Peter]

2 hours ago, wild_one said:

When the gauge is showing 1/4 £35 will fill it up.

£35 is only 28 litres at supermarket prices, a lot less at BP premium prices! So the tank is nearer half full. Seems like your gauge is reading not so far off mine, which is well above the actual tank content.

The symptoms do sound like a bit of air ingress to me. The fuel filter gasket has been known to cause problems, and cracked or perished fuel pipes are possible. Air in the fuel supply rarely causes any error codes or warning lamp, as it only affects starting unless the leak is really bad. The error detection systems don't really seem to work during cranking on these cars.

I fitted a non-return valve into the fuel line to the filter on mine, mainly to make changing the fuel filter easier. But before this I used to have the occasional fail to start on first crank attempt, though it fired up on the second. Since fitting the valve (2 years ago), it has fired first time, every time. (so far!)

Some info on this mod:

The mod is not a cure for bad air leaks, but will deal with tiny ones.

 

[wild_one]

17 hours ago, Tdci-Peter said:

£35 is only 28 litres at supermarket prices, a lot less at BP premium prices! So the tank is nearer half full. Seems like your gauge is reading not so far off mine, which is well above the actual tank content.

The symptoms do sound like a bit of air ingress to me. The fuel filter gasket has been known to cause problems, and cracked or perished fuel pipes are possible. Air in the fuel supply rarely causes any error codes or warning lamp, as it only affects starting unless the leak is really bad. The error detection systems don't really seem to work during cranking on these cars.

I fitted a non-return valve into the fuel line to the filter on mine, mainly to make changing the fuel filter easier. But before this I used to have the occasional fail to start on first crank attempt, though it fired up on the second. Since fitting the valve (2 years ago), it has fired first time, every time. (so far!)

Some info on this mod:

The mod is not a cure for bad air leaks, but will deal with tiny ones.

 

But, if I have a 'leak' wouldn't it produce symptoms all the time. I don't have starting problems. The only time I let the gauge run below what I thought was 1/4 and it wouldn't start until I poured a gallon of diesel in it? At the moment it appears my fuel sender is telling fibs about the amount of fuel actually in the tank. And is very consistent about that. As long as I keep the fuel gauge showing above 1/4 I could just ignore the problem. It's just that I'm a person that likes things to work?

I used to drive a mk1 diesel 1.8tdci and that had the opposite problem, it would underestimate the correct amount of fuel actually in the tank.

[wild_one]

Also, just out of interest, would air entering the system show as fluctuating fuel pressure, if I plug in my Forscan?

[Tdci-Peter]

20 hours ago, wild_one said:

would air entering the system show as fluctuating fuel pressure, if I plug in my Forscan?

With the engine idling, and low level in the tank, it would show, but I am fairly sure you will also hear changes or hesitations in the engine sound when air is getting in. While driving the fuel rail pressure fluctuates dramatically in response to the throttle & engine speed, so seeing little dips due to air would be much harder.

I still don't think your gauge is reading high, if anything it seems to be reading low. Taking about 28l from indicating 1/4 full to being brim full is a sure indication of this.

Filling the tank from near empty to full would be at least 50l, and cost a rather painful £62 or more!

That is why I am suspecting air leaks, as it is the next most likely problem. It seems the actual problem of bad starting happens rarely, and when the tank is getting low. Air leaks can be irregular or intermittent, and will get more likely as the tank level drops, and fuel has to be lifted higher up to the filter. The filter is the highest point, so will be most prone to air being drawn in.

[wild_one]

1 hour ago, Tdci-Peter said:

With the engine idling, and low level in the tank, it would show, but I am fairly sure you will also hear changes or hesitations in the engine sound when air is getting in. While driving the fuel rail pressure fluctuates dramatically in response to the throttle & engine speed, so seeing little dips due to air would be much harder.

I still don't think your gauge is reading high, if anything it seems to be reading low. Taking about 28l from indicating 1/4 full to being brim full is a sure indication of this.

Filling the tank from near empty to full would be at least 50l, and cost a rather painful £62 or more!

That is why I am suspecting air leaks, as it is the next most likely problem. It seems the actual problem of bad starting happens rarely, and when the tank is getting low. Air leaks can be irregular or intermittent, and will get more likely as the tank level drops, and fuel has to be lifted higher up to the filter. The filter is the highest point, so will be most prone to air being drawn in.

Thanks for the advice, I'll check things out. An air leak would certainly be easier to deal with than replacing the tank sender!

[wild_one]

is it possible to diagnose a failing lift pump, with the pump in situ?

[Tdci-Peter]

2 hours ago, wild_one said:

is it possible to diagnose a failing lift pump

There is no lift pump in the tank on any of the Focus Mk2 Diesel cars, 1.8, 1.6, 2L. The main diesel pump has to do all of the work of sucking fuel up out of the tank. That is why air in fuel lines can be such a problem.

[martyntdci]

What he ^^^^^^ said

[Voxxman]

Hi,

I had this issue on my Focus about 15 years ago. I spent a fortune trying to sort it. Sender units, fuel pump etc etc (£1200 on a diesel back then).  I had to make sure I kept the take 1/4 full.  Ford garage (who were trying to fix it) came out twice after me running out of fuel. I ended up keeping a gallon of diesel in the boot and ended up bleeding the the injectors on a few occasions myself.  It ended up being a concaved fuel tank (this is what my uncle said it was all along). Replaced the fuel tank and the problem was solved.  I was so peed off that I had spent so much money with the Ford garage that I got them to fit a new clutch for free as they wouldn't return the money I paid out for the pump.

[hippo4x4]

On 1/19/2019 at 4:19 PM, wild_one said:

My car seems to run out of fuel when the gauge is still showing 1/4 full. The gauge cluster passes the self test thing. It works correctly in every other way. I'm guessing either faulty sender or pickup. Does anyone have any experience of diagnosing the sender. Or, the process of removing it which appears to involve removing the fuel tank or cutting a hole under the back seat?

hi

 

 did you manage to find out the issue???

 

 I'm have the same fault with my 2015 focus

 

cheers 

[Tdci-Peter]

7 hours ago, hippo4x4 said:

 I'm have the same fault with my 2015 focus

The OP seems to have bought another car (petrol Fiesta) shortly after starting this topic! So it may not have been fixed.

The Mk3 Focus with the 1.5Ecoboost (GTDI) engine, which is I guess what Dean has, is a very different beast. A Petrol engine will usually have a lift pump in the tank, vapour locks due to the volatility of petrol are too likely otherwise. Fuel pumps, injectors and engine operating modes are very different.

Same starting point though: Use the filling station pumps to calibrate your gauge, by noting litres added from varying gauge needle positions at each fill. You will soon find out if the tank really is running empty, or just giving problems as the fuel level drops for some reason.

Next step is to use Forscan or a similar Ford specific system to look for error codes as soon as possible after an event. It can also give fuel pressures (I am pretty sure a GTDI engine has a pressure sensor.) and other info.

But diagnosing a modern GTDI engine is never going to be easy. They combine all the complexities of Diesel with those of fuel injected Petrol, plus a few quirks of their own!

[hippo4x4]

hi Peter

 

thanks for the reply.   mine is the diesel euro 6 engine i have started a post on here.   last time it cut out  it had half a tank i put 20 litres in and its almost full as i put an endoscope down the neck to check for sludge in tank and level was just below neck.

 

cheers Dean