Fuse Box Fuse 18 fuel pump - fault code p1020.

nod

Member
hi folks, i'm trying to solve a p0120 fault code,
Fuel Pressure Regulation: Control Range Exceeded
The car has a faulty connector on the fuel line to the fuel filter so I guessed that might be causing the fuel pressure issues. I've been checking fuses for power supply today and found fuse 18 is for the fuel pump and there is virtually no power getting to either side of the fuse, or the terminals in the fuse box when the fuse is removed. I assume there should be power there when the ignition is turned on?? the multimeter showed 0.3v on one side only, 0 on the other. Any ideas please?
 
hi folks, i'm trying to solve a p0120 fault code,
Fuel Pressure Regulation: Control Range Exceeded
The car has a faulty connector on the fuel line to the fuel filter so I guessed that might be causing the fuel pressure issues. I've been checking fuses for power supply today and found fuse 18 is for the fuel pump and there is virtually no power getting to either side of the fuse, or the terminals in the fuse box when the fuse is removed. I assume there should be power there when the ignition is turned on?? the multimeter showed 0.3v on one side only, 0 on the other. Any ideas please?
Is it p0120 or p1020 as title ?
as p0120 seems to indicate a throttle position sensor fault
Keith.
 
Hi,

the FSI pump runs for a few seconds when the driver's door is opened to prime the system but will then only run when the engine is running. If the engine isn't running, neither is the pump. You need to start the engine to see if the pump runs. If the pump doesn't run, the engine won't start!

The FSI has two fuel pumps, the low pressure pump which is electrically driven and moves the fuel from the tank to the engine. That's what fuse 18 is for.
There is also a high pressure pump which is driven by the engine camshaft. The FSI has a much higher fuel injection pressure (like a TDI) than a "traditional" petrol injection engine and so uses the high pressure pump to generate pressures between 50 and 100 bar in the fuel rail.

On the low pressure side, there is a mechanical pressure regulator. This controls the supply pressure to about 3 bar by acting on the return. There is also a electrically controlled "fuel metering valve N290" which is used to boost the pressure in the low pressure circuit for hot starting to prevent bubbles forming in the hot fuel lines in the engine bay.
I don't believe the low pressure side has a pressure sensor so wouldn't fault on that. If the low pressure pump isn't working correctly though or the pressure regulator is broken then there will be a fuel starvation problem on the high pressure side.

The high pressure side is controlled by the ECU. There is a fuel pressure sensor G247 and a regulating valve N276 in the fuel rail. To regulate the pressure, the valve lets excess fuel out of the rail to keep the pressure at the level the ECU wants.

Possible causes:

Low pressure fuel starvation. The high pressure pump isn't getting enough fuel so can't generate the required pressure in the fuel rail.

Faulty high pressure pump. The pump doesn't pump properly and can't reach the correct pressure.

Faulty pressure sensor. The reading is simply wrong.

Faulty regulating valve. If this is faulty, it it should stay closed (other than the mechanical over pressure release) and the pressure will be too high in the rail.

Are you able to use VCDS to record the measured fuel pressure in the rail? It would be useful to know the values for engine idle speed and also high revs.

regards

Andrew

48081
 
excellent schematic cheers. I've changed in tank pump, hp fuel pump and 9,10,11 are 2 years old so i expect them to be good. i read somewhere the changing N80 fixed someones issue, where is that part.

Also could it be that the relay 410 for the in tank pump has failed, hence no power at fuse 18, i'm sure there was no power there with engine running either...? i have a 410 in my other FSI so i'll swap that tomorrow and see what happens...many thanks
 
ps, Sorry don't have VCDs. suspect the issue is the fuel line connector letting air in and not getting upto full pressure. Will have replacement line next week to try. Fingers crossed.
 
excellent schematic cheers. I've changed in tank pump, hp fuel pump and 9,10,11 are 2 years old so i expect them to be good. i read somewhere the changing N80 fixed someones issue, where is that part.

Also could it be that the relay 410 for the in tank pump has failed, hence no power at fuse 18, i'm sure there was no power there with engine running either...? i have a 410 in my other FSI so i'll swap that tomorrow and see what happens...many thanks

Hi,

N80 is an air (or rather fuel vapour) valve rather than being part of the fueling system. It allows the engine air intake to suck evaporated fuel vapour from the fuel tank into the intake to purge the build up of vapour though the engine rather than just allowing it to build up and escape to the atmosphere and pollute. If the valve is broken (e.g. stuck open) then you will get too much air and a weak fuel mixture fault.

48084


I have circled the N80 valve. The hose goes to the right to join the intake between the throttle body and the EGR. To the left there is a metal pipe which goes to a hose that connects to the activated charcoal canister in the wheel arch. This traps the fuel vapour and is on the other side connected to the fuel tank.

If your in take electric pump is good and fuel filter is OK but the pressure is still too low then you could have a look at the low pressure fuel regulator valve. That's hiding on the left of the picture.

regards

Andrew
 
Thanks Andrew thats really helpful, I've already changed N80 valve without knowing thats what it as called, same time as HP fuel pump. i'll try fuel regulator if relay 410 and new fuel line don't fix it. I'll update when its fixed. cheers
 
I’ll definitely be following this thread on my 1.6fsi having same codes pop up and my fuel filter has been changed recently and I’ve noticed they have cabled tied the fuel line so it doesn’t pop off connectors look like they have had there day :(:)
 
ps, Sorry don't have VCDs. suspect the issue is the fuel line connector letting air in and not getting upto full pressure. Will have replacement line next week to try. Fingers crossed.
Hi nod is there a link to the fuel lines ?
 
hi louis i got the fuel line off @Clackers who kindly took the line off his breaker. I'm sure someone else on here, @A2Steve can help you out with a replacement line with decent connectors? i saw that steve has 2 fsi's at the moment.. i'll update once the line has been changed to see if it fixes the problem cheers.
 
just to update. i've changed my fuel line to one with good connections, and the fuel pump relay. still got the fault code...really it can only be the fuel metering valve N290 or the fuel pressure regulator......
 
Hi nod I know what my issue is fuel pressure sender and fuel pressure regulator valve all in the intake manifold :mad::)
 
hi louis, how did you narrow it down to those parts? on my car they were changed 2 years ago, so i've been assuming they are still good....cheers
 
I changed the intake manifold as my rod had snapped on the (original) one so I got one off a donor car of gumtree he’s said it’s fully working so I bolted it to the car all was well then I went to take engine management light out with my scan tool and this came up as shown below
48382

I had fuel pressure problems when I got the car so I changed hp fuel pump
And fuel pump (Tank) also fuel filter and the fuel pressure codes went out and they stayed out. Until I changed the manifold

So what I’m going to do is take it off again (intake manifold) and put my fuel pressure regulator and fuel pressure sender from the original what was working fine

Hopefully this solves the issue
 
Hi,

the FSI pump runs for a few seconds when the driver's door is opened to prime the system but will then only run when the engine is running. If the engine isn't running, neither is the pump. You need to start the engine to see if the pump runs. If the pump doesn't run, the engine won't start!

The FSI has two fuel pumps, the low pressure pump which is electrically driven and moves the fuel from the tank to the engine. That's what fuse 18 is for.
There is also a high pressure pump which is driven by the engine camshaft. The FSI has a much higher fuel injection pressure (like a TDI) than a "traditional" petrol injection engine and so uses the high pressure pump to generate pressures between 50 and 100 bar in the fuel rail.

On the low pressure side, there is a mechanical pressure regulator. This controls the supply pressure to about 3 bar by acting on the return. There is also a electrically controlled "fuel metering valve N290" which is used to boost the pressure in the low pressure circuit for hot starting to prevent bubbles forming in the hot fuel lines in the engine bay.
I don't believe the low pressure side has a pressure sensor so wouldn't fault on that. If the low pressure pump isn't working correctly though or the pressure regulator is broken then there will be a fuel starvation problem on the high pressure side.

The high pressure side is controlled by the ECU. There is a fuel pressure sensor G247 and a regulating valve N276 in the fuel rail. To regulate the pressure, the valve lets excess fuel out of the rail to keep the pressure at the level the ECU wants.

Possible causes:

Low pressure fuel starvation. The high pressure pump isn't getting enough fuel so can't generate the required pressure in the fuel rail.

Faulty high pressure pump. The pump doesn't pump properly and can't reach the correct pressure.

Faulty pressure sensor. The reading is simply wrong.

Faulty regulating valve. If this is faulty, it it should stay closed (other than the mechanical over pressure release) and the pressure will be too high in the rail.

Are you able to use VCDS to record the measured fuel pressure in the rail? It would be useful to know the values for engine idle speed and also high revs.

regards

Andrew

View attachment 48081
hi Andrew i've finally got around to looking at the fuel pressure with vcds. i'll attach some screenshots to show what vcds found once the engine was up to temperature. what i observed was that the first 'absolute pressure' reading, the higher figure was steady at a given rev setting whatever the engine temperature, but the lower 'absolute pressure' figure reduced at a given rev setting as the temperature increased. So i guess that means the issue is in the low pressure side of the fuel system? the figures look too high compared to the schematic which suggests 3-5.8bar on the low pressure side.
Do you understand why increased temperature would cause the fuel pressure to drop?
At idle (about 680 to 720rpm) the initial low pressure reading was around 7 bar with a cold engine, as the engine temp increased the low pressure reading dropped at idle until the engine stalled at around 5 bar.
Also the low side fuel pressure reading halved, when comparing the pressure with a cold engine and up to temperature engine. At about 3000rpm the low pressure was around 20-21bar, with an engine up to temperature the fuel pressure dropped to around 10 bar at 3000rpm.
any ideas what would cause these readings appreciated.
to date ive changed all parts except the n290 , the injectors, manifold and activated charcoal canister. cheers
 

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hi Andrew i've finally got around to looking at the fuel pressure with vcds. i'll attach some screenshots to show what vcds found once the engine was up to temperature. what i observed was that the first 'absolute pressure' reading, the higher figure was steady at a given rev setting whatever the engine temperature, but the lower 'absolute pressure' figure reduced at a given rev setting as the temperature increased. So i guess that means the issue is in the low pressure side of the fuel system? the figures look too high compared to the schematic which suggests 3-5.8bar on the low pressure side.
Do you understand why increased temperature would cause the fuel pressure to drop?
At idle (about 680 to 720rpm) the initial low pressure reading was around 7 bar with a cold engine, as the engine temp increased the low pressure reading dropped at idle until the engine stalled at around 5 bar.
Also the low side fuel pressure reading halved, when comparing the pressure with a cold engine and up to temperature engine. At about 3000rpm the low pressure was around 20-21bar, with an engine up to temperature the fuel pressure dropped to around 10 bar at 3000rpm.
any ideas what would cause these readings appreciated.
to date ive changed all parts except the n290 , the injectors, manifold and activated charcoal canister. cheers

Hi,

Thanks for posting your readings. I'm not sure what that third pressure value is, I will need to look into that. I don't think there is a sensor on the low pressure side so the ECU won't know what that is. I will check the values on my FSI and compare with yours. I'll probably be able to do that in the next couple of days (rain permitting!).

Interesting regarding knock sensor fault. I think the knock sensor and pressure regulator and sensor wiring goes in the same loom on the back of the engine. Could anything have been damaged there?

regards

Andrew
 
hi andrew, the knock sensor is a problem @A2 Louis had along with the same fault codes i have for fuel pressure and set point not reached.. I too am suspecting electrical issue but i'm very much guessing, as I'm pretty amateur at this stuff. I did check voltages at the vacuum control switch for the set point not reached issue and found 10.8v, where i thought it should be on a 5v circuit from looking at elsawin, but i don't pretend to understand car electrics. I have another FSI, so I'll plug into that one and update on the fuel pressure values I get later.

cheers
 
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