TD4 2004 fuel pressure

Please help, I'm off the road and not earning as a result

Could anyone out there measure the voltage they have on the low pressure fuel sensor under the fuse box. please?

My TD4 was running but had an intermitant judder and cut out once in a while like there was a lack of fuel so I started with changing the fuel pump(wheel arch) and filter + cleaned the in tank pickup filter. And it was not started since.

The low pressure sensor appears to be stopping the high pressure pump actuator hence no fuel at the fuel rail.

I just replaced the LP sensor in case that was faulty but still no joy.

Can anyone tell me what voltage I should have on the LP sensor please.

5V supply
- feed
1.34V when wheel arch pump running. This is the one I'm after.

Is there any kind or reset required on the ecu?

Am a tad confused, but its ok, im blonde!

So you had an intermittent juddering, so you replaced your lowside fuel pump and filter, as well as removing your tank sender and cleaning the filter on that?

Then you tried to start it and it wont start at all?

...........I'm thinking you did something wrong


Have you bled up the fuel system? Now i know its an automatic bleed, but leaving the ignition on for a minute , cycling it and repeating a few times before you crank is the ideal thing to do. Cranking with a fuel system full of air can just trap inside your HP system and cause it to be a bit of a pain to start.

If you did bleed it , it makes me think you did something wrong.

Fuel filters are directional (they have an arrow).

Fuel pipes are easilly kinked when refitting the lowside fuelpump carrier assembly.

Stuff is easy not to plug back in

Are you getting fuel to your HP side on ignition on?

Can you feel the lowside pump working?

If you disconnect a lowside pipe in the engine bay and aim it into a container ,are you getting pressurised fuel upto that HP pump?

If (you have the tools and skillz and) you slacken off one of the unions on the high pressure side of the system, then turn IGNITION ON ONLY, do you get a feed of fuel? If so tighten it backup!

If you get all that and its ok , try kicking the car and swearing for a while!

Thanks for the reply buddy.

I did check all visable pipes for bends etc before switching on. I'll have a look all round again just to be sure.

I have had the inlet manifold off and cracked open the HP fuel lines. No fuel at the injectors unless I pinch the LP supply pipe(with pump running)! I think as the pressure increases the ECU energises the HP pump pressure regulator and fuel flows to the injectors. Otherwise it is diverted back to the tank.

I dont have a fuel pressure tester but I do have a voltmeter(I'm an electrican) I could do with the operating voltage range required by the ECU from the LP pressure sensor to confirm the fuel low pressure is ok....

I'm pretty sure that the HP pump lets the lowside fuel freeflow through it whilst ignition is on 2, like a self prime system.

Then on cranking it obviously forces it through, if your not getting fuel to your injectors with ignition on 2, it suggests to me that you have a restriction in your system. Are you sure the fuel filter is fitted in the correct orientation?

I would suggest a simplistic approach to this fault if im honest. I can understand as a sparky you want to get your multimeter into everything and try and understand it as an electrical circuit.

Honestly though , since its a lowside fault. I'd go with unplugging stuff seeing where there is fuel.

Jack the car up, remove the o/s/r wheel, access the pump in a way in which you can see it. Unplug the pump output pipe, aim it at a bucket, ignition 2. Is it ****ing out?

If yes, then you need to unplug the output from the fuel filter, aim it at a bucket , ignition 2, does fuel **** out at the same rate as it ****ed out the pump?

If no, then you need to head back into your tank and check what you left unplugged / incorrectly routed / there is no fuel in your car.

If you did get fuel coming out your fuel filter at the same rate at which it came out of your pump, head up the car and unplug the pipes after your lowside fuel pressure sensor (underneath your o/s/f wing). Is it ****ing out at the same rate it came out of the fuel filter?

This sort of system would be quick and effective in my opinion. I'm thinking fuel filter is in the wrong way around still personally, or a slight kink in one of the pipes inside the lowside fuel pump housing.

It sounds like you have a restriction between the lowside pump and the highside pump, since your not getting fuel at your common rail.

Goodluck and i hope your not being forced to spanner in the rain, as its miserable as hell where i am. Happy hunting

Soaked to the skin with rain and diesel!

Tried all of the above. Same flow rate after the pump, filter(correct way around, marked with arrow on the side and out on the top) and also in the engine bay after the lowside fuel pressure sensor and at the HP pump inlet.

But the said flow rate is not what you would call fast. All pipes are in the correct positions. And I've tried the old pump again but it makes no difference.

Leakback test your injectors!

Definate next step i think, since i have no voltages to give you off the top of my head.

Also you can tighten the pins up on your HP fuel rail sensor and check there is no corrosion in there.

Someone else might have more ideas?

But i personally dont concern myself to massively with lowside fuel pressure, if its getting there in decent quantity there is generally pressure. You only need around 140kpa to start the car and a new pump with do 370kpa at ignition 2 normally. Around 440kpa when running (i thinks).

late commenting i know but definitely agree on suspect leaking injector or pressure regulator seal...

Result! This info would have saved me time and money so here it is...

Sedimenter sucking in air. Once removed the engine started first time!

Been starting and running perfectly for the last week or so and the occasional lack of power has gone. It must have been dodgy for some time and once I disturbed it while putting the new pump in, it got so bad that the pump could not deliver enough pressure. The pipe seals are not the best after 7 years I think due to the swivel joints. I'm going the put a disco sedimenter in as a replacement as they are cast metal with proper pipe terminations.

I now have a 2 spare fuel pumps(one new and my original) and low pressure fuel sensor if anyone is interested.

Hope this helps someone.

if the filter on the end of the pipe on the intank fuel pump was that bad then do not sell the intank fuel pump if thats what you brought as that much presure has been put on the pump it will fail as mine did after one week please do not disregaurd this message as being foolish hope this helps

teddywood1 said:

if the filter on the end of the pipe on the intank fuel pump was that bad then do not sell the intank fuel pump if thats what you brought as that much presure has been put on the pump it will fail as mine did after one week please do not disregaurd this message as being foolish hope this helps

Click to expand...

He doesn't have an in tank pump...its a 2004 td4 so low pressure, filter and sedimenter near right rear wheel arch and high pressure pump front left of engine.