S320 Cdi Fuel pressure switch failure.

[franey]

Hi.
S320 cdi not starting. Had new injector seals, new alternator, new turbocharger and mechanical fuel pump.
Diagnostics point to the fuel pressure switch at the rear end of the common rail.
However, mercedes now state that you cannot buy this part £250 and must buy the complete rail with sender and switch attached. Car refuses to start.
Anyone had similar problems?
A Bosch equivalent is available (only the switch) from the Fatherland somewhat cheaper.
If you had this problem, did replacing the switch cure it?
Cheers.
Sorry on wrong section, OOPS!! help.

 

[W210 Fan]

Just had the same problem with my Audi, went to an indi, part was £37 and £65 to fit including an oil and filter change, take it to an indi, they will ring a motor factors like GSF who will know the bosch part number as it probably is a bosch part anyway and get it and fit it for you.......

 

[jaymanek]

We normally just change the seals on the switch which normally cures it, we have never had to replace the actual switch... the seals are available from MB for pennies..

 

[franey]

News just in.

New part arrived this morning. I fitted it, connected the harness and hey presto, Yippeeeee.................same as before. Won't start.
I sat in it and carressed the wheel very gently but alas, there was no fooling her.........ideas anyone?

 

[Dieselman]

It could well be the pressure control valve on the other end of the rail.

The sensor just reports what it sees..

 

[franey]

Thanks for your reply diesel man.

This really is a right nuisance!

Friend came with a code reader and it showed P2021. I googled it and it went on about a starter relay? Huh.??

 

[franey]

BTW, it was the switch thing I replaced, not the sensor. Sensor is at front engine, switch at rear?

 

[BlackC55]

Its a fuel pressure monitor/regulator. Starts with a 611 number. The sensor at the front is just as DM says.

Is the fuel filter full of fuel?

 

[BlackC55]

Oh and by the way if the fuel pressure is low in the rail it will bring up the fuel presure monitor/regulator as faulty as a fault code. It does this because it does not read any pressure.

 

[franey]

I took the pipe off the fuel filter (inlet) and turned on the ignition. Fuel flowed freely.
I will go and check for fuel coming out. Thanx


Checked fuel, is being delivered to injector pipes.

 

[jaymanek]

Checked fuel, is being delivered to injector pipes.

thats not really good enough... for a CDI to start there has to be over 200 bar at the pipes!

I have 2021 being the manifold air control actuator switch..

 

[franey]

Thanks Jayman.

So, it would appear that the fuel is not at a high enough pressure?

For it to be at a high enough pressure, the final pump (at the front of engine) should be delivering it at the 200 bar required.

Therefore on turning over (without starting) the fuel should really squirt out big style?)

If it is not, which it isn't , then there are two electrical thingy's on the pump. One could be a shut off valve (?) and the other looks like a temp sender.
One could therefore guess that the shut off valve is not opening.

If it is not opening, either it is faulty (which I thought would have given a fault code) or something is telling it not to open.

Perhaps a fuse could protect it?

If I switch the ignition on and then disconnect the wire from the shut off valve should I hear the thing click?

Thank you again.

 

[television]

Has anyone thought about the crankshaft sensor, has it been checked,,should be 1k ohm

 

[Ultymate]

There may be an immobiliser issue Oh a P.S. as well you should not be undoing pipes to check for pressure when working properly it's enough pressure to fire the diesel through your skin and into your blood stream, worst case scenario can be fatal.

 

[franey]

Thanks ultymate.

Yes I take your point about the high pressure too.

I agree there could be an immobiliser issue, but how would you for example reset the key to the car ?

Cheers. B

 

[Ultymate]

I'm not sure whether the diesels are immobilised by DAS system on the key, hopefully someone with more in depth info will chime in for you, sadly I don't think the keys can be programmed

 

[Dieselman]

Similar to jay's code.

P2021 Intake Manifold Runner Position Sensor/Switch Circuit Low

The immobiliser is a red herring, if the DAS3 isn't working the engine won't turn over.

 

[franey]

Thanks DM.
That clearly eliminates the immobiliser theory.
I have noticed that there is an electrical part on the intake manifold.
It makes a constant high pitched whistling noise. I looked the part up on the epc and it is the EGR valve. Is the whistling noise normal?

 

[television]

Thanks DM.
That clearly eliminates the immobiliser theory.
I have noticed that there is an electrical part on the intake manifold.
It makes a constant high pitched whistling noise. I looked the part up on the epc and it is the EGR valve. Is the whistling noise normal?

The EGR valve does not make a noise unless its leaking, many people disconnect it (its not needed) and plug the vacuum pipe.

The valve itself sits in the exhaust manifold and returns gases to the inlet under light running conditions to re cycle them

 

[panason1c]

The EGR valve does not make a noise unless its leaking, many people disconnect it (its not needed) and plug the vacuum pipe.

You can't disconnect and plug the egr vacuum pipe on a CDI, the complex electronics sense the disconnection and put the engine into 'limp mode'

(I know 'cos i've tried it)