Clk 270 cdi fuel just in one side of tank?

[alf1956]

Hi fellow members
I have a 55 plate Clk 270 cdi & I am having problems with the diesel getting to the engine. I recently drained the diesel tank as I had some contaminated fuel in the diesel tank by taking off both of the round cover on the fuel tank & inserting a pipe to suck all the fuel out I then put in 25 litres of clean fuel & ran the car for a while then today the car cut out & would not start & we noticed that the diesel was not getting through & the so we put on a manual inline pump that you press & it pumps the diesel through & the car started but when we took off the manual pump & put the pipes back on the car would not start so we took out the back seat & took off both the round covers on the diesel tank & noticed that the drivers side half of the tank was empty but the passenger side half was full (the diesel tank is like a saddle bag shape with two halves which are connected) so we put some diesel in through the filler which went into the drivers side half of the tank & the car started up & ran no problem but I am now worried about taking the car out in case the same thing happens & the diesel goes from the drivers side & the car cuts out as it seems to be that the diesel feed to the engine is supplied from the drivers side half of the tank but somehow the diesel is not coming over from the passenger side half of the tank? We have had both the sender unit on the passenger side & the drivers side unit out of the tank to see if the connecting pipes were blocked etc but they all seem ok. ​

 

[alexanderfoti]

Whew, big block of text there.

The saddle tanks use a siphon of the return from the HP pump to equalise the tanks with the engine running.

Normally, this is caused by a faulty high pressure pump, however, as you have had contaminated fuel, its possible that the siphon nozzle is blocked.

As long as all the pipes are connected correctly then I would look at the HP pump.

 

[Westheath]

Yep if the fuel tanks low pressure lines are clear of contamination the High pressure pump isn't returning fuel correctly,
the passengers side saddle tank will be full and the drivers side empty.

Make sure the filter on the bottom of the tank pumps clean as well.

 

[davemercedes]

Well, well... you live and learn!
- Good luck with sorting it out, alf1956.

 

[alf1956]

I am still having issues with the saddle tank scenario & the car cut out yesterday & when we looked in the tank the drivers side half of the tank was empty. I have had an engine fitted & it came as a bare block with no ancillaries on it so w ehad to take them all off my old engine had problems since then so i am wondering if when replacing all the fuel lines etc they may have got one on the wrong way round, I know the main metal fuel lines from the tank are different sizes so they will be correct but then there are quite a few other fuel line connections on the engine itself & to the high pressure pump & maybe the 2 pipes to the high pressure pump have been fitted the wrong way round as i have had a replacement high pressure pump fitted which was checked out by a local diesel injection specialist prior to fitting

 

[alexanderfoti]

I am still having issues with the saddle tank scenario & the car cut out yesterday & when we looked in the tank the drivers side half of the tank was empty. I have had an engine fitted & it came as a bare block with no ancillaries on it so w ehad to take them all off my old engine had problems since then so i am wondering if when replacing all the fuel lines etc they may have got one on the wrong way round, I know the main metal fuel lines from the tank are different sizes so they will be correct but then there are quite a few other fuel line connections on the engine itself & to the high pressure pump & maybe the 2 pipes to the high pressure pump have been fitted the wrong way round as i have had a replacement high pressure pump fitted which was checked out by a local diesel injection specialist prior to fitting

The car wont run with the clear fuel pipes fitted the wrong way round.

There is a lift pump above the high pressure pump.

Its possible that the pipes are the wrong way round at the tank, or where they transition from tank to hard lines at the back of the car.

 

[alf1956]

The fuel pipes at the tank have not been touched as there was no need to touch them.

 

[alexanderfoti]

The fuel pipes at the tank have not been touched as there was no need to touch them.

I think its very unlikely the pipes are the wrong way round, if you think they are though, swap them at the at the bulkhead and see how it runs?

The pipes are quite complicated, but it goes:

bulkhead - > preheater > fuel filter - > lift pump - > hp pump

then return from the HP pump to the back of the rail. You also have the return from the injectors that connects to the back of the rail with a banjo bolt, that also connects to a pipe that goes back to the fuel/heat exchanger. The fuel then goes from this back to the tank.

If I where you, I would connect a clear hose in the return back to the tank, in the engine bay, and check for return flow back to the tank.

 

[mercedes13156]

The car wont run with the clear fuel pipes fitted the wrong way round.

There is a lift pump above the high pressure pump.

Its possible that the pipes are the wrong way round at the tank, or where they transition from tank to hard lines at the back of the car.

The two fuel lines under the HP Pump have a steel collet holding them in. The pipes are formed so that they fit in neatly to the pump and the cutouts on the collet line up perfectly with the "shoulders" on the pipe end fittings. If you get them wrong, they have to be forced and that usually breaks the plastic pipe ends when you screw the collet down.

 

[andrew056]

Had the same problem with a petrol CLK drivers side empty passenger side full , fixed with a new pump in the tank .

 

[andrew056]

Just checked the invoice for the repairs to the CLK it was the fuel tank sender unit that does the siphoning from tank to tank and that was what was replaced not the pump, that was OK.

 

[Bdmdel]

Just checked the invoice for the repairs to the CLK it was the fuel tank sender unit that does the siphoning from tank to tank and that was what was replaced not the pump, that was OK.

Hello Andrew,

I am having exactly the same issue with my clk 2005, but the garage I went to replaced so far the fuel pump, and filter only after starting to investigate myself I realised the engine would cut off whenever the fuel reader was less than half of the tank and upon check I realised that drivers side of the tank is empty while passengers has enough fuel. So now I don’t want to go back to the same place and I was wondering if you could share the details of your mechanic or garage although I live in London I wouldn’t mind to travel if I would know they do a good job

 

[alexanderfoti]

We are not too far from most places in London and can quickly test if your return flow is enough to balance the tank or if your issues is with the delivery unit.

 

[Bdmdel]

We are not too far from most places in London and can quickly test if your return flow is enough to balance the tank or if your issues is with the delivery unit.

How could I get a contact number? Or any contact details?

 

[alexanderfoti]

How could I get a contact number? Or any contact details?

Our number is 020 3384 4644

It should show up in our signature, but may not if you are mobile.

 

[Bdmdel]

Our number is 020 3384 4644

It should show up in our signature, but may not if you are mobile.

Yes, I am using a mobile. I will be leaving in a few days and be away for a few weeks but i will get in touch as soon as I am back. At the moment the quick fix that I using is to keep the fuel tank full and fill up after every journey.

 

[alexanderfoti]

Yes absolutely, If you keep it above half a tank, it will be fine.