Fuel gague problem after high pressure pump is replaced

[Camel]

Hi All, I have a funny problem with my W203 270 CDI (2001).

I recently broke down, and the fault turned out to be the high pressure fuel pump. I had it replaced, along with the fuel lines as recommended by my local garage (not MB dealer).

Since then, they advised that coincidentally the fuel gauge is faulty, and at 1/4 tank the car runs out of fuel.

However, when I fill it up, it doesn't take a full tank - there is obviously fuel in there.

My gut feeling is there is fuel in there, but it's not getting to the engine. Could it be some sort of air lock or something? I have no idea, but I would like to be able to go back to the garage and tell them what the problem might be so they can fix it. Goodness knows it's cost me enough so far!

Thanks in advance for any help,

Chris.

 

[star]

Check the tank hasn't collapsed/ been sucked in.

 

[Camel]

Check the tank hasn't collapsed/ been sucked in.

Thanks mate. Is that a common problem? Could it have been done as part of the high pressure pump replacement process? I am also trying to understand how / why this mght happen.

 

[jj1975]

Hello
once i run out of fuel and for some reason after that the car wasn't leveling the fuel tanks so for 2-3 months i had to not let the tank go less the 1/2 after slowly i was letting the fuel go under 1/2 keeping a small container with fuel in a boot that was a year a go and now its fine but still i dont let the fuel to go under 1/8 normally i fill up around 1/4 of the tank i dont want to risk again
Maybe this can help

 

[panason1c]

Could it have been done as part of the high pressure pump replacement process? I am also trying to understand how / why this mght happen.

Perhaps the garage that replaced the hp pump and fuel lines used a high pressure air line to blow down the fuel lines to give them a good clear out and inadvertently blew off the fuel pick-up pipe located inside the fuel tank, i would remove the fuel tank sender/pick-up pipe to check for this?

 

[star]

perhaps the pump wasn't "faulty" and the car had no fuel in it when it broke down, thus giving the impression that the pump was faulty due to the lack of pressure??

 

[Camel]

Thanks for all the replies - I would have replied earlier but my internet is down at home (damn you Virgin media) and for some reason this site is blocked by Orange on my iphone!

Anyway....JJ, appreciate your comments - I will certainly fill up before it gets too low.

Panason1c - Thanks for the tip I appreciate that.

Star - I hope to goodness that is not the case, or I have thrown money away When I fill up, the amount of fuel in the tank according to the gauge is pretty accurate, compared to the amount I put in.

 

[Camel]

Well I just spoke to these guys, who I have used once before to fix a minor problem I had.
http://www.prestigeservicing.co.uk/

The chap there said that it could be the high pressure fuel pump not creating enough pressure to get the last of the fuel out in the saddlebag tank.

He also said it could be the sender unit, but I think it is unlikely that it would break at the same time.

Now, I can't remember the exact amount of fuel the car had in it when it broke down, but I believe it was low. So I can see too possible causes....

1) The high pressure fuel pump was never at fault - it was the sender unit all along, and the wrong part has been replaced....and putting more fuel in has fixed the problem. (Jeez I hope not.)

2) The new high pressure fuel pump is not making enough pressure to get that last bit of fuel out of the tank. This can be checked on the star system I believe, and also possible on other car computers.

Finally, I guess my last option is to always keep it full of fuel. Which is definitely the cheaper option, but my OCD personality might not be able to cope with this situation

 

[jj1975]

Well I just spoke to these guys, who I have used once before to fix a minor problem I had.
http://www.prestigeservicing.co.uk/

The chap there said that it could be the high pressure fuel pump not creating enough pressure to get the last of the fuel out in the saddlebag tank.

He also said it could be the sender unit, but I think it is unlikely that it would break at the same time.

Now, I can't remember the exact amount of fuel the car had in it when it broke down, but I believe it was low. So I can see too possible causes....

1) The high pressure fuel pump was never at fault - it was the sender unit all along, and the wrong part has been replaced....and putting more fuel in has fixed the problem. (Jeez I hope not.)

2) The new high pressure fuel pump is not making enough pressure to get that last bit of fuel out of the tank. This can be checked on the star system I believe, and also possible on other car computers.

Finally, I guess my last option is to always keep it full of fuel. Which is definitely the cheaper option, but my OCD personality might not be able to cope with this situation

Hello Camel
first sorry for my poor english
Now when i had the problem with my car been reading alot to find out what was the problem and i did find a answer somewhere in this forum
2 clear fuel pipes goes to HP pump 1 from fuel filter bring fuel to it and the other 1 is return fuel to tank which activate the pump there to level the fuel in both tanks from what i have reading in HP pump is valve with a sphere to let fuel to return and the sphere stuck open and if you check the return fuel line you can see air in it when you accelerate
after some time the air it goes it self and the leveling pump in tank start to work properly
I hope this make some sens to you

 

[Camel]

Thanks JJ I appreciate your comments. I think I may just give it time and see what happens

 

[Camel]

Well this is still bugging me!

Can anyone advise, how easy it is to check the fuel sender unit?

I have also been advised that it is possible, with a computer, to check the pressure being made by the high pressure fuel pump, as this might be the fault. Does anyone know if that can only be done on a STAR system, or could it be done by my garage that "fixed" it?

 

[rpe2]

My old c class was the same. The fuels was being returned to the wrong side of the saddle tank owing to a duff valve in the high pressure pump.

I simply kept it above 1/4 full.

Was your pump a new one?

 

[Camel]

My old c class was the same. The fuels was being returned to the wrong side of the saddle tank owing to a duff valve in the high pressure pump.

I simply kept it above 1/4 full.

Was your pump a new one?

Yes, my old pump was replaced with a brand new one - I am advised by my garage. But I will be heading up to talk to them at the weekend about how my fuel gauge is not faulty.

 

[Camel]

Well for anyone who is interested, I spoke to a merc specialist today (I had my thermostat replaced) and asked about this problem. The guy I spoke with seems to think that I have had the wrong part replaced, and it's the sender unit all along. So goodness knows where I stand with this and my garage......I guess it's just one of those things.

I spoke to Dronsfield and they have a pair of used sender units - they normally go for £125. So I might get them and have them fitted.

Does anyone know if this is a complex job?

 

[Camel]

Well time to drag up an old post...

This issue has still been going on, so all I've done is not let the tank get to 1/4 full. I've talked to loads of people about this, and a lot have said sender units are at fault. But I raised it with the garage who did the repair originally, and they suggested that next time it gets to the point where it will fail, run the engine with the fuel cap off.

So I did this today, and ran it to below 1/4. Then this evening I put the cap back on - thinking it would then go back to the way it was (no idea why I thought this!). But I took it for a massive thrash, blew the cobwebs out and ran the tank down to 1/8th full.

My plan is to run it until reserve comes on, then fill to about half, and if the problem is cured.

This is obviously good news for me.....but my question is, why would this help??

Oh, and I am carrying a 5 ltr can of fuel with me!