230E W124 Fuel Gauge issues

[230Eguy]

Hello everyone,

found another issue with my W124 that left me stranded on the motorway.

It appears that my fuel gauge would indicate 1/4 tank left when in fact its bone dry. The weird part is the fuel warning light does come on even when the needle shows anywhere between 0-1/3 full....

I've looked through the web and gather it might be the fuel sending unit?

How do I best start to diagnose the problem? And if it is in fact the fuel sending part, can it be repaired/ cleaned or does it require a costly replacement?

Many thanks guys!

 

[Dec]

Cheapest test to try first is get a 250ml bottle of STP Fuel Injector cleaner and put in tank and top up, worked for me.

Dec

 

[Sp!ke]

Trust the reserve light, ignore the needle is my advice. You should get around 400 miles to a tank before reserve. Trip meter + reserve light light works for me. I replaced the sender once in the past and it failed again some 18 months later so never bothered again.

I believe its the detergents and additives in modern fuels that causes the problem.

 

[230Eguy]

Yupp that makes sense - only problem is that the odometer and trip meter don't work either... :-( so all I would have is to rely on is the light...

Did you replace the whole unit? Is it difficult to do and how much was it ?

Cheers!!

 

[Dieselman]

Pull the gauge sender out of the tank and check the float. You can access it from the boot by undoing the bayonet fitting and lifting it out.
TANK.

The Odo is probably the little nylon gear in the speedo housing is split, but before stripping it just make sure the zero reset knob hasn't jammed.

 

[230Eguy]

Hi Dieselman,

Where in hte boot is it located? Is it down in the spare tire well?

I've had a look but it didn't jump out at me immdediately...

Cheers!

 

[Ian B Walker]

The fuel tank sender unit on a saloon or coupe is behind the carpeted bulkhead of the boot. Pull carpet away and it is bang in the centre looking at you. A new one is £89 from the dealers but I feel sure that a more economically priced one should be available.

 

[bolide]

A new one is £89 from the dealers but I feel sure that a more economically priced one should be available.

My TR4 has an economically-priced fuel gauge - it's called a stick

It's also multi-tasking - it can hold the boot lid open as well!

Nick Froome
www.w124.co.uk

 

[Dieselman]

And be used to beat the car when it breaks down...

 

[230Eguy]

So, I found the unit - thanks Ian! I disconnected the the plug from the unit while the ignition was on and the gauge dropped to Empty. I've heard that this indicates a faulty sender unit - and that if it were working appropriately the gauge would show full. Is this correct ?

Where can I order a unit that is a bit more affordable than teh 89pound that Ian quoted....?

Thanks!

 

[Ian B Walker]

Try GSF or Euro Car Parts.

 

[Dieselman]

So, I found the unit - thanks Ian! I disconnected the the plug from the unit while the ignition was on and the gauge dropped to Empty. I've heard that this indicates a faulty sender unit - and that if it were working appropriately the gauge would show full. Is this correct ?

No. The gauge should show full when the lead is grounded, it will show empty if disconnected.

Pull the sender out of the tank and have a look to ensure it's not sticking.

 

[blondebier]

Where can I order a unit that is a bit more affordable than teh 89pound that Ian quoted....?

Hi 230EGuy, Not sure if you have resolved this one yet, but I had the same issue.

I found one here :

http://cart.euromercmercedesparts.co.uk/index.php?p=product&id=1464&parent=1

£49.99 + shipping

Genuine MB part too.

 

[Howard]

Yep , Euromerc are good guys !!

 

[blondebier]

So I ordered one from Nick - arrived next day! Well packaged in bubble wrap.

Has a warning sticker on it. Yikes!

Remove the safety pin before installation...

Here's a view from the top :

Here's a view of the bottom :

I'm guessing the safety pin is the bit on the bottom? Do I just pull it out?

Any other tips before I embark on this operation? I would normally just dive straight in, but as fuel is involved I thought I would ask. Is it safe to just unscrew the old one and put this one in it's place? Would it be prudent to disconnect the battery beforehand?

Any help would be most welcome if you've done it before.

Cheers,

Blondebier

PS. Mine is the TE version, so might be slightly different from the saloon...

 

[blondebier]

When I replace this does it require a gasket change too?

It didn't come with one... does it need one?