W124 300e 24v fuel pump woes.

[tone capone]

Hi All.
Infuriating problem with my fuel pump. The pump will fire up intermittently and I thought I had made some progress when I recharged the battery and the pump worked but it would stop working shortly after. The car will drive fine (once it starts). Today I discovered wires taped together and looking decidedly ropey (see pic). I get the impression that this is an electrical problem rather than directly related to the pump itself. Pics attached
Thanks for all help. Rory

 

[grober]

Could be a dodgy fuel pump relay--- or it was quite common to interupt the supply to the relay coil by an after market alarm- what you may be seeing is a rewire after the alarm has been removed. No option but investigate under that taped repair other possibility is a problem with the fuel pump/s- when was the filter replaced last

 

[tone capone]

Thanks Grober.
Don't know when it was replaced last but will have a look at the wiring tomorrow. Is it worth changing the fuel filter by itself?

 

[wrdcc01]

T

 

[grober]

If you don't know when it was changed last-yes- make sure to fit it the right way round.

 

[optimusprime]

I would check the fuses first to make sure they are making good contact . And as grober said above , the fuel pump relays can be a problem on these cars after a few years . But if FPR is faulty i would think it would stop after first starts ,or not start at all .You say it fine ones its running ,,,Not forgetting the CPS .Along with the HT system how long as the distributor, and rotor arm , been on the car. Also the ht leads and plugs could be in need of replacing, it is all to do with engine running condition or failure .

 

[tone capone]

Thanks very much folks. Should be able to manage a fuel pump filter change. The fuel pump relay is incorporated into the MAS module on this model, if that makes a difference? The electricals might be a bridge to far for me so might have to pay someone

 

[optimusprime]

See it now 24 valve .

 

[ray_hennig]

The fuel pump relay is incorporated into the MAS module

Yes, and usually very reliable.

R

 

[tone capone]

Yes, and usually very reliable.

R

Discovered more ropey looking wiring under the passenger footwell. I'm guessing this will be attached to the central locking module under the rear seat? Why can't people leave these cars alone?

 

[wrdcc01]

If you do happen to trace a fault back to the MAS, there is a pcb connection between the pump relay and the output pin on the module that is often the source of no output as it melts with over current..

 

[carat 3.6]

Discovered more ropey looking wiring under the passenger footwell. I'm guessing this will be attached to the central locking module under the rear seat? Why can't people leave these cars alone?

That is indeed the central locking harness.

Go to the fusebox, remove the top cover and the layer that holds the fuse board. Underneath hidden in the birds nest of wiring will be a round, black, single pin plug, with what what looks like a braided cable going into one side. That is the connection from the pump harness to the engine harness, make sure that it is properly connected and not corroded.

 

[tone capone]

That is indeed the central locking harness.

Go to the fusebox, remove the top cover and the layer that holds the fuse board. Underneath hidden in the birds nest of wiring will be a round, black, single pin plug, with what what looks like a braided cable going into one side. That is the connection from the pump harness to the engine harness, make sure that it is properly connected and not corroded.

 

[tone capone]

Thanks. Appreciated.