JoeHorner
Senior Member
- Joined
- Aug 21, 2022
- Messages
- 125
- Reaction score
- 141
- Your Mercedes
- 2003 W203 C270CDI Elegance
Having ironed out most of the issues with our C270CDI, the one remaining (and worsening) one was fuel draining back overnight leading to a routine of "starts, stalls, won't restart" practically every morning.
Had replaced the engine bay rubber pipes (visibly perishing), fuel filter, and (slightly mangled) pipe from filter to LP pump to no avail so, today, decided to try and trace where the leak was happening.
Obviously, a leak on the suction side tends not to give any obvious wetness But, with the help of some compressed air and a bottle of plumbing leak detector spray, isn't too hard to track down.
Disconnected the inlet to the filter and used some spare pipe to connect it to an air supply (airbrush compressor), then sprayed all joints with the detector spray.
A quick blast of air gave a definite hissing sound from down round the inlet for the HP pump and, sure enough, removing the vacuum pump for access showed telltale bubbling from the return pipe connection:
New O rings on the inlet and return pipes, bubbling and hissing are gone & fully expect it to start as it should in the morning
Now, I know that "just replace all the seals" is the normal advice but I REALLY prefer to have a clear diagnosis AND a clear confirmation of cure
Had replaced the engine bay rubber pipes (visibly perishing), fuel filter, and (slightly mangled) pipe from filter to LP pump to no avail so, today, decided to try and trace where the leak was happening.
Obviously, a leak on the suction side tends not to give any obvious wetness But, with the help of some compressed air and a bottle of plumbing leak detector spray, isn't too hard to track down.
Disconnected the inlet to the filter and used some spare pipe to connect it to an air supply (airbrush compressor), then sprayed all joints with the detector spray.
A quick blast of air gave a definite hissing sound from down round the inlet for the HP pump and, sure enough, removing the vacuum pump for access showed telltale bubbling from the return pipe connection:
New O rings on the inlet and return pipes, bubbling and hissing are gone & fully expect it to start as it should in the morning
Now, I know that "just replace all the seals" is the normal advice but I REALLY prefer to have a clear diagnosis AND a clear confirmation of cure
