Possible fuel pump problem?

[Pooky]

I ran my W210 E320 (79,000 miles) out of fuel for the first time last week (was idling the engine to warm the car up and it just died) As my E300 TD fuel gauge would completely bottom out before running out of fuel I didn’t immediately consider fuel starvation so spent a good couple of minutes intermittently trying to start the car. Eventually I stuck five litres of diesel in the tank and after a further good couple of minutes cranking, the engine finally sprang into life.

All very well, I hear you say but since then cold or hot, the engine has required a good 1-2 seconds of cranking to start whereas previously you didn’t hear it cranking, it would burst straight into life as soon as the key hit position III.

I am now wondering whether the prolonged cranking on an empty tank has somehow damaged the rear fuel pump by drawing air into it. I believe that these pumps rely on diesel as a lubricant. It could be air still in the lines somewhere, but I think this unlikely as the car has run for over an hour and about forty miles since being restarted and when kicked down, it still pulls strongly without any hesitation.

Any thoughts? I know a lot of cars will crank a little before starting but this one has never not started instantly, even at -12*C on a depleted battery so something has happened.

 

[Steve@Avantgarde]

I doubt it, but you have probably got an injector leaking off too much hence the longer crank.

Try some injector cleaner as a fuel additive as well as a capful of 2 stroke oil in the fuel and see what it does.

 

[mioba]

could it be the fuel filter picked up the rubbish left in the tank

 

[Steve@Avantgarde]

Could be that as well

 

[Pooky]

Thanks for the replies, guys.

I did consider the injectors but this happened only after running the tank dry. I assume that an injector fault would appear gradually rather than overnight. I have been running the car with Hydra cetane booster which I believes cleans the injectors as well as boosting the cetane number.

I too considered crap from the tank in the rear fuel filter. I don’t know how accurate the ‘range’ calculation is in the E320 but it was showing 1.8 gallons remaining when the engine cut out. To be honest I can’t remember whether the car was standing on level ground at the time so it feasibly could have had that amount remaining with the fuel pipe not submerged.

Does anyone know if that rear fuel filter can be reverse flushed? If so it might be worth a try before replacing the unit.

 

[mersum1es]

Can you see air bubbles in clear fuel lines?

 

[Pooky]

Can you see air bubbles in clear fuel lines?

None visible.

 

[mattkh]

Check the amount of water at the bottom of the filter in the engine compartment.

 

[joderest]

have to ask, what is it about two stroke oil being put into a diesel, what does it do ?

 

[mioba]

reverse flushing will only push any crud back to come back to the filter. Better replacing it if its never been done before.
Good point above regarding the fuel filter and water, some fuels filters have a drain on the bottom for this purpose.

 

[Pooky]

Check the amount of water at the bottom of the filter in the engine compartment.

Yes, I shall do that as a precaution.