SL55 Starting problem

[karozza]

After a nice run yesterday, I started the engine to go out for lunch & started hearing a kind of thumping noise (not too loud) from the back! Got out, opened the boot & it felt like it was coming from underneath the passenger side boot area; maybe like a loose exhaust mount!?.

Anyways, just over a half mile down the road, the noise went away & all was well; car drives normally & no warning messages in the dash.

But, after lunch, the car did not start as usual; it normally bursts into life just as the starter kicks in. This time, the starter turned quite a few times before it fired up. Then got home, after a while in the garage, gave it another try & the starter kept turning but the car did not start & then the starter stopped on it's own, tried again & fired up straight away.

Just tried starting again right now & fired up in the usual beautiful manner.

No warning messages; all as usual.

Any ideas??

 

[def90cars]

Fuel pump?

 

[karozza]

Fuel pump?

How come?? Would the pump making thumping noises??

 

[karozza]

So, no other suggestions??

 

[Auto-mobile]

How did it drive? You have 2 fuel pumps in the tank.

 

[BlackC55]

There is just one pump above the diff on am SL

 

[Auto-mobile]

I thought there was a secondary pump in the tank, built in.

 

[Dash1]

I thought there was a secondary pump in the tank, built in.

Hello Auto-mobile,

There are two pumps, primary and secondary, however, the one in the tank (secondary - little or no pressure) only serves to replenish the splash bowl only and to keep it full when cornering so the system does not draw in air. The main fuel pump, (primary - high pressure) also known as the delivery pump is actually underneath the car where Olly stated and supplies fuel to the fuel rail only.

The one in the tank, labelled as M3/1, from the diagram which you provided, cannot be repaired and if found to be faulty then I’m afraid the whole tank unit assembly has to be replaced, which is a very very expensive repair. With respect, it’s very easy to test them, but you being a mechanic should know how to go about this anyway. Any modern engineered fuel system operates on this principle now, granted, some vehicles do have the high-pressure pump also in the tank, but not the SL- R230 model.

Regards,

[FONT=&quot]Dash1[/FONT]

 

[karozza]

How did it drive? You have 2 fuel pumps in the tank.

The car drove in it's usual manner.

 

[Auto-mobile]

Going back 10 years now I think, I had recollections of changing one of those pumps, maybe it was for fuel starvation when cornering then causing a flat spot.

 

[Alps]

crank position sensor? cheapest thing firt? also worth getting it on start

 

[BlackC55]

There is a sensor adjacent to the pump. It causes this exact symptom.

Iirc it comes as part of the pump above the diff.

 

[Dash1]

There is a sensor adjacent to the pump. It causes this exact symptom.

Iirc it comes as part of the pump above the diff.

Hi Olly,

The fuel pump driver module is directly adjacent to the pump, is this the one you refer to, see attached photo below.

Regards,

[FONT=&quot]Dash1


[/FONT]

 

[BlackC55]

That's it.

 

[BlackC55]

I've just checked. It available as a separate part.

 

[BlackC55]

It's a ****ter to change.

 

[Dash1]

It's a ****ter to change.

I’ve never changed one Olly, but I’ll take your word for it, that’s good enough for me.

Regards,

[FONT=&quot]Dash1[/FONT]

 

[karozza]

Ok guys, shall I wait for this to happen again, or can I check if it's faulty on STAR??

 

[karozza]

I'm trying to establish if it does it on cold or warm start ups. Off to check it on STAR this week if I get the chance..