Reverse gear & full steering lock= Engine cut out......

[superleggera]

My 95 E300D 24v has come back from the garage after having a bit of work done on the engine (vacuum pump and the gear that drives it failed) and all seems okay so far apart from when I pop it into reverse, with full steering lock on (basically when I'm reversing into my drive or a parking space) it just cuts out suddenly. Putting it into P or N allows it to start up again no problem.

I've noticed that one of the test procedures for setting idle speed is to put the steering on full lock- is there something that is affected by the steering mechanism and could this be related to my problem?

I've searched this forum and I can't see anything relevant so I've started a new thread, apologies if this has been covered already. The technician at the garage is aware of it but he didn't seem to know what might be causing it but told me to take it and see if it clears up by driving it around a bit so I've taken the car with the intention of taking it back if necessary etc.

Many thanks

 

[carat 3.6]

What speed is the engine idleing at?

 

[superleggera]

Engine idles at usual 650-700-ish, can't be exact because I can't measure RPMs etc.

 

[superleggera]

Correction, it idles at 750 when in P, and drops down to around 600-650 when in D or R. Interestingly, switching the rear window heater on prevents the engine from cutting out.

 

[corned]

This is an odd one. I can understand that the power steering system will require more power from the engine when applying full lock. And the more lock, the more load. But why it should stall is a bit of a mystery. The ECU should attempt to level out the rpm when additional loads are applied (like when the A/C clutch kicks in), so this should not defeat a closed-loop feedback system like that. Unless the power steering pump has some problem and suddenly pulls a huge additional load which is enough to stall the engine.

Is the power steering reservoir at the correct level? No leaks? Does the drive belt squeal on full lock?

That the rear demist (another huge additional load on the engine via the alternator) prevents this from happening is even more baffling. Unless the increased load from that is enough to get the ECU to set the idle throttle power (nothing to do with rpm) high enough to ride the sudden load increase from the power steering pump?

An odd one. Hope your man gets to the bottom of it.

 

[superleggera]

Thanks for the reply. The man at the Merc specialist has ordered a special tool that allows mega-accurate checking/setting of the pump timing. The pump has been removed and refitted several times while replacing the vacuum pump and driving cam/gear and he wants to eliminate this before he starts chasing this cut-out fault. It didn't do it before it went in so he's thinking that it's related to that. Very odd however that it only cuts out in reverse gear and NOT when the rear de-mister is on!!