W116 450 SEL Fuel Starvation Problem

[EDZ649]

I seem to have a fuel starvation issue on the W116.

The car will start no problem, in fact it fires up first time. The cold start system seems to work fine and after a while the revs drop down to normal idle speed, albeit a very lump idle.

If I press the throttle the engine dies immediately, even if I press it very gently.

The car will start again straight away but dies as soon as I press the throttle again.

Any ideas guys?

 

[219]

Vacuum leak on the induction side ?

Blocked fuel filter ; faulty fuel pump ( IIRC dual pumps so one might be faulty ) or FPR ?

 

[grober]

Might be useful to monitor the fuel pressure- usually a take off point somewhere in the plumbing? Symptoms do sound like fuel starvation.

 

[jonnyboy]

Does it have a metering head and airflow meter? May be worth whipping off the airfilter and cleaning everything up. If its stood for a while it could just be crap petrol pulling its way through. Dont use injector cleaner or you'll end up with loads of crap going through the system.

 

[grober]

On older INJECTION systems like these my first port of call is the Warm up regulator A bimetal strip+heater/ little control springs/ a vacuum diaphragm/ vacuum connections and pipe work- all things liable to fall over with age. Easiest test is a straight swap with a proven working one.

 

[219]

I had exactly these symptoms with a 190E - turned out to be a vacuum pipe that had come off on the induction side of the engine - under the air filter - clue was the hissing sound that could be heard under the bonnet when the engine was idling - fortunately the pipe just needed put back in place and problem never recurred .

On the W116 , it is entirely possible that some rubber part may have perished and cracked - worth cocking an ear under the bonnet at tickover and listening for any vacuum leaks . Just a thought - any disconnected vacuum pipes round about the removed wing ? Is central locking working OK - that system is entirely driven by engine vacuum using accumulator spheres (like the ones visible where the wing has been removed , are they cracked ? ) and one way valves - a fault here could affect the engine running .

 

[EDZ649]

Thank you guys, my first thought was the fuel pressure regulator but Olly mentioned yesterday that some of the rubber parts could have failed. Will have a play and see what transpires!