Mercedes: mercedes 500 sec cutting out, mercedes 500 sec, mercedes benz 560sec

Question
have 89 5oo sec problem was intermittent but now getting worse fuel pump relay dropping out replaced with new relay but no different bridge pins 7 and 8 and car runs have noticed idle speed can go high just before car cuts out as if idle speed control valve lost feed and returns to its rest position appears to be losing a common feed or earth to idle speed control and pump relay kickdown also becomes inoperative but understand it also controled through pump relay electronics any advice much appreciated

Answer
This sounds very close to a classic OVP relay failure.
Test battery and alternator.
A second possible issue is loss of tachometer signal = kills power to fuel pump.


PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1989 Mercedes Benz 560SEC
Part: Overload Relay
 Note:  
Aluminum cover with bracket : contains (2) 10 amp ATC fuses on top .     
 Year: 1988-
P2056-18126 Overload Relay Germany IN STOCK $75.80

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