The OVP is a tricky bugger, often it will seem fine cold or sometimes warm, but it is a touchy git and will often be very very intermittent, I would consider a new fuel pump relay and an OVP, excpecially if it is original

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red