Robert,

Sounds like you’re going to be busy.

Have also had the passenger carpet up and checked out the varying signal from the O2 sensor which I too took to mean all was okay there.

Like you my fuel pump relay is within the MAS. Just checked on the 'AllDataDiy' site and it is pin #14 of the X11/4 plug. The only codes that look like they might apply are:

2 – ‘fuel pump relay not functioning’
15 – ‘short circuit detected in fuel pump circuit’

Did check pin #14 on mine straight after the last incident but no codes where found. Also checked #3 (CIS-E) which showed no codes, and #8 (EZL) which did give code 17 (crankshaft position sensor defective (L5) ). Tend to ignore this code 17 though as 6 months ago I had the thing replaced (cost £150+) and it made no difference, also through this forum was subsequently advised that the recurrence of this code is a known problem and not to worry about…..

While at AllDataDiy I was just reading up about the location/workings of the fuel pump when I came across a MBZ Technical Service Bulletin entitled “Engine hesitates, cuts-out or is difficult to start at times” (#N7, AF07.32-U-3701A, issued on 05/05/97). This is the link:

http://www.alldatadiy.com/alldata/AFI~V4623745~C10264~R0~OD~N/0/34870055/56621118/56621127/56621128/34853741/34857029/34858641/34859192/34859264/82240627

but you probably need a login to really see what it says. Amongst other things this bulletin does mention are:

o All gasoline engines with rpm controlled fuel pump relay – The engine rpm signal (circuit TD) to the fuel pump relay may be short-circuited to ground or otherwise disturbed by one of the following components which utilise this signal: A/C compressor unit; Fuel pump replay; CIS-E control unit; Idle speed control unit; Tachometer.

o Further possible causes (CIS-E related): Loose ground terminal screw at intake manifold; Loose connectors for CIS-E wiring harness; Loose connectors (ground) in trunk for fuel pump; Loose connection at plug (X36) of fuel pump wiring harness.

Should get some time towards the end of this week to look at some of these things. As always, keep the correspondence coming.

Best regards,
Neil