My 1993 940 Stalled on Freeway, Won't Re-start

[Big Bruce]

So far, a mobile mechanic has diagnosed bad fuel pump, and replaced the high-pressure pump and fuel filter. He also found that there was not a consistent delivery of volts to the spark plugs, so has replaced distributor cap, rotor, and ignition cables. Nothing wrong with air cleaner. The engine still will not start, but as it has done since the initial break-down, it cranks, occasionally "catches" but quickly goes back to cranking, and will not start. I sure would appreciate additional ideas from anyone who'e ever experienced anything like this with their 740 or 940.

[shegarty]

before getting too far into repairs and more intensive diagnosis check the fuel pump relay - behind fuse panel under the radio area (you have need to remove the pocket under the radio to get at it) - should be the white relay on the far left - try jiggling this while cranking the car - doesn't sound very scientific but this is a recurring problem on my 740 of the same vintage - if it fires up there's your problem

if it doesn't fire remove the relay and check the wiring to and the fit into the socket, this can become loose over time with the heating/cooling cycle - if this appears okay try replacing it with a known good one - there are some excellent write ups on the FAQ section of the brickboard for this

i suggest check this first from experience and because it is an easy and inexpensive fix - many others have replaced $$$ worth of parts only to find out the problem was a defective relay - i keep several spares from the junkyard for this specific reason

[Big Bruce]

Thanks for the info and suggestions. We will follow up on all of these, and I'll repost again with the results, hopefully positive ones.