I have a 1987 740 non-turbo with 395,000 miles on it. I have recently been having a problem with the fuel pump circuit. The first symptom was slow starting after the car sat overnight. I would have ot crank it for a while. Since my wife began refusing to drive the car I began to troubleshoot it. This has altered the behavior somewhat.

There are two relays inside of the fuel pump relay. The main system relay is working fine, but the relay that powers the main fuel pump is not. When I turn on the ignition, the system relay energizes. When I turn the key further to engage the starter, the fuel relay remains open. When I stop cranking the engine, this relay closes for perhaps a second and I can hear the fuel pump under the car run until the circuit opens. Again, this only happens for approximately one second.

I have turned on the ignition and grounded the 86/2 pin, and the relay closes energizing the 87/2 pin and powering up the fuel pump.

I have been able to get the car to run by repeatedly running the pump for these 1 second intervals by turning the ignition switch on and off to let the pump run for the one second interval. I believe this is pressurizing the fuel rail. When I think I have pressurized the rail, I try cranking the engine, and sometimes it kicks in and runs. Obviously, when it is running the 86/2 pin is remaining grounded and the relay remains energized until I turn the engine off.

I realize there is a sensor in the distributor which needs to inform the ECU that the engine is turning for the system to work, but do not know if this would have any part given the symptoms. I have cleane up all the ground connections on the engine and by the ECU.

Here is the main question I have for anyone who knows:
As I said, the relay does not close when I am cranking the engine. I believe it should, but do not understand why might not. Well, yes the 86/2 pin is not getting grounded out, but why not? I also realize that this is going through the ECU. Does anyone understand this circuit? The confounding thing is that the circuit works once the engine is running, just not when it is cranking.

I apologize for the length, but I figure it will save a few questions.