I've been posting messages over the last few months for an intermittent cutoff problem with my 1990 740T. Thanks for all the great feedback. This appears to be a common problem with the series.

Because the engines shutoff has been so intermittent, and because brickboard members have found so many "cures" for the problem, it’s been very difficult to diagnose. I think I just got a break yesterday but I need to know more about the operation of the in-line fuel pump.

First the background and then the questions.

The problem is that the engine will occasionally shut off, most commonly at low speeds, typically when pulling out from a stop, but it does sometimes cut off at highway speed. I've been able to get off the road safely but it is definitely uncomfortable on the interstate. I wait a minute or two and the car starts right back up.

I and my local Volvo shop been throwing the kitchen sink at the thing. It's been in the shop 3 times and I've done even more work myself. The first replacement that made a difference was the in-tank fuel pump. The problem subsided but still came in occasionally. I did notice some burnt areas around the #1 fuse and replaced the fuse block, but no improvement.

I replaced the in-line fuel pump with one of these universal fits from Advance Auto, specifically a Master #E8002. This pump runs considerably louder than the one I took off, which annoyed me at first, but the noise may have provided the first real break.

I noticed from the noise that the pump was running continuously. While driving through a parking lot, I stopped to make a turn and heard the pump cut off. Two seconds later, the engine died. I turn the key to the on position two or 3 times before I heard the pump come on to prime the system. Once it came on, the car started no problem.

OK, the questions:

Is it normal for the in-line pump to run continuously?
If the fuel pump is designed to occasionally cut out under normal operation, what conditions cause it to cut out and restart?
What sensors feed the fuel pump relay?

BTW, I have not replaced the fuel pump relay yet (probably should have).

Thanks for your collective genius and help.