Hi. Ive posted about this same problem before but can't find the old post and things seem to have changed anyway.

The situation: Starts normally, runs for 5 to 10 minutes than starts bucking and eventually stalls. I can restart it once or twice and it will run for 50 - 100 feet and then stalls again and will not start without working the throttle and cranking for a while. when I restart it this way it will idle rough and stall if I put it in Drive. Eventually the low idle will surge up to a about 1000 for a split second and then level off to 800 and I can drive the car for a short distance again. The other option is to let it sit for 5 - 10 minutes and it will again start and drive relatively normally for another 5 minutes.

What I've done: Changed the fuel filter, resoldered both fuel injection and Radio suppression relays. Ive shimmed the RSR contacts shut for testing with no change in behavior. The Tach works normally at all times (Does this eliminate the power stage as well as the hall sensor?).

I'm cash poor so please don't ask me to replace everything.

I'm guessing that I need to test for spark, injector pulse, and weather this is a lean or rich problem. What are the best ways for each.

P.S. I have been wondering where the aux fan relay is on this car I cannot find another relay in the engine compartment.

Sounds like you have a fuel delivery problem. Could be the regulator or pump.

Thanks. I'm leaning towards the pre-pump as the symptoms disappear when going down a slope and are accentuated while going up.

Checked the vacuum hose to the regulator and it was dry but had the odor of gas. The main fuel pump starts quietly and becomes noisy after a few seconds. I listened for the in-tank pump holding the flap open and could not hear anything but a slight gurgle or trickling sound.

Should I be hearing a distinct noise? Can I pull the main pump fuse and listen only for the in tank pump?

Can the main pump cause a gurgling sound via the return?

On a 740 wagon, how/where do I access the wires and lines that lead into the tank? Do I have to drop the tank?

I'll answer one of my own questions for future reader. I found the access panel beneath the section of carpeting between the rear seats and spare tire well. It is removed by removing the three bolts in slotted tabs that are beneath the sprung panels that cover the gap when the seats are folded. After removing those bolts the section can be slid forward and removed revealing a square panel with four bolts that covers the fuel tank.

Ok I just took it for a test drive and jumpered the contacts for the RSR just to be sure. No change. Perhaps I should mention that today is cool and humid and it started running poorly immediately. The only thing it does properly is idle.

I checked the vacuum line for the Fuel pressure regulator and it had the odor of gas but was dry.