This afternoon I changed the fuel filter for the hell of it and I cranked it over and it fired up as soon as the lines re-primed, and it ran pretty rough for about 5 seconds and then it died. I tried it a few more times and if I would open and close the throttle repeatedly it would rev up higher than idle, but it wouldn't hold and it would eventually choke out every time. Then I unplugged the tps and it fired right up and will idle forever, but at about 300-500 rpms and as soon as I try to open the throttle it dies (again, with the tps unplugged). While it's idling with the tps unplugged, if I plug the tps back in it either dies right away, or sputters and then dies.

What could it be?

 

Well, I put in a new fuel pump and it runs great now.....
Except for now the fuel gauge reads bone dry all the time.......
I must've done something wrong....
Well, it's a small price to pay for having a functional car!

 

Wasn't that one of the 1st things that you checked?

 

It is one of the first things I checked (when I had a whole day to mess around with the car because it left me stranded at my house...), BUT obviously it wasn't putting out enough pressure. It was cycling the pump, and the pump WAS still running, but it must've only been putting out marginal pressure, which would explain why it would run with the tps unplugged and not run with it plugged in (too low on pressure to even run above 300-500 rpms). It was filling my jar when I pressurized it, and when I pulled lines apart it would fill the jar when I cranked it, but it must've been not enough. I wish this thing would've had a schrader valve and I would've saved money on the cps.

What did I do wrong will the sending unit? I pulled it out and I put it back in...I didn't change anything except the pump. Stupid thing must be stuck or something....

 

Anyone know why the sending unit would work prior to removing the fuel pump, and then not afterward? I tipped the unit up and down a couple times and the float went up and down, but I didn't think that would kill it or make it come unattached from the arm or whatever holds it in the tube.

 

The sending unit is a variable resistor . The float and arm are pretty sensitive so if you banged or twisted something you have damaged the assembly. You will need to remove it again and check it out electrically. You may need to replace it.

 

There wasn't an arm with a float like I was used to seeing. It was all self contained in a tube. This is the oddball system that parts are ungodly expensive for , or the regina system....

 

I have a 1991 740 sedan with the Regina system. I'm not sure which one you have. If the crank position sensor is good and it's getting fuel it should start and run. What happened to mine is that the connector at the radio suppression relay went bad. This caused the car to stall and not restart. The radio suppression relay is in front of the coolant overflow tank on the passenger side wheel well. The relay is really just an injector relay to complete the power loop for the injectors. The connectors in the connector block go bad and it becomes intermittent. This is just one thing to check. You may want to run the car with a fuel pressure gauge on the fuel rail to see what happens to the fuel pressure when it stalls.