Okay. First things first. The disclaimer. If you are uncomfortable diagnosing your car's ailment based on the symptoms you have received, you should probably take/TOW your car to a local shop to have it serviced/fixed to minimize the possibility you could cause further damage to your car.
The first time I had a fuel pump fail on me, I was driving to work and made a turn at a stop light and proceeded up a rather steep hill. As I was going up the hill, the e30 sputtered and the engine shutoff - on the right hand side of a busy road. Based on the symptoms (comparing them with a previous car I owned) and mileage, I was worried my timing belt broke and if I restarted the car, I was going to do engine damage. I'm a lot more confident now - and was more confident making a determination this time based on my environment (late for work vs. non-stressful), location (busy road vs. parking lot), symptoms, and ability to walk around the car and troubleshoot.
Symptoms - just an abbreviated list, based on my limited experience, feel free to chime in so I can update
Immediate loss of power while driving - irregardless of gas pedal position
When turning over the car, the car briefly idles low and rough before engine shuts off
The engine turns off after a few seconds while running
Process
Have to be able to get to or access the fuel pump.
In a 1990 325 iS (e30), the fuel pump is located inside the fuel tank; the top of the fuel pump is accessible underneath the rear seat.
Straddle the drive shaft hump and grab the bottom section of the rear seat where the seat meets the carpet/floor pan.
Pull upwards. You may need to apply a little bit of force to "pop" the rear seat off of the retention points.
The bottom of the rear seat might get in the way. Move the rear seat section; from the car, if possible. Resting it in your trunk is a possible option.
Pull back the underlayment to expose the access panels.
Then remove the access panel. I was actually able to use the screwdriver in my toolkit. Yay! BMW Factory Toolkit FTW!
I removed both panels in the e30 - I didn't have my Bentley Publishers manual and forgot where the fuel pump resided.
The fuel pump in this e30 is on the passenger side - I was really able to tell by the nozzle and fuel hose that left the top of the fuel pump.
FYI/FWIW - behind the drivers seat in this e30 is the fuel tank level sender.
The thought process here is to carefully and firmly, rap the top of the fuel pump in an attempt to get it to start running/pumping fuel in order to get you to your destination, a repair shop, or back home to get your car.
Be careful not to break any of the electrical connectors or fuel lines on top of the fuel pump!
I selected a quart-sized bottle of oil/ATF, but you could use a soft rubber mallet or your hand (be sure to wrap a cloth around your hand to protect it from sharp edges).
I know I took a good 10 minutes to size up the situation - looking at the orientation of the bottle, the angle of the strike, and estimate the amount of force to use... - just so I wouldn't mess up the connectors, lines, or pump.
So while sitting in the drivers seat with the passenger seat forward, orient yourself so you can reach back and tap the top of the fuel pump with whatever object you selected while turning the key in the ignition.
Turn the key in the ignition to start the car (with your left hand), lean into the back seat, and rap the fuel pump with your selected object (using your right hand).
Turning the key to ON or START should supply power to the fuel pump. A firm tap may "assist" the motor and pump to "unstick" and commence pumping fuel.
With the key to START, I was able to get the fuel pump to start pumping fuel and my car immediately turned over and ran like a champ.
This roadside DIY fix/trick has been attempted and proven successful.
Good luck.
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