1991 cadillac will not stay started

I can think of a couple of things that may be the problem.
1. Reset the computer by removing the + and - battery cables, leaving them off about 5 minutes. Reset the cables & start the car. Sometimes they get out of computer sequence and have problems.
2. If you ran the tank too low prior to filling up, you may have some trash in the line caught in the filter.
I wouldn't consider the fuel pump, because when it fails you cannot start the vehicle at all.
Does your check engine light stay on? Does it run rough while driving, or do you just have trouble getting it to start? If it runs rough, it could be spark plugs or the control sensors on each spark plug.

If you have good spark at the plugs then it is vacuum or fuel.
1 vac listen for hiss in the few min it runs
check lines for damage, splits, unhooked etc. don't forget under car and dash

2 check fuel pressure, check for fuel delivery to the cyl. remove spark plug crank and check small look for fuel. remove coil wire so it won't start on you.

MIKe

what about checking the injectors for operation , dirty or wiring problems

- When was the last time this car had a tune-up? Could be as simple as that. New spark plugs/rotor/distributor cap/condenser might do the trick.

Other causes could be:
- bad fuel pump relay (definitely first on the list of things to check, and cheapest to fix)
- clogged/old fuel filter
- bad fuel pump

I would try running some fuel tests to see if pump is working.

Try changing the fuel filter and air filter.

we are trying to figure out how to change sparkplugs in a 2003 cadillac deville

Hey how is coil ?? could your coil wire be lose or broken

You may have bumped a wire or vacuum hose causing your problem. Look in the areas where the plugs and wires are and check all connections and hoses. Look for missing or damaged wires and hoses. Be sure your routing of plug wires is correct.

was it the correct fuel pump with the propper psi?
have you checked you wires to make sure none got crossed. are the spark plugs propperly gapped?