1991 Chevrolet caprice turns over but will not start, fuse OK, relay OK, no spark, no fuel to injectors. Trying to replace coil, can't get bolts out..

Make sure the battery has a full charge and battery connections all good. Have a helper crank it while you check for spark at the plugs. Also, use a fuel pressure gage and check proper fuel pressure. Check fuel injector pulse.
How long since a tune-up? Any applicable trouble codes?
I don't know what testing you have done?

It is a 20 amp inline fuse under the hood along the orange wire of the fuel pump relay. See middle of diagram below. The relay is mounted along the upper firewall.

Some conditions can cause the same problem:
1.- take out the tbi cover. now instruct some one to pass the key from off to acc and try to star. If you can not see the injector flushing a small amount of gasoline in this moment, the module inside the distributor is damaged or the computer fuse is blow out. this fuse is near the rear left corner of the hood, near fuel pump and A/C relays. if all is ok, go to number 2
2.- check connectors back distributor, both of them must be thight. now uuplug any cable of the sparks, put a screwdriver with a good insulted handle inside and place it near a ground point in such way that the metal of the screwdriver be at 1cm of the ground. Now make someone try to star engine. you must see a spark jumping to ground after no more tha 4 seconds after try to star. If you can not see it most probably coil is bad. If you can see it, fuel pump is the problem

Sounds like you spent a small fortune on fuel pumps. Don't keep trying to jump it to start. Take the battery off and have it charged up. No further tests will be valid without a fully charged battery.
Is it the computer? Always a possibility, but that should be your l;ast resort. You might change it and later find out it was a bad fuel pump relay, or something like that.
Lets go back to the point you put gas in and it fired off. ( Further cranking after that may have run the battery low enough that you lost spark.) A mechanic would next check if power was getting to the pump by checking the pump wire for power at the tank connector, when the engine was cranking over. If no power, pull fuel pump relay and check for available power on one terminal where relay plugs in. If power is ar the relay, swap relays and see if was a bad relay. If no help, further electrical tests need done before condemning the computer, wiring needs checked, grounds need checked, and the relay itself has one terminal that goes to ground. You be better off diagnosing the problem, or having it done, rather than throwing new parts at it. Try to get the pump working first, then if still won't start, check the injectors and injector circuit. And go back to check for spark-at this point having removed and replaced what you have, and jumping it, and cranking, cranking, cranking-if no spark, start by checking all fuses on the car.


Not much help, I know, but proper testing is the only way to find it.. Or just go ahead and change everything till you find it or are broke. Not being snippy, if I can help anymore, post back.

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Car not starting or turning over indicates towards multiple possibilities. It can be issue with battery or weak battery. But if battery checks out ok, then it can be starter issue or faulty alternator or problem with low fuel pressure or no spark at spark plugs due to dirty spark plugs or faulty ignition coil or injectors getting cracked or dirty and needs to be cleaned.

To confirm the problem, the basic troubleshooting is required.

Click this link below and follow the troubleshooting:------

http://technoanswers.blogspot.in/2012/02/car-starting-issues.html

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This will help.

Thanks.

either the wiring between the injector and the computer is bad, or the computer is bad. (ecm) the RED wire on both injectors should have 12V. connect a test light to the positive of the battery, now connect the tip to the DARK GREEN wire or the DARK BLUE wire on the injectors. you should get a rythmic flicker at the light when cranking the engine.. if both wires flicker, the injector thats not flowing fuel could be bad. if 1 does not flicker, check the wire to the computer, those wires go directly to the computer, no connectors. if the wiring is good, I suspect the computer is bad.

A car that cranks over but doesn't start, in many cases will be due to a bad fuel pump, a broken timing belt, an inoperative cam sensor or crank sensor. Also these problems are related to faulty spark plug. Check the spark at spark plugs when you start the car. Do you notice any spark. Actually you should see. If in case there is no spark then it's a spark plug problem. Also the coil pack gives power to spark plug. So check the voltage at coil pack. It will show 12 volt. If there is no voltage noticed at coil pack then its faulty coil pack that has to be replaced. If all the possible options checked out ok then check the car starter. The starter gets power from battery to start the car. If the starter is faulty then it will not let the car to start. Also check and confirm that there is fuel in the car. If its very low fuel then in some cases this causes the problem. Also check and confirm that fuel pump is functioning properly and the fuel filter is not clogged. One of the easiest ways to check for a fuel pump related problem is to spray a little starting fluid into the air intake while trying to start the car. If the car starts momentarily, then there's a good chance the fuel pump is not working or the car is out of gas. You can also listen for the fuel pump's humming sound when the key is first turned on. Also if a inoperative fuel pump is suspected, a good technician will always check to verify there is power and ground being supplied to the pump, to eliminate the possibility of a bad relay or electrical issue. Fuel pressure can be checked with a pressure gauge and if there is pressure, pulse can be checked at the fuel injectors in several ways including the most common, with the use of noid lights. If the injectors don't have pulse the engine won't start. ---------- This troubleshooting tips will help you to solve the problem. Thanks. Helpmech.

No you didn't hurt any thing,
You should have the Distributer cap, rotor,
and coil checked. to make sure you can get proper
spark.

BAD OIL PRESSURE SENSOR BAD CONNECTION BETWEEN COMPUTER AND INJECTORS, BAD INJECTORS

About a year or so ago, my 1991 240 Volvo was experiencing similar symptoms. Has this been an intermittent problem? (Sometimes starts, sometimes not?)
I looked at my fuses, especially fuse #6 which powers my fuel injector relay. With a friend, who is a professional mechanic, we determined fuel was getting to the injectors, but my coil spark was weak and injectors were not being pulsed. I wasted 300 dollars having the injector relay replaced, by another mechanic. Two weeks later, my car failed once again to start! It turned out to be a pitted connection at fuse #6! I inially just looked at the fuses, which were not blown, but when I took #6 out, it and the associated connector were pitted. Burnishing the connector and replacing #6 fuse has corrected this issue! If you haven't, pull your fuses, and inspect and clean the contacts! Maybe it's just that simple. Good Luck!!