Fuel injector won't allow gas to flow into engine, have spark, have fuel psi. All fuses ok. OBD connection won't connect to reader can't get codes.

lots of causes , injector leaks sure. is one of many.
this is EFI and EFI only controls injection.(and spark)

it and all its inputs. do. called sensors.
1998 car in usa the scan tool tells you what all sensors are doing,called PID scans and DTC errors of any kind
25 year old car. and engine and all parts on it.

ALL fuses good?
NEXT:
scan the PCM see P03xx error or others? (scan it)
p0171 And P0174? P03xx codes and more do the scans.
engine good first. for sure this OLD.
we do engine tests.
compression over 150psi on all 8 cylinders.????
vacuum gauge at 20" HG at idle and not BOUNCING
we use tools to find cause. gue$$ing can be endless and super expensive or worse adding on wrong parts.
SPARK:
8 spark plugs all new, and all 8 COP boots new
boots never every lasted, 25years, nor spark plugs
and last fueling , cant burn fuel correctly with bad engine or bad spark CAN not.

SENSORs and stuff:
MAF SENSOR BAD OR WEAK, OR NEVER CLEAN IN 25 YEARS WILL RUN LEAN .
FPR 25 YEARS OLD ARE BAD. THEY ALLOW FUEL PRESSURE TO BE CRAZY TOO HIGH OR LOW
CALLED OUT OF SPEC. (or gets stuck at max PSI)
THE VACUUM HOSE TO FPR MISSING FUEL PRESSURE WILL BE WAY WAY TOO HIGH and super RICH BURN.!
IF FPR VAC NIPPILLE IS LEAKING FUEL IT IS BAD.
Fuel Pressure Engine Running kPa (psi) (28-45)
Key On Engine Off kPa (psi) 35-45)
THIS SPECS ARE DECEIVING,
EFI LAWS, KEY ON PRESSURE IS ALWAYS HIGHEST PSI. (DUE TO ZERO VACUUM)
AND RUNNING ENG AND VACUUM MAX INCHES HG, IS LOWEST PSI FUEL;. IF NOT RUNS RICH AS A PIG.
KEY ON PRESSURE FPR IS 5 TO 6 PSI FUEL LOWER THAN AT IDLE. <THAT IS ITS A#1 TOP JOB THIS.

EXAMPLE 40 PSI KEYON PRESSURE.
THE IDLE WILL BE ABOUT 35.(20 "HG IDLE)
THE FPR DOES ALL THAT.
IF NOT ALL INJECTOR , OVER OR UNDER INJECT.
PERSONALLY I NEVER EVER TRUST ANY OLD FPR. I HAVE HAND VACUUM PUMP TO TEST IT FULLY. AND HAVE FOR 4DECADES.MID 1980S

INJECTOR LEAK DOWN TESTS FAIL OR INJECTOR BALANCE TEST FAILS ,TOLD IN SM= SERVICE MANUAL.
BASICS BAD: IS THIS:
THERMOSTAT BAD. OR MISSING, OR NOT AT 180F TO 200F TEMP STUCK AT 150F BAD BAD BAD.

ECT BAD, SHOWS 150F WHEN COOLANT IS 180F
CAUSING:SUPER RICH INJECTIONS.
SO PCM IS STUCK IN COLD STARTUP MODE FOR EVER AND BURNS FUEL LIKE MAD.

SURE O2 SENSORS DEAD OR EXH CRACKS NEAR BY THEM MAKES THEM LIE AND EFI GOES HOG WILD RICK. SURE.

WHY NOT SCAN THE PCM FIRST.
AND SEE WHAT IS WRONG FIRST.
SAVE TONS OF GUESSING

LAST AND NOT THE LEAST
YOU CAN SCAN ANY PCM AND SEE IF IT IS IN LIMPHOME MODE AND IF IS, IT BURNS FUEL LIKE CRAZY
AND SEE TOO ,CLOSE LOOP MODE IS DEAD
FULLY HOT ENGINE.
YOU CAN SEE LTFT EFI IS STUCK FULL RICH.
AND DTC ERRORS ,LOTS?
THIS IS NOT GUESS IT IS TESTING USES REAL TOOLS. TO FIND CAUSE.

sounds like a fuel delivery problem, have you had the OBD read ?the backfire could be a symptom of timing out or misfire so need to check a few things

This problem can be hard to track down , it could be caused by several thing's ! A bad check valve in the fuel pump letting fuel drain back into the tank , not keeping fuel line pressure up , a crankshaft position sensor can also cause this as well as an ignition control module !
Checks
Action
DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.
Preliminary
?€¢
Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .

?€¢
Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .

?€¢
Search for bulletins.

Sensor/System
?€¢
Test the engine coolant temperature (ECT) sensor for being shifted in value. Connect a scan tool. Compare the engine coolant temperature against the intake air temperature (IAT) on a cold engine. The ECT and IAT sensor values should be within ?± 3?°C (5?°F) of each other. If the ECT sensor is out of range with the IAT sensor, check the resistance of the ECT sensor. Refer to Temperature Versus Resistance for resistance specifications. Replace the ECT sensor if the resistance is not within the specification. If the sensor is within the specification, repair the ECT signal circuit for high resistance.

?€¢
Inspect the mass air flow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Important: The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine. Install the MAF in the proper direction. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

?€¢
Inspect the camshaft position (CMP) sensor for proper mounting and/or a bad connection. A long crank time occurs if the PCM does not receive a CMP signal.

Fuel System
?€¢
Inspect the fuel pump relay operation. The fuel pump should turn ON for 2 seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis .

?€¢
A faulty in-tank fuel pump check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis .

?€¢
Inspect both injector fuses for being open. An open injector fuse causes four injectors and four ignition coils not to operate. Replace the fuse. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground.

?€¢
Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .

?€¢
Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .

?€¢
Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
?€¢
Test both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.

?€¢
Inspect for proper ignition voltage output with J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis .

?€¢
Remove the spark plugs and check for the following:

-
Correct heat range

-
Wet plugs

-
Cracks

-
Wear

-
Improper gap

-
Burned electrodes

-
Heavy deposits

Refer to Spark Plug Inspection in Engine Electrical.
?€¢
Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to DTC P0172 or P0175 for diagnosis of the rich condition. Refer to Spark Plug Inspection in Engine Electrical for diagnosis of coolant or oil fouled spark plugs.

?€¢
Inspect for bare or shorted ignition wires.

?€¢
Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

If you ran out of gas there is a very good chance that the fuel pump relay has blown a fuse or requires a reset. Fuses and relays are in the main fuse box behind battery. When you turn your ignition on to the one setting before the starter engages you should be able to hear the fuel pump running. If it does not then check those fuses. If it does run then there is a good chance that the crank shaft positioning sensor needs replacement.

Misfires are caused by one of 3 things-gas, spark, or compression-one of those is the problem. For gas, check the fuel pressure and see if it is at the right pressure for your car. Low fuel pressure will cause misfires. If pressure is good, it could still be an injector problem, like a clogged injector. If low pressure, suspect the fuel pump or the fuel filter.
For an ignition spark problem, check your spark plugs. Pull them out and inspect them for broken or cracked plugs, check the spark plug gap, check for oil fouled plugs. You may be able to isolate the misfire to a cylinder or two by the plugs condition. A misfiring plug or cylinder should show more black, sooty deposits than the other plugs. A normal firing plug will have a tan or brown colored insulator on the end with very little deposits. If the plugs are okay, clean them a bit if needed, and check for spark on the spark plug wire ends with engine cranking. Buy an inexpensive spark tester, or hold each spark plug wire metal end terminal 1/4 inch from a ground on the engine block, while cranking the engine. Wear a heavy glove to avoid getting shocked. Check that every cylinder is getting a strong blue spark to eliminate ignition as a problem. A weak, yellow or orange spark is an ignition problem, possibly a bad coil, or other ignition part.

If spark and gas is good, you may need to check engine compression. Any cylinder that has significantly lower compression than the other cylinders will cause a misfire, and set a misfire code. You should check for any trouble codes in the engine computer. A code reader or scanner would have to be connected to the diagnostic connector under the dash. What is "significantly lower" compression? About 15-20% less compression. Say you checked and had 150 psi compression in most cylinders. If one had 20% lower compression ( 150 X 20%= 30 psi, 150 -30 =120 psi, or same as saying 150 X 80%= 120 psi.), a condition like that can cause a misfire. I hope I have made sense here. Good luck, and post back what you find, or if any questions.

Try checking the "Main Relay" and its fuse.
Hope this helps.

A lot of solutions for this. It could be fuel pump, timing, crankshaft sensor,. Question? Was the check engine light on before it quit on you? Hmmmm. If so we need to scan the codes to find out whats wrong. If not we need to find out if the problem is fuel related or electrical. How many miles on the vehicle? Good luck!!!!

OK three essentials for a running motor......

1. Fuel - Check to ensure you have gas up to the engine. Check fuel filter, fuel pump and fuel injectors.
2. Spark - Make sure your system has electrical current to fire the plugs. Check your wires to the coil(s) the plug wires, cap & rotor and spark plugs and gaps.
3. Air - Check to make sure any air flow sensors are connected, most cars wont run with the MAF (Mass air flow) sensor disabled. Check your air filter to make sure its not dirty. if it is it can restrict air flow and cause your motor to flood its self out instead of allowing the gas to ignite, hope you found my answer helpful!

Check the fuel pressure first. At the right top of the engine you'll find a connector like for the tire ( a bit more in diameter) Connect this with a pressure tester. You need 48 to 52 PSI, if you read out much more or less, replace the fuel filter unit (located over the rear axle, tow lines at right side, one line at left side). Inside the fuel filter is the pressure regulator. If the pressure is ok, please read out the trouble codes. Without a code reader: switch the ign.key to on, wait till the bulb test is over, than switch off-on four times. The miles will change to a "P.." with four digits. Write down the codes till you read "done". If you read only "done" there are not TC's are stored. Come back after testing this

Flel regulator will only affect max fuel pressure only will not cause it to not start. try replacing fuel filter first if still does not get fuel then you need to see if it is fuel related or if you have a spark at the spark plugs, pull off a spark plug boot and put screw driver in it hold 1/4 inch away from bare metal and crank engine if you get a spark then it's fuel relateed if no fuel it can be the crank shaft sensor or the cam shaft sensor. let me know if it has fire.