Where is thw fuel injection relay for a 91 beretta 3.1

There is no relay for the injectors. Fuses 54 & 55 in the IDPM supply power to the injectors with the ignition switch in the on or start position, the ECM - engine computer turns them on by supplying a ground in a pulse width modulation .

SYSTEM DESCRIPTION The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the ECM memory. The program value is preset by engine operating conditions. These conditions are determined by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air flow sensor.

Definition of Fuel Injector Pulse Width (liveabout.com)

Have you checked your compression? An engine needs 3 things to run, air/fuel, spark, & compression happening at the correct time.

your testing is no good. (no engine told at all)
the ECM ,only injects using this logic.,

1: fuses good
2: ECM good (i bet yes)
3: CKP and CMP senors dead.
4: if the ECM sees spark dead it cuts all fuel to prevent as seen on TV "CRASH AND BURN" and by LAWs on this fact.
5: some cars have Injector buffer modules between ECM and injector rails.(LOOK OR READ THE FSM)
6: fuel pump dead.
7: fuel filters clogged or it and injectors too (they have 10micron screens)
8: have a NOID light? to see if injectors are not fired by ECM?
the injector plugs all have 12vdc on one pin, do they if not fuse blowN, #1 AGAIN.. USING A DMM, METER.

mostly this list works too BELOW.. (noid lamp fails)
fuses
ckp and or CMP sensor dead. The crank and cam must spin !!!!
if CMP is dead and cam does not spin, well that be cam drive dead.

spark dead, if spark is dead ECM detects it dead and fueling is banned,(blocked)by laws. (fire avoided , win)
way3:
if NOID passes on all injectors (as will spark tests)
fuel pressure gone. we measure it. (bad pump, clogs or bad fuel)

if spark is good test fuel test works.
ever do test fuel on any engine using can-o-fuel or instant start fuel in a spray can, seen engine run for 3 seconds and sounds good.?
RTM FIRST? there are sure more causes, list is common, only. and hard logic truths.

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helps to know what type of car. check body ground. if car was jumped with reverse polarity, can cause a wide variety of problems. it controls all parts of run. it uses senser data to adjust for best performance. water or fire damage can cause one or more items to not work in ECU. ICM is on distributor it controls fire, no fire ECU will not allow fuel injectors to open and close . this also can be injector relay . remember if ECM is not bad the relays it controls may be bad. one bade relay or senser can stop ECM, it is computer that is set to shut down if there is a problem with circuit, good luck. please let me know what the problem was if you get it fixed.

check your crank poistioning sensor.is it fuel injected?if it is fuel injected check for injector signal which will tell you thatyour ECM is getting crank poistioning signal and distributer signal,check fuses if there is no signal, bad injector

when carb is wide open ????? No carb ,fuel injection ???? Are the injectors being controlled by the PCM / ECM ??? Have replaced fuel pump, fuel filter and fuel pump relay.???? Did you test first ?

sounds like u got no injector pulse comin from ecm.we need to pull ecm codes an review them ,possible camshaft sensors faulty they usually provide reference pulses to ecm for injector firing or pulse.without this pulse ur injectors will never open up to let fuel enter combustion chamber. one way of checking pulse is to connect a noid light(small light bulb that plugs in injector pigtail to chek for power to injector and ur pulsing ground coming from ecm to injector) an test for a blinking light while cranking engine.

1st relay on fire wall next to brake booster

Have you checked for injector pulse with a noid light at the injector connector? You could have a bad ecm.

Look for a bad fuse or relay. If both check out, most likely an ECM problem