Volvo 1986 760 turbo fuel injection

What year is the vehicle? Mitsubishi used two different systems on that engine. Before 2006 they used a Fuel Injection Pump and after 2006 they used a Common Rail system.
An injection pump is a mechanical setup that is driven by the timing belt to make sure it matches the engine speed when driving.
A common rail system uses an electronic signal to fire each injector at the correct moment from a shared fuel supply rail on the engine.
In general the injector firing order needs to match the mechanical firing order of the engine so the fuel is injected into the correct cylinder at the correct moment. The Firing order is 1, 3, 4, 2. Number 1 is nearest the engine belts and pulleys.

This is what it looks like

faulty injectors or faulty injector control
loss of power is fuel problems ( pump or injectors )
loss of turbo boost is lack of extra fire from the combustion --back to injector or control and bad idling is injectors squirting/ not squirting and not atomizing properly

What fuel injection system does it have ? Center port fuel injection or fuel rail injection ? Are the injectors being controlled (turned on) by the PCM - engine computer ? Do you know how to test injector drives ? Injector driver is a transistor inside the PCM , that controls the on/off time of the injectors . How to test fuel injector circuit with basic tools open control wire How to change SPIDER INJECTOR on Chevrolet V8

It is impossible to answer your question without knowing the YEAR, MAKE, and MODEL of your vehicle.
That being said, either the fuel injection controller has failed, or there is a problem with the wire leading to the injector, or there is an obstruction in the fuel rail preventing fuel from reaching the injector. Use an circuit tester to see if the injector is regularly receiving a pulse. If it is not, you have a wiring issue or a bad ICU. If it is getting a regular pulse, you have an obstruction in the rail (or you still have a clogged injector).

It should be on the end of the Fuel Rail feeding the Injectors.

this is USA forum, and we dont have this car.
IT'S NOT A USA 2002 DIESEL trooper.
that and exact engine, size.
we have, 3 gas engines, 2.2L,3.2. and 3.5L
here. only and books that cover only those 3 engines.
so if a diesel dies.
what>?
check fuses.
scan it.
check filters
try test fuel to see if it runs on test fuel
test the glow plugs yet,?

if pump pressure is dead,?
check, power to the pump yet? (fuses are first)

there are 4,.6 and 8cyl. diesels by Isuzu.,
which is it>
they have names.
7 diffr. B engines, 3,xxxx liters.
and
5 diffr. 4Jxx series engines.
my guess is the engine is.
3.0 L 4JX1 TD I4
3.1 L 4JG2 TD I4

wiki says.
"
European and Asian buyers could opt for the diesel engine option of the 4JG2 3.1-liter (later superseded by the more problematic 4JX1 3.0-liter of 159 PS or 117 kW)
4jg2 is indirect injected
4jX1 is direct.
apples and orange diffr.! injection classes. '

learn what's under that hood, then fix it?

what country
what engine, real names, not 3L vague-ness. please.

no, fuel injectors are on the motor, in you look at your engine, right above one of the spark plugs, you will see an silver looking bar go accross twords the next plug, this is you fuel rail, on the inside of this rail are the injectors, each one goes into the block and has two little wires going into it. Once you know which of these injectors is bad you can take off the fuel rail (being careful to relieve the fuel pressure first) and then replace the injector, which snaps into both the block and the fuel rail, please also note that when you do this, be sure the old "o" rings come out with the old inject and the new injectors have the "o" ring in place, i once had a bad experience whyen i neglected to do so. Good Luck!

electric problem there must be a loose connection,the wires for the solenoid on the fuel rail ,the solenoid is not opening at the right time ,see for the electric connection,when replacing head gasket,may be you have not plug the wire connection

There should always be power at the injectors as long as the fuel pump is on. The fuel injection ECU provides a ground to the injectors to turn them on.
You most likely have a bad fuel injection ECU. This is a very common failure on 88,89 and 90 SAABs.