So I have sprayed my carb with carb cleaner, check the fuel line (which fuel flows fine through) but it starts for a few seconds then dies no matter the position of the throttle. Any advice???

have the carby overhauled
water or junk in the main jet

Try spraying carb cleaner into the air intake tube for the throttle body as someone tries to start the engine. If it starts, runs for a few seconds and dies...its fuel related-most likely your fuel pump.
If it doesn't start at all while spraying carb clnr and attempting to start- most likely ignition/electrical problem Hope this helps you??

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There are a few things you can check for, 1. the idle air control valve for carbon and the same for the throttle plate having varnish or carbon build-up . Use spray carb. cleaner if any of these are black with carbon.2. A dirty mass air flow sensor will cause stalling and Idle problems . You can get cleaner just for mass air flow sensors ,don't use carb.clean ,or brake clean ! Or you could possibly have a vacuum leak ! check all vacuum hose , you can spray carb cleaner at intake gaskets to check for leaks , but be careful it is flammable !!!
Vacuum Leak Checking With Choke Cleaner COLD ENGINE look at this video

Check the fuel pressure to make sure the fuel pump is good

Issue with Gaz Line transportation.. Check input Gas Line... Take Off Gaz line from Carb Start engine see if gas came out if yes..Check your intake carb for Durt inside the line ...Also chek all your Vaccum Line and sensor Volvo are sensitive for Vaccum lost and The Carb need it ..Also if it Fuel injection... Check for Ignition Control Box for Malfunctioning Relay ...good luck

You will need to check to see if you are loosing spark or fuel pressure.You can try spraying the carb.cleaner or brake cleaner into the throttle body and if it starts for a few seconds then you know it is a fuel issue.If not check for spark and if no spark then it could be ignition module.Hope this helps.Good luck.

1) Faulty connection to the Idle Air Control ((IAC) valve or the passage ways to and from the valve in the throttle body have become gummed up and need a clean. You need to remove all air cleaner pipe work. Spray IAC apertures with carb. cleaning spray and wipe with kitchen towel or cloth. The apertures are ports on the interior side walls of the throttle body immediately before and after the throttle flap assembly. The IAC can be unbolted and cleaned pretty easily. 2) Fuel pump fuse, faulty fuel pump relay, faulty pump or locked fuel filter- can do a collective check of all of these by simply disconnecting the fuel line and seeing the amount and pressure of fuel flow when ignition key in second position.

TOOLS NEENED ......
FLATE BLADE SCREW DRIVER/STAR SCREW DRIVER/10MM/ QUARTER IN DRIVE RATCHET WITH 5 INCH EXTENTION/CARB. CLEANER OR INTAKE CLEANER/LAXTEX GLOVES./ TOOTH BRUSH
SPECIAL TOOLS REQUIRED ( AIR COMPRESSOR) WITH BLOW GUN
WEAR SAFETY GLASSES WHEN PERFORMING THIS TASK!!!!


START BY CHECKING ALL VAC. LINES/HOSES
MAKING SURE ALL IS CONNECTED.

IF ALL LINES LOOK AS IF THERE FITTED OK.
NEXT REMOVE AIR INDUCTION SYSTEM , THIS IS THE PARTS START
AT AIR FILTER BOX AND IS FITTED TO THROTTLE BODY.
REMOVE THIS PART( THERE WILL BE A WIRE GOING TO THIS PART(MASS AIR FLOW SENSOR) CARFULE NOT TO DAMAGE, UNCLIP WIRE GOING TO SENSOR.
NEXT LOOK IN SIDE THROTTLE BODY NOTICE THERE IS A BUTTERFLY TYPE PLATE.
YOU WILL NEED TO PROP. THIS PLATE OPEN , THIS IS DONE BY USING YOUR FINGER(CAREFUL NOT TO HURT YOUR SELF)
YOU CAN USE A SCREW DRIVER TO HOLD OPEN BUTTERFLY
MAKE SURE YOU DONT USE A POCKET SCREW DRIVER , YOU NOT WANT IT TO FALL IN THE INTAKE SYSTEM.
YOU MAY NOTICE THAT THERE IS A SMALL HOLE NEAR BUTTERFLY
TAKE CARB./INTAKE CLEANER AND SPRAY IN THROTTLE BODY/BUTTERFLY/SMALL HOLE.
TAKE SOFT TOOTH BRUSH AND LIGHTLY BRUSH AROUND BUTTER FLY AND AROUND MATING SURFACE OF BUTTERFLY, USE CLOTH TO CLEAN CARBON ( TRY TO GET THIS CLEAN AS YOU CAN , USE CARB. CLEANER.INTAKE CLEANER THREE OR MORE TIME.( ALSO SPRAY IN WELL VENTALATED AREA.
AFTER CLEANING REALLY WELL !!!!!
TAKE AIR LINE WITH BLOW GUN AND BLOW OUT THROTTLE BODY, MAKING SURE YOU GET ALL OF THE CLEANER/CARBON OUT.
ALSO BLOW IN SMALL HOLE( NOT DIRECTLY ON HOLE BUT NEAR HOLE.
NEXT STEP. IS TO PUT AIR INDUCTION HOSE BACK ON , MAKING SURE YOU PUT HOSE OVER THROTTLE BODY AND SECURING WITH FASTENER AS WELL AS OTHER END GOING TO AIR FILTER BOX.
RECONNECT ALL VAC. LINE/HOSE TO THERE ORIGNAL LOCATION
RECONNECT WIRE GOING TO MASS AIR FLOW

NOW TRY STARTING VEHICLE , MAY TAKE A FEW TIMES TO CLEAR
ALL THAT CLEANER THAT YOU SPRAY IN INTAKE.
IF RUN , YOU MADE A FIX!!!
IF STILL HAVE A PROBLEM MAY HAVE PROBLEMS WITH MASS AIR FLOW SENSOR.
GOOD LUCK!

Sounds like the fuel supply through is inadequate. That is a Want-to-be fuel injection system that uses a relay to enrichen the gas mixture.

Solution could be a container of fuel system cleaner, and a spray or two of carb cleaner in the injector.

Other causes could be:
Failure of the "choke" to richen the gas mixture
Vacuum line leakage.
Fuel filter becoming clogged

The mass air flow can cause these symptoms