FUEL SWIRLPOT - The Volvo 240 fuel tank has a good design to keep fuel pooled around the internal fuel pump, fine for nearly all uses. However, around a racetrack typically on a very hard left hand corner combined with a low fuel level, the 'In-Tank pump' can momentarily pickup air, and the air feeds into the main pump and an instant pressure loss occurs at the injectors, followed by fuel leanout and engine hesitation - not good !

ACTION - an external fuel swirl pot will solve this problem - an extra reservoir of fuel that sits between the pre pump and main pump. Using the 740 in-tank pump detailed below, the pot should keep itself well primed, hence no real need to have the return injector rail line feed into the pot as well, just leave it alone to return normally back to the fuel tank.
Without a swirlpot, the only way to avoid a potential drop in fuel pressure on hard left hand corners is to have the tank well-over 1/3 full.

This small swirlpot capacity is approximately 0.8 litre or 0.2 US gal. MOUNTING - The swirlpot can be mounted for example high in the free space situated between the front left corner of the rounded fuel tank and the panhard bar mounting bracket. The left side main chassis rail protects it from the side. The unit lines up with existing fuel lines that route through the panhard bar mounting bracket, so no issues there. Safer outside than in the boot ? EFI Update - Interestingly, a leanout wasn't evident with the former mechanical K-Jet fuel injection, but it was after fitting Haltech EFI, (I did remove the K-Jet fuel accumulator that holds extra fuel volume). Probable fuel demand has increased with big EFI injectors, as lap times improved. I only confirmed the leanout during a track test day when I had time to observe my air / fuel ratio LED's. When mentioning this observed problem to a 242GT driver with a similar aftermarket EFI set-up, he too noticed the same lean-out issue with his vehicle at the same point on the circuit.

IN-TANK FUEL PUMP & MAIN PUMP INFO- Volvo 240 upgrade

Advice - In-Tank pump (or Pre-Pump): I advise all 240 T owners to upgrade to the 740 / 780 / 940 Turbo higher tech in-tank pump #VO-3517845 (plus you need the new bracket #VO-1312390). As the 740 pump is about 1" 25 mm longer in length, you need to trim (hacksaw) about 25 mm off the long steel feed tube before fitting the joiner hose. Basically you make the new pump sit at the same bottom length as the original. Depending on year, you may need to affix a longer earth wire. 2x Nuts for 740 pump wires are an odd M 3.5 mm (some electronics bits use this thread) (old 240 pumps are 6/32" or M 4 mm).

Advice - Main pump: #VO-9142045 740/940 TURBO (B23FT,B230FT) to 960 models.
If upgrading a 240 pump & still usung K-Jet injection, you will need to obtain & fit some adaptors to connect to the fuel accumulator.

In Tank pumps LEFT - RIGHT

Click pic to enlarge LEFT Pic - shows two newer style pump (old ones are shorter and all plastic), but the left one has the wrong locating mount - the pumps weight is being held by the rubber hose and clamp above. RIGHT Pic - 740 / 780 / 940 Turbo 2.3L (B230FT) higher tech in-tank pump #VO-3517845 (other number marked on pump is 6443270) Importantly the pic shows the correct bracket #VO-1312390 where the pump sits in the bracket against an edge (rather than falling thru like the one on the left). Reportably 0.8 Bar = 11.6 psi  Pre-Pump filter 240 to 940 #VO-1274817

LEFT - RIGHT

Click pic to enlarge LEFT Pic - standard type of pump, chunky plastic vanes. Fuel Outlet is restricted to approx 2.5 mm dia, to create some pressure. RIGHT Pic - Volvo #VO-3517845 higher tech unit with trick metal vanes - notice 'AC' letters, (but numbers don't match AC Delco lists). Also small hole for over pressure? and debris relief. Fuel Outlet is full flow 5.7 mm dia.

Issues people have: 240 K-Jet Mechanical Fuel Injection (NOT EFI): Volvo Hose connections at the Fuel tank Sender unit
The rubber Outlet hose simply undoes with a clamp - its a low pressure feed from the in-tank fuel pump.

Return line - Even at full throttle a significant percentage of fuel is returned back to the tank. The Return line is an aircraft style nylon tube pushed over a barb fitting - you won't get this off at the sender! To get this line undone and the sender unit out, you need to get under the car and undo a compression fitting for the return fuel line (located above the diff). Simply if its never been undone before, the compression fitting is torture to undo for the first time, and you will need long series spanners for mechanical advantage.
If you cut the nylon return line in desperation this is how to reaffix - not in situ - when its out of the car on the bench! If you heat the fitting somewhat with a heat gun the tube will push on firmly and squeeze around the barb, don't heat the hose. Same technique for 5mm? fuel lines on the fuel distributor.

Fuel accumulator overflow - older models have a rubber line going back to the tank. 1985 era models have a fuel accumulator that eliminates this tube and has a small screw with slots in case it leaks, a worthy upgrade. If you upgrade simply block off the line at the sender.