I make a big deal about having complete selection of parts with me when I travel in my old Volvos, but when we take Rose's 92-244 I'm lucky if I remember to take my wallet let alone spare parts. I was talking to Volvo Master Mechanic, Jason Leber about what he would take on a trip in a newer 240 (or 740) and his answer was most interesting. Take a engine speed sensor, a fuel pump relay, a voltage regulator/brush module for the alternator and a small jumper cable. Why these?
The rpm sensor stops the car if it fails and they do fail. Installation is a bit of a trick in the 240 as it is mounted to the top of the bell housing between the engine head and the firewall. It is held on with a 10mm hex headed bolt and is difficult to get at. He suggests a 1/4 drive 10mm socket and universal joint from the top or a 10 mm combination wrench accessing the bolt from the passenger side of the block when it has cooled off.
Worn brushes in the voltage regulator can also stop the car as the alternator stops charging and causes lots of strange symptoms as the battery fades. The module is replaceable with the alternator in the car but is much easier with the alternator removed.
If the fuel pump relay fails the fuel pump stops, and so do you. The relay is easy to replace and is mounted passenger footwell in the 240, accessible by removing the fibre panel under the dashboard below the glove box. The relay is white and is mounted on a clip between the fuel injection computer and the ignition computer. These relays fail because one of the 8 or so soldered connections inside lets go from old age and heat. Jason showed how the problem can be recognized and fixed at least temporarily. The relay has a manufacture date on it and our 240 has a relay from 1991. Apparently one that old is living on borrowed time. He took the plastic cover off the relay which exposes the back of a circuit board and 8 or so little mounds of solder. Close inspection of the solder showed circular cracks and some oxidation. He said they can be repaired by reheating the soldered connection to re-melt the joint. Probably a new relay is a better solution.
His last suggested spare part is a jumper cable with two alligator clips. The explanation for this is a bit lengthy. When the LH2.4 fuel injection computers in these cars fail, they lose the internal ground that activates the fuel pump relay. At the same time the computer also loses its self diagnostic feature. A replacement computer solves the problem, but costs $1500. If you are on the road you can get going again by using the jumper to ground the spade terminal on the relay that accepts the yellow/black wire. This wire comes from terminal 21 on the computer and heads to the pump relay. It is the only yellow/black wire in the connector and jumper it to ground and you are off. This fix is only to get you home because the fuel pump will keep running until the car is shut down and that is a potential safety hazard.
It would be nice to know what tiny component in the computer fails to cause this expensive problem. I bet it is insignificant and easily repaired as is the case with most electronic boxes. Hopefully someone will solve the problem and save us a good chunk of the $1500.