I’ve owned a 1991 Volvo 740 since 1995. Here are some of my lessons learned in the hopes it might help someone troubleshoot or fix their Volvo.
Hard or no start: If you have to use starting fluid to get your car started, check for vacuum leaks and also the fuel pump relay. My vacuum leak was a hole in the bottom of the air tube that runs from the mass air flow meter to the throttle body. It rubs on the bottom and wears a hole. It can be difficult to find unless you take it off and bend it. I’ve since used duct tape to wrap this tube to prevent a similar occurrence. I’d also suggest carrying a spare fuel pump relay (located behind the ash tray). It is simple to swap, and I’ve had one of these fail.
Long cranking time: I had a longer and longer cranking time turn out to the a poor connection at the crankcase position sensor. This sensor connects near the firewall between the engine and the drivers side. In fact, most of my ‘problems’ have been poor connections. I’ve had very few actual component failures. I’d suggest going thru every electrical connection you can find (including the big connector going to the ECU in the passenger’s side front) and using sandpaper or a small file to get to bare metal and then use dielectric grease to prevent future poor connections. I even use dielectric grease on the oxygen sensor signal connection with no issue. Another long cranking issue was a failed fuel pressure regulator. I could clearly smell gas at the vacuum line. A new FPR fixed the issue.
AC compressor not turning on. This was a lucky find. I had 12 volts at the compressor, but it would not engage. This turned out to be a cold solder at a relay found in the AC control unit. I had this unit out and touched the relay when I heard the compressor kick on.
Low idle at cold start. This turned out to be a poorly set throttle position sensor. I heard a click when the throttle was moved, but you need to hear a click when it closes as well. It is easiest to set the throttle body positions removed from the car. You can find the procedure on brickboard.
Check engine light – running lean or rich. This turned out to be a rusted connection at the O2 sensor (before I went thru with dielectric grease everywhere).
Engine ‘skips a beat’ at speed – this was a poor connection at the mass air flow meter. You need to clean both the MAF connection and the connection to the ECU.
Speedometer not working – this was caused by leaking capacitors. I replaced them, and now my speedometer works correctly up to 45 mph. This is documented pretty well on brickboard.
Other maintenance I’ve had to do over 26 years of owning the car are replacing the radiator, heater core, timing belt, shocks and struts. It sounds like I need a new exhaust soon. Many thanks to those who have posted on how to do this.
Best of luck to you all. I love my Volvo. It can be pesky to work on all of these electrical issues, but once you get some practice, it becomes pretty easy.