I have a couple of issues that are puzzling me. First, my 1988 740 will sporadically not turn over. It sounds to me like it's not getting fuel to turn over. The battery/alternator seem fine. And this does not happen all the time. If I let it sit for a while it will start up. But the problem is become more common.

The second issue is that I'm losing several components of my electircal system. That is, the power windows, don't work, the speedometer works/doesn't work randomly and several "idiot" lights flick on/off at will. Any suggestions? Thanks.

 

when you say will not turn over that would imply the starter is not working and I would think looking at the voltage from the ign switch to the starter and the ground return would be in order. If you mean the engine turns over but does not start it could be the hall pickup in the distributor, the ign module on the drivers front fender, or the radio suppression relay on the coolant bottle (supplies 12v to injuectors) or fuel pump relay or one of the two fuel pumps. Now having said that I think your problem is much simplier since it is affecting alot of other components as well. I suggest Diagnosing automobile electrical systems by Tracy Martin. Best book on the subject I have ever read and worth its weight in gold bullion. Start your car turn on the headlights and measure the voltage drop from the positive side of the battery to the positive side of the starter. It should be very low (.2v-.4v) now do the same thing on the negative side again voltage drop should be very low. If it is high you have a bad battery cable or a bad connection. If you read his book and get a volvo wireing diagram from volvo tech publications you will be able to fix anything on your car. Hope this helps

 

You need to know two things: 1. Is it the engine getting gas; and, 2, is it getting spark? The spark is easiest to check. Disconnect the h/t lead from the coil to the distributor at the distributor end. Hold the metal tip of the lead near the engine block. Use gloves since the spark can travel in search of a ground (you) Have someonee turn the engine over while you watch for a fat, juicy spark. If you get a spark, you may conclude that the electrical system is working - at least well enough to start the car. No spark? Your problem is electriccal. Spark? Your problem is probably in the fuel system. This is not rocket science, just basic troubleshooting. If you have a spark and smell gas, the engine might not be getting the right mixture of air and fuel. Then the Lambda system may bee at fault, or one of the sensors that are part of it - oxygen sensor, air mass sensor or engine teemperature sensor. Or even the computer module itself. In self defense, I have accumulated some spare componenrts for a quick and dirty swap check. I had a nasty intermittent problem with the engine temperature sensor - it would work fine on a cold start, but would refuse to start the engine on a hot start - intermittently. The fact that your engine won’t start at all is good from one standpoint - the problem is consistent and can be diagnosed. Intermittents are devilishly elusive.