We have an '94 850 Turbo with 103K miles. In the last 3 weeks it has developed a problem starting. It often happens after the car has sat for one hour. It doesn't happen after it has sat for days without running. My mechanic, is having a tough time finding the problem, because after I have it towed to his shop, it starts. And, of course, it started everytime he tried it during a week at his shop. Then I drove it home (about 2 miles), and an hour later it wouldn't start. He has tried replacing the the O2 sensor, since it registered some errors, but that hasn't corrected the problem. He gave me a spare relay to try, but that didn't correct it.

This is getting expensive and frustrating. Any ideas?

Now this will sound strange, I had '94 850 Turbo, 90K miles, and it would do similar things that your are saying, by accident, I realized something that changed it. You know where the headlight switch is, and how you can have it set for 'day time running lamps' vs. headlights on; when I left it in the headlights on position, it would never start, swithed it off, started like a champ. Never had any indicator lights etc, similar issue, took to dealer, they couldn't figure it out. Now this could be a fluke loose connection, and that switch may have just triggered something, but it worked.

I just had the fuel pump replaced. it started, ran fine, then wouldn't start. then it would start, so I drove around to make sure and it was fine. started next day, made a couple of stops and after last stop of course it wouldn't start. error codes indicated EVAP system, but I had a shop look at it and they said it was the fuel pump. the dealer wanted $339 (gasp), I decided to wait an extra day and bought it from alloemvolvoparts.com for $171 + $17 for overnight shipping. the cost of the part, shipping, tow to shop and installation was still cheaper than the part alone from the dealer.
hope this helps and good luck

Mouseface2,

Thanks for the input. I shared it with the mechanic. My problem has been going on for 4 weeks now. He says there is no way it takes 4 weeks for a fuel pump to fail. How long was your sporadic starting problem? At the end, did it fail completely? Another point... about a week ago, my car wouldn't start, and I had the mechanic come over... at one point in the system, he found that it wasn't getting fuel or spark. He feels that this is further demonstration that it is not the fuel pump. If any of this helps you to help me further, I would appreciate it.

Over what period of time did you have your problem before replacing your pump?
Did you feel that after its last stop, it wasn't going to start again?

Are you saying that the first fuel pump you installed was defective?

Has your mechanic checked the fuel pump? I had the same problem of intermittent difficulty starting that eventually turned out to be a fuel pump. I just found a cracked vacuum line (see thread for high pitched sound); those can probably cause O2 sensor codes, so have your mechanic check for those or check them yourself. The instructions are under www.volvospeed.com look under repairs.

Good luck, these cars are great but things start needing to be replaced after 100k.

Does it crank but not start or not crank?

It cranks like a champ! But that is all.