I'm stymied by a starting problem. My 1996 NA 850 cranks but won't start. There's spark at the plugs, fuel at the rail. I happened to have a spare cam position sensor and crankshaft position sensor around, so I changed those out. Still nothing. Recent cold here in Minnesota, which I raise as a point of consideration. Next steps? I'm running out of ideas.

 

I just had this problem this week. The temperature sensor was bad, and it finally got cold enough to fail to start. I started it on ether, and after it got a little fire in there it would run. I have an OBDII scan tool, so I am able to plug up and see what temperature the computer thinks it is. Anyway, I had to replace the sender. That is, they say, typically the problem, and that did fix me right up.

 

Temperature sensor is a good start. One way to be SURE and narrow down the problem is use a 2 second burst of starting fluid in the air intake and try to start it. If it starts and runs for a couple seconds, you have a fuel issue. If it does not start, you have a spark issue or a timing issue. I know you said you have spark, but is it hot enough to sustain combustion? Same as for the fuel, you may have fuel at the rail, but is it under enough pressure? Starting fuid will narrow down (or eliminate) if there is a fuel or spark issue.

 

You could have a bad fuel injector relay. That stops the injectors from opening when they are suppose to. You can try spraying starter fluid in the vacuum tree to see if that helps.

 

My experience with the fuel injection relay is that you get no spark when the relay drops out. It doesn't power the coil, so I suppose this is because it also powers something in the ECM.

 

Thanks, all. An update: I grabbed a new temperature sensor and threw that at the problem. Also tried some starting fluid down the air intake. Still no go. RSPI — I had already watched your great starting diagnostics video, but had not seen the lawn mower syndrome piece. That opens another path of exploration (although the idea of letting the car crank for a minute seems a little alarming). Part of my fear on this is that there are yards worth of 20 year old wiring, and one little piece of it might be the source of my problems. Tomorrow's another day, so if anybody else has some insight, I'm eager to hear about it.

 

Try RSPI's suggestion just to see if it helps, but if you sprayed starting fluid down the intake and it did not start or run for a few seconds, then you most likely have a spark problem, or a remote chance of a timing issue. The fuel injection relay that firebirdparts mentioned might be part of the issue if it causes no spark. I know you said you had spark at the beginning, but if you are not getting it to fire using starting fluid, it sure ounds like a spark issue to me. Do you have a way to check the compression?

 

Thanks for the additional suggestions. Unfortunately, the 850 has to get in line behind our 2000 Saturn, which decided this would be a good time to snap an axle.

I think I have a fuel injector relay in the garage, so will try swapping that out. And I can borrow a compression gauge over the weekend to see what's going on there. My gratitude for all the help.

 

No problem, that is what we are here for...to help when we can. Whenever I have a starting problem, I always remember what is needed for an engine to run......Fuel, spark, compression, air, and all at the proper time....Good luck and keep us posted.

 

Sorry to have fallen off the face of the earth on this, but there is a conclusion to the story, sort of. In early January I replaced the engine coolant sensor and the thermostat, as suggested above. Still nothing. This was on top of throwing in a junkyard cam position sensor and crank sensor. So I pushed the car off the street and into the driveway, then went to Florida for most of the month of January.

Before I left I removed the battery for reasons related to my neighborhood (people will steal some surprising things around here). When I returned, I charged the battery, reinstalled it, and thought, well, what the hell, I'll turn the key and see where I'm at. The car started right up and has run fine since.

The natural question here, I suppose, is whether the battery was low all along. But I had recharged it while making the various changes described above. I'm happy to have the car working again, but I'm not sure I learned anything in the process. If it were my laptop, I'd wonder if turning the thing off and on again had rebooted it and put me back in business. Is this even a remotely plausible explanation for what might have happened after installing some different sensors, removing the battery and replacing it?

 

In the future, if you want to learn, you'll need an OBDII scan tool and also a willingness to test things that can be tested directly. You could still learn by removing all the parts you put on, I guess.

 

Do have the scan tool, but there weren't any codes. Admittedly I was lazy about testing the sensors.

 

Not talking about codes. I was talking about when you say "I wonder what temperature my computer thinks it is?" With the scan tool you can look at that. If it won't start cold, and you look with the scan tool and the ECU thinks the coolant temperature is 220F, then you found your problem.

The data is far more revealing than codes.

 

One thing to watch out for when changing out a battery.
The positive battery terminal on these Volvos is different than any others I've seen. I had a problem with mine killing due to the smaller wires on the positive terminal being loose. All other terminals you tighten one side and it's tight. The positive terminal doesn't have a bolt going all the way through and you can tighten the one to the terminal and if you don't know about it leave the other one loose.