mulcy Posted September 20, 2010 Report Share Posted September 20, 2010 So... this starting problem is nasty. It's 100% a spark problem. For a long time the car has been hard to start, and now it won't catch at all. (Once it's running everything works fine) Fuel pressure is good and injectors are firing. I'm using the ignition diagnosis protocol that can be found here to try and track down the fault: http://www.volvoclub.org.uk/tech/service/850/BasicTesting.pdf So far I've determined that the cam sensor is good, the rpm sensor is good and the coil is good, but that the "control signal" in step 8 is incorrect (I'm seeing ~.3 volts at the power stage and it should be .7 - 1.3 volts). I'm also seeing ~ 10 volts at the blue wire on the coil when I should be seeing .7 - 1.3 (while operating starter, step 3). I need a breakout box to figure out where the "control signal" is getting messed up. It could either be in the wiring going from the cam or crank sensor to the ECU, in the ECU itself, or in the wiring coming from the ECU and going to the coil. Anyone know where to get a Volvo Breakout Box (981 3190) and Adapter (981 3195)? Any other suggestions? The car's in pretty good shape aside from this problem so I'd really rather not have to part the old girl out...ps. It's a 94 855 NA Look at me, I think I am witty Link to comment Share on other sites More sharing options...
Reximus Posted September 20, 2010 Report Share Posted September 20, 2010 did your check engine light come on? like did you check the computers if there is any error codes? Link to comment Share on other sites More sharing options...
Xero Posted September 20, 2010 Report Share Posted September 20, 2010 You may be able to save some time and money by buying a used computer. I bought both the ecu and tranny computer from a local junkyard for about $70. My 850 had similar problems as yours and the computers fixed my problem. I hope this helps you out. Link to comment Share on other sites More sharing options...
mulcy Posted September 20, 2010 Author Report Share Posted September 20, 2010 no CEL but I am getting 314 and 214 codes (cam and crank sensor) even with known good sensors. Makes me the ecu itself or the wiring from the sensors back to the ECU is the problem. Link to comment Share on other sites More sharing options...
Xero Posted September 20, 2010 Report Share Posted September 20, 2010 Mine kept throwing tps codes. Tps was fine, computer was shot. I bet yours is, too. You can always check for chewed or burnt wiring. Good luck! Link to comment Share on other sites More sharing options...
Guest Matt Posted March 10, 2011 Report Share Posted March 10, 2011 Anything new on this topic. I'm having the same exact problem on my 850 Turbo wagon. All the same symptoms as the original post. And also I'd like to know where to find a breakout box. If anyone can shed some light on the subject, it'd be greatly appreciated. Link to comment Share on other sites More sharing options...
Oldariel Posted March 10, 2011 Report Share Posted March 10, 2011 You may be able to save some time and money by buying a used computer. I bought both the ecu and tranny computer from a local junkyard for about $70. My 850 had similar problems as yours and the computers fixed my problem. I hope this helps you out. I would second that. A while ago I had some codes on my 93' 850 ECU too, which were obivously not true (the code was absent signal from a sensor, but the sensor was new and functioning properly). It turned out the ECU was defect. I think it's the simplest approach to replace the ECU, just for a test with a boorowed good unit . If the code and no start condition still persist with the new ECU, you know it's not the ECU and can start looking at the wiring. Link to comment Share on other sites More sharing options...
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