1993 850 Cranks, No Start
 

I'm hoping that someone has experience with this and maybe has figured out a fix for my strange issue. It's an intermittent problem, which is always the worst, where it'll crank but won't catch and actually start. Pulling codes gives me 1-3-1 (from terminal A slot 6), which is no signal from VSS. I have no clue what VSS has to do with the ignition sequence, but apparently that's what the car says is the problem.

I have checked, and when it won't start like this there is no spark. Cam sensor was replaced recently. As far as I can see, VSS contacts are good, but I can't see it very well. I'd rather not just throw parts at this and hope for the best, but I can replace the VSS if people think that may be the actual problem. I think it's more likely that there is some wiring issue, but am really hoping not since those are terrible to track down.

Any thoughts or suggestions would be appreciated!

check the fuel injector relay - its up under the cowling over the top of the radiator (I think its gray).

I can hear the fuel pump working (humming) when I put the key in pos II without starting, so I think the relay is working.

The main fuel injection relay powers a couple of pins on the ECM such that the OBD sockets on the early 850's don't work. In fact the LED just glows dimly. So that is the tipoff there. Looks like you are okay. Just to put my mind at ease, you may want to pull codes from slot 2 and make sure it talks to you.

For the OBD 1 cars, you can put them in cam sensor test mode and crank sensor test mode. I guess you have separate fuel and ignition ECM's, right? I looked at the manual and actually you will get a confirmation of signal on VSS, cam, crank, and ECU.

I am reading the manual now and there does seem to be the possibility that this could cause a no start. The manual reads like the crank sensor is the VSS. That is, the VSS will send a signal "when the flywheel rotates" and the speedometer is a separate sensor. This makes no sense but I am convinced now that is what they meant. In any case there is some test procedures for the crank sensor, at least. You can ohm it out.

I like this, but when you get to the breakout box of course you are going to be stuck
https://www.volvoclub.org.uk/tech/se...sicTesting.pdf

Thanks for the response! I checked port 2 and got a 1-1-1, so I should be okay there. Yes, I do have separate ignition and fuel ECMs. I put it in the diagnostic mode 2 and got responses from both the cam and VSS are sending a signal. I don't see where there is a diagnostic mode that checks the crank sensor though.

Yeah, I've been very confused about the description in the manual about the role VSS plays in the system, and the different names, it's very confusing. I'm still not sure what the VSS has to do with ignition at all or why it says the speedometer is a separate sensor.

I think you might be right, the crank sensor may be the issue. I checked the sensor port and the contacts look okay, but are covered in a blue goop. Not sure if this is a contact gel or something, but I haven't seen that on any other sensor plugs. Sometimes, when the car won't start, I have wiggled around that connection and the car might then start (but not always). I haven't had a chance yet to pull the sensor out and look at it, but it's also hard to want to mess with things when the car is actually working for the moment. I'll probably pull the sensor the next time that the car dies, or when I have time.

I was having an issue with a no start on my 96 NA. Turned out to be the ignition coil.