I have been searching for weeks for help with my problem and keep finding a lot of conflicting information out there. I have a 93 850 wagon 5 speed that suddenly died on the highway. Had it towed home and there she sits. It's been about two months and every once in a while I get inspired to take another stab at it. The previous owner had issues with it not starting intermittently and his garage replaced almost everything in the ignition system. New plugs, wires, cap, rotor, coil and controller, cam sensor and tps. The only thing left is the crank sensor. I don't want to purchase the part though if it isn't going to solve the problem.

Will a bad crank (rpm,speed) sensor (not cam sensor) cause a no spark situation? Also will a faulty fuel injector relay cause a no spark situation? because I also noted that the injectors are not firing. I have pressure at the fuel rail but my plugs are coming out dry after considerable cranking. Or is this by design, that if if there is a fault in the ignition system it automatically stops fuel delivery to the engine to prevent flooding or something? The codes I am getting are all for parts that have been replaced. They were probably never cleared by the garage that was working on it before I got it.

 

So clear the codes. It is possible that a new part can fail in days or weeks.

Conflicting? Trouble shooting can go down different paths. Also, part of trouble shooting includes replacing different parts.

 

did he ever talk about the posibility of having a bad fuel pump relay?same happened to me.

 

Bad fuel pump relay won't stop spark.

 

This is what I mean. One poster saying that he had a similar experience with a bad fuel pump or injector relay and another who says that bad relays will not cause a no spark condition. I wanted to know if these parts would cause no spark 1. Crank sensor 2. Fuel pump or injector relays. I have cleared the codes, my point was that codes are not going to help diagnose this problem since the codes were never cleared by the shop working on it before me and now it won't start.

 

I thought it strange that the ignition and fuel system would both fail at the same time. This is why I was wondering if Volvo in their infinite saftey wisdom may have designed it such that if there is a fault in the ignition system that the fuel system is cut off. Like I said in the original post I have no spark and the injectors are not firing. I have fuel pressure at the rail just that injectors are not opening during the cranking cycle. This is an assumption and assumptions can be dangerous and expensive that is why I have brought the question to you all.

 

The relay above the radiator controls the injectors...and I believe has an affect on the ignition. See if there is power there.

 

They didn't design it that way for safety it's just the way it has to be as that crankshaft signal is what the ECM times everything off of. It's how it knows where the pistons are in their travel and when to fire the plugs and injectors in the proper timing related to each cylinders cycle.

I haven't had the crankshaft sensor fail on my Volvo so I don't know for sure specifically on a Vovlo BUT from what I've read when you lose the crankshaft position signal you lose both ignition and injector pulse.
That is the way it works on the cars I've worked on.

 

Thanks, that makes sense to me.

 

If you are a guy who likes to have a diagnosis before he buys parts, then you should definitely try this:

http://www.volvoclub.org.uk/tech/ser...sicTesting.pdf

Ignition checks start on p. 5 I think. If you can find a 93 manual, so much the better.

 

I was trying to find the resistance on that crankshaft sensor and the best I can do is a guess 150 to 200 ohms. That was the value for a s70 with a 2.3

If you are lucky and you test it with a meter it might show it's shorted, no ohms or open and has infinite resistance. Either of those two and you know for sure it's bad.

Maybe someone else knows what the spec is for it

 

Found the spec for my 85 turbo 2.3 crank sensor or as Volvo calls it "Engine Speed Sensor".
I'm guessing they are all going to be about the same.

ENGINE SPEED (RPM) SENSOR RESISTANCE TABLE
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Application Ohms
850 .............................................. 260-340