Intermittent issue has gotten worse.
850 stalls (usually when coming to a stop) and now won't start. Before, I would just wait a couple minutes and it would turn over again.
Minutes have turned to hours... replaced the fuel pump... wrong... replaced the fuel pump relay... not it.
Have been reading all codes and posts and have checked for leaks to/from air box..
last code readings showed both 3-2-4 and 3-1-4 in the electrical readouts (A-6) which seems to indicate no signal or intermittent signal to camshaft position sensor.
Not a cheap item to replace... before I go and replace this is there anyway of checking whether the sensor
has truly failed or not? Could it be wiring or dirt?

Before i replace it I am going to do a fuel pressure check just to eliminate fuel delivery as the issue.
My Fuel (A-2) codes read 1-1-1.

I appreciate your comments.

Check the resistance of the cam position sensor with a multimeter, readings should be around 200, I think.

A 'bad' reading by the ECU will prevent the plugs from firing. BTW, that is an OEM part, knockoffs have been known to fail early and often.

Klaus
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Two great Volvos, a 1967 220 and a 1998 V70R

Do I have to remove the sensor in order to measure the resistance?
As this is an intermittent issue, do I have to wait for the car to "fail" before taking the readings?
I just had it out to my local mechanic for a fuel pressure and air Mass test... do you think I could get it to fail?
Not on your life... of course it ran perfectly for over an hour, driving around and idling etc.

Will check the resistance... do this before or after failure or both?
.
Incidently I cleared the codes for electrical yesterday (A-6) to 1-1-1 and while over at the mechanics, took another look and again got the code for no connection to cam position sensor... even though the car was idling fine... is that the way it should be? Or should the code have not shown?

Thanks for your comments and wisdom.

OK everyone... have replaced the CPS and so far everything seems to be working fine... no stalling or non starts. Picked up a used one but it did cost (a lot) more than $10.00. Eliminated air mass and fuel pressure at the rail and checked for hose leaks etc. as suggested before replacing CPS
Codes showing no CPS connection did not reappear after replacement and codes were cleared.
Hooray for 1-1-1

Thank you very much to all who contributed in solving this dilemma.... should have come here earlier.
Your generosity is greatly appreciated.

"93 850 (407+)

Just unplug the CPS, and measure the resistance on the plug that goes to the CPS. Do it with the ignition off, please. Do it now, and again when the car fails to start.

When it fails to start is alos a good time to check a spark plug to make sure it is firing. Remove the plug, put the cap back on, ground the threads of the plug against the block or some other unpainted/grounding steel, and crank the starter. You should see a spark arcing across the electrode. No spark usually means the CPS is dead or sending the wrong signal.

Make doubly sure that the CPS wires go under the distributer and the wires do not touch any of the sprk plug wires.

Klaus
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Two great Volvos, a 1967 220 and a 1998 V70R

Thanks KlausC for the extra input... should I see a difference in the resistance in the CPS plug before and after failure. What kind of reading would indicate a bad CPS? Or should I just rely on the spark plug test?

Really appreciate your help...

I will go through this tomorrow and post a result... thanks again.

http://www.brickboard.com/AWD/volvo/1311340/850/camshaft_sensor_repair_information.html
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Two great Volvos, a 1967 220 and a 1998 V70R

Klaus said the reading should be around 200 ohms, he thinks.

Do the tests and post the results. The spark plug test is another way of verifying the CPS is faulty. Do the resistance tests and the spark plug test. Having all the info allows you to have greater confidence in your conclusions.

you can pick up a couple of OEM cam sensors from wrecked cars( which were running last heard of)a your local u pick for around $10.

Your codes sound pretty conclusive, but check the condition of the wiring to the CPS, make sure they avoid spark plug wires especially, and that the connections are tight and clean. If you have a pick-n-pull nearby, you might try a "recycled" sensor, but I wouldn't want to rely on a used one for very long. Not sure how interchangeable the early sensors are with later ones, you'll want to check on that if you go the pick-n-pull route.

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'96 850 and '83 244 DL both at about 200K; gone but not forgotten '81 245 and '64 Amazon