camshaft position sensor 850/1994

[tinroof]

After replacing the cps, I had same problem with '93 850. During one of the failures to fire, I checked fuel pressure and there was none. Replaced fuel pump, and its fixed.

[tinroof]

After replacing the cps, I continued to have same problem with '93 850. During one of the failures to fire, I checked fuel pressure and there was none. Replaced fuel pump, and its fixed.

[Guest]

Andrew said:

"$240 for the CPS? Was that Canadian?"

Nah, Pennsylvanian. ; )

And my failing memory recalls it was about $153 or so from the dealer...

Took me about an hour but I take that cautious vs. rip-it-out approach, at least the first time I do auto work. It definately fixed the stalling under all conditions after the engine warmed up problem back then.

[CasperVolvoInsane]

I have a 93 850 glt and am having the same stalling problems but mine only happen in wet weather, same codes are pulled saying no cam shaft sensor signal but also no rpm sensor signal. I noticed the rpm one since I am getting no reading on my dash. So I bought first a replacement RPM sensor from FCPgroton.com for $45.00 (by far the best and cheapest place anywhere I have looked for volvo parts) and switched the part out and there

[greg94/854]

My 94 nonturbo 850 will sporadically not restart after brief (2 min) shutdown.

If it sits for 5 min it restarts and runs perfectly - go figure

today, after sitting for 10 hrs at work, it wouldn't start.

I pulled air filter, dist cap(perfect) and jiggled cam sensor connector while I was under there.

I put everything back & car started & ran perfectly.

Only code was hi/lo bat voltage (I replaced 8 yr old bat last month)

185k mi

[shamrock22]

I have had no problems knock on wood since I changed my CPS. Additionally no problems with Tach when I had CPS issues.

[njauditor]

I just replaced my CMP this week. I bought mine from FP Grotten in CT for $135.00 plus $6.50 postage (compared to the Volvo dealer's price of $210 plus tax). The FP Grotten part was genuine Volvo. The actual replacement of the CMP was not a problem. Only two bolts holding it to the side of the engine. I had a terrible time though, getting the electric plug out of the holder to put the new one in. For the benefit of those who don't do this every day like me (I'm a CPA), the trick is to use a small screwdriver to force the tab behind the plug down, then work the entire assembly out towards the drivers side with a needle nose. If anyone has any questions, i can explain further. I spent the better part of two hours figuring this out.
Bottom line is the car would not start, gave me codes of 314. After I replaced the CMP it started right up and runs like new.

[greasefingerss]

These both the Cam & crankshaft sensors are very hard to troubleshoot. Both sensors are Hall-effect type sensors. On most all of the vehicles that I have worked on, if either one of these go bad; then it will result in an engine no-start issue. The computer will prevent spark to the engine.

Because it is a Hall-effect sensor, this means that if you hook a voltmeter up to the output line and ground, then you will see the meter constantly oscillate form 0 to 5 or 8 volts. The output is a voltage sine-wave over time. So an oscillating voltage on the meter would mean that the sensor is probably doing its job. If you see low constant output or zero volts, then the sensor is frigged. Back-probing the sensor and testing with the engine running is the only way to check without a good ODDII scanner. An oscilloscope would be really cool and geeky!

One can check to see if the computer is supplying a good ground and power to the sensor, but this is usually fine and it is the sensor that usually goes bust.

[stevegs]

Looks like I'm (nearly) in the right area of your site for posting my problem.

I have owned a '94 850SE estate with a 2.0 litre 20V engine for about 18 months now. Apart from 3 occasions when it refused to start, it's been fine. These have all been when the engine has been luke-warm - it always starts fine when stone cold or hot.

Occasion 1) Started fine from cold and drove 2 miles. Went into a shop for about 10 minutes and it restarted with difficulty. Got onto a busy ring road and it stalled (yes - was I popular!). Restarted with difficulty, but misfired for about 1/2 a mile, after which it cleared and was fine. Two further 10 minute stops on the way home after 10 and a further 20 miles - restarted with no problem.

About a week later, I checked the codes and found, among a host of others, the camshaft position sensor codes (intermittent and absent signal) were flagged up. Since I didn't know how long these faults had been logged (I'd only had the car a month), I reset all and checked connections. Rechecked the codes about a week later - nothing flagged.

Occasion 2) About 3 months later, had to deliver something heavy about 1/2 mile from home. Restarted OK and then went to tyre depot for replacement tyre - about another 1/2 mile. Fitting took about 20 minutes, after which it spun the engine but flatly refused to fire. Tried a few more times and decided to wait - didn't want to confuse the lambda sensor with too much unburnt fuel. Tried again after another 5 minutes - just the same. Pushed car into their yard, walked home, had a cup of coffee, and then back - 40 minutes in all, and it started fine. I checked the codes, and only the camshaft codes were flagged. This time, I thoroughly cleaned the connector to the wiring harness and found it wasn't locking home properly - the shroud on the sensor plug was too deep, so I filed about 1/2mm off it. The locking device then snapped home properly. I resistance checked the sensor and got readings from each pin to the other 2 - I didn't know what to expect, but there were no shorts or open circuits, even when I flexed the lead with the meter connected.

Then no problems at all for 9 months , including a holiday in Ireland (1000 miles) and a trip to the Newcastle (650 miles), so I thought I'd nailed it.

Occasion 3) Drove 20 miles to a meeting, so it was properly warmed up. Came back after 3.5 hours and again it spun but wouldn't fire. The exhaust manifold was still slightly warm. This time, since the whole lump was at the same temperature, it took longer to cool down and still wouldn't start 40 minutes later. I had called out a breakdown company, but they took about 90 minutes to arrive - ie. 5 hours after I had arrived for the meeting. Needless to say, it started fine - embarrassing! While waiting for the breaker, I checked the fault codes - again only the camshaft sensor codes were flagged.

The breaker man said the problem could be an engine temperature sensor and recommended a Volvo agent to use their diagnostic kit. This would be a pain since the nearest is 15 miles from home.

Someone else has told me all 850s have this problem - a possible bug in the engine management unit - anyone else heard anything like this?

What isn't clear is why, if it's a temperature sensor gone for a walk, the camshaft position sensor is being 'blamed', or if it IS the camshaft sensor, why does it only do it when the engine is luke-warm but not when cold or hot?

Any comments would be appreciated.

[Ozark Lee]

It could just be that the cam sensor is going bad. They get flaky before they quit entirely. They are expensive so, since you fault codes suggest an intermittent fault, check the routing of both the cam position sensor and the crankshaft position sensor in relation to the coil wire.

There are slots on the air intake box that should route the coil wire away from the sensor wires but quite often, usually after an air filter change, the coil wire winds up drooping down near the sensor wires and causes the ECU to get confused. There is a service bulletin that says to tye-wrap the sensor wires to make sure that they don't get close to the coil wire.

...Lee