850 t5 94- ? immobiliser problem, intermittent non starter

danw · Post by **danw** » 28 Feb 2009, 22:34

Hi, over the past fortnight or so I have been experiencing a problem when trying to start the 850, the engine is turning over fine however nil spark.. I am thinking this is the immobiliser as a couple of times I have unlocked the doors with the key and then used the remote with success however this is not an exact science. I have also changed the remote battery, once again intermittent problem. I believe the immobiliser is after market, not quite sure however, can anyone guide me in the right direction before heading to the mechanic? Where is the immobilser situated and is it possible to simply bypass it if it is faulty.. As a footnote I did notice prior to the non starting issues that occasionally the doors wouldnt always lock and subsequently I would have to recheck.. Thanks

jonofmac · Post by **jonofmac** » 28 Feb 2009, 23:23

Hey, I think I know what you're talking about, My 1994 Volvo 850 also has the intermittent cranking without any firing. Upon research, I found that a common problem of this is due to the Camshaft Position Sensor. Due to the age, it sometimes doesn't read correctly when you crank the engine and I guess the ECU doesn't fire.

For me, once it does this, if I stop holding the key in Pos 3 and then try to start again it'll normally fire right up. If you're having problems like this, I'm pretty sure it's an aging Camshaft position sensor.

They're not the cheapest, it can be had for $179 new on ipd.
http://www.ipdusa.com/Volvo-850/Engine/ ... -155-3823/

That's my opinion about your problem. I can't promise it'll fix it, but I believe that is the cause because I have the same problem, and I have no immobilizer, and even so, your immobilizer shouldn't prevent firing, it should prevent the starter motor from even starting at all, no?

Hope this helps!
Jonathan

Post by **Ozark Lee** » 01 Mar 2009, 05:02

Danw

I believe the immobiliser is after market, not quite sure however, can anyone guide me in the right direction before heading to the mechanic?

All bets are off on that one. My son had an aftermarket remote starter, alarm, remote door lock system in his car but we didn't know about it until the starter went bad and blew the thing up. I simply undid what the hacks at the installation shop did and it all worked again. I then installed an eBay remote receiver so that he had a remote for his locks. I got the receiver, the remote key fob, and a replacement ignition switch with the key for $35.00. Installation is a snap - it just plugs in and then you program the remote. My son had it done in under 30 minutes.

The factory immobilizer disables the starter so that the car won't crank. There are dozens of versions of the aftermarket remotes and they all do different things.

Johnofmac is correct when he notes that a flaky CPS can cause the problem with crank / no start but that is with an un-tampered with system. A bad CPS should post a code as it dies but I have seen cases where it dies suddenly and it never sets the code since the car needs to be running before it can figure it out that it is bad - the car won't start unless it works. It is a chicken and egg thing.

...Lee

danw · Post by **danw** » 02 Mar 2009, 13:38

Yeah thanks guys unfortunately both your posts seem to be valid..thus is my dilemma!

As it stands the engine is cranking with nil firing therefore I am under the assumption that the immobiliser is not to blame as if I am correct shouldnt the immobiliser disable the starter?
However maybe with the aftermarket locking alarm immobiliser system this may affecting the system? Who knows!!

What I would like to know if anyone could help is, where is the immobilser brains situated? and what should I be looking for? is itpossible for me to bypass this so I could rule out this as the problem and thus save me from having to by a CPS...

Cheers guys thanks for the input much appreciated..

Post by **Ozark Lee** » 02 Mar 2009, 14:15

What I would like to know if anyone could help is, where is the immobilser brains situated? and what should I be looking for?

The factory immobilizer is under the driver's side dash in the lower portion of the central electrical unit. It is relay 210/211.

The lower portion of the central electrical unit is directly below the fuse box, on the inside of the car, high on the firewall.

Most of the aftermarket systems will be in the same general area. They are typically just tye-wrapped to the wiring harness in a real sloppy manner.

...Lee

javajay72 · Post by **javajay72** » 02 Mar 2009, 15:01

Does your 850 have a diagnostic unit?If so what codes did you get?I'm waiting to see if someone can answer my dilema.My problem started out like this.It ended up being a broken timing belt.If yours turns out being the camshaft censor i have two that would probably do the trick that i don't have a use for now.I thought my ECU was damaged but later realized i wasn't accounting pauses for zeros.I self educated myself on a lot of stuff due to overlooking the diagnostic unit.Hope this helps

Jay

danw · Post by **danw** » 02 Mar 2009, 20:14

I have checked the diagnostics and have come up with a faulty or missing CPS.. I have cleaned the connector but still have an intermittent problem, so I guess I should start with replacing the unit and see what happens. Jay I'll send you a PM , thanks for your help.

Post by **stone36** » 02 Mar 2009, 20:30

If it turns out to be the Cam position sensor, check you local parts yards. I know some don't like buying eletrical used, but I have found they either work or they dont. When mine went out, I picked two up for $10 each, the first one I put in worked and that was over 3 years ago. better than the $180 or so from the dealer.