850 T5 intermittent starting

**Blackdog** · Tuesday 15th September 2015, 13:42

You may be surprised.

I think what it does is break the misread link between the key and the immobiliser as the key is removed from out of the antennas range and it is then reread as the key is reinserted.

If it does work it would point towards the antenna breaking down and needing replacing.

**mike 850** · Tuesday 15th September 2015, 14:17

is there a way on the 850 to temporarily disable the immobiliser?

**kmb** · Tuesday 15th September 2015, 15:04

I read somewhere on here that fuse removal disables the alarm (and central locking), but not sure if that has anything to do with immobiliser.

Think it was fuse 6 from some cloudy memory whilst reading old threads about remote fobs

**Sparkysparks** · Tuesday 15th September 2015, 17:01

Fuse 6 then 16 ive read. I shall try that aswell. Fingers crossed for the easiest fix in the world.

**Sparkysparks** · Tuesday 15th September 2015, 19:28

Ok. Progress. After going through the basic f test and finding that everything is wrong. I lost patience and beat up the ecu a little bit. Cleaned the contacts and tried to make sure I had a good connection.
Tried the key thing to no avail. Many many times.
Then I had a look under the fuse box and thought. I'll just make sure everything's down. Pressed the first one and the fuel pump fired up and the icv buzzed. Cranked ot and after about 10 seconds it fired up. Hooray!!
Let it warm up. Started it a few more times cranking time varying between 1 and 10 seconds. So something is still wrong. But its working now. Thank fudge for that.

**merc85** · Tuesday 15th September 2015, 20:05

There is a way by bridging to pins on the fuse board under the dash using a jumper wire but cant rember what terminals it was a long time ago i had all this.

Btw may be worth you temporarily running a new trigger wire directly from the trigger pin on the ecu to the ignition module on the coil. this will improve the strength of the signal and tell it when to through a spark. I have a lengthy thread on all of this on my car which was called Blacky.

In the end it was down to a incorrect flywheel which was fitted.

**Sparkysparks** · Tuesday 15th September 2015, 20:45

Ok, sounds good. An incorrect flywheel is a distinct possibility as its had an engine swap.

**merc85** · Wednesday 16th September 2015, 17:58

Originally Posted by Sparkysparks

Ok, sounds good. An incorrect flywheel is a distinct possibility as its had an engine swap.

I made that mistake,
OBD1 850's have a different flywheel to OBD2

I believe OBD 1s have Holes recesed/drilled into the flywheel
Obd2 have Raised squared lugs on the flywheel.

To Try this out reverse the polarity on the crank sensor Ie turn it around and this should make it fire up 1st time.

There is a Volvo technical buliton on this. You may have to file the location lugs on the sensor plug for it to be connected to the socket.

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**Sparkysparks** · Wednesday 16th September 2015, 21:35

Is this a permanent problem of starting with the wrong flywheel? As mine starts now. Is this an indicator that its got the correct one if it starts stall?

**merc85** · Wednesday 16th September 2015, 23:20

With the wrong flywheel fitted you will find the colder the weather gets the harder it will become to start, this is due to the signal wire voltage, as this gets less with the colder weather. (not sure why) but it did with mine.

I in the end did fit the correct flywheel as i wanted it done properly once id found out it was the issue.

**Sparkysparks** · Thursday 17th September 2015, 07:49

Interesting. Is there any chance I can see through the crank sensor hole to see which one I have?

**merc85** · Thursday 17th September 2015, 07:53

Yes buddy you may be able to using a led torch or similar

**Sparkysparks** · Friday 18th September 2015, 08:01

Ill have to give this a check when i get a minute. Its starting but still playing up cranking.

**Sparkysparks** · Tuesday 22nd September 2015, 19:09

This guy knows his stuff! Reversed the sensor temporarily and it fired up after about 1 second cranking. Done this about 10 times. Swapping it about with consistent results. It starts straight away swapped round. So. It runs less than great though, does this mean that the flywheel is wrong. And is it advisable to drive it with it swapped. Is the overall problem that the sensor is not close enough to the flywheel. Can I reduce the gap and be happy?
Thanks
Mark

**kmb** · Tuesday 22nd September 2015, 19:15

Very pleased to hear you're getting somewhere on solving this problem, looks like some good help above

**Sparkysparks** · Tuesday 22nd September 2015, 21:42

Yes, this is very good news.
Im considering putting a switch in for cold morning starts, as that really does seem to be the worst.

**merc85** · Tuesday 22nd September 2015, 22:34

Sounds like you have a incorrect flywheel, Blacky ran fine with it switched round. is the sensor a new one? The correct course of action would be to fit the correct flywheel. Wish i could remeber where that tech bulltin was :/

**Sparkysparks** · Wednesday 23rd September 2015, 06:53

The sensor is new. But I think I'm going to run a switch from behind the sensor. So a switch for cold starts. When I had started it with the sensor switched round it didn't like being revved and had a flat spot on the accelerator.

**PNuT** · Monday 28th September 2015, 19:20

Originally Posted by merc85

There is a way by bridging to pins on the fuse board under the dash using a jumper wire but cant rember what terminals it was a long time ago i had all this.

That will bypass the alarm module, not the immobiliser....

I have searched long & hard of ways to bypass the immobiliser & it appears the only way of doing it is getting your ecu modified.....