1995 850 non turbo ignition control signal issue.

themonkeypeas · Post by **themonkeypeas** » 19 Mar 2012, 10:53

Hi all,

Im hoping that there's someone on here who has more know how than me and can solve an issue I'm having with ignition on my 2.0 1995 850 Estate (a.k.a "The Beige Flash")!

I initially started having intermittant starting issues where the engine would turn ove fine but would not fire and needed trying a few times now and then. This eventually got worse and now the car will not fire at all. First test was to check fuel supply and pressure and all seems ok and then I removed the HT lead to the distributor and found that there is no spark. I sourced and have changed both the ignition coil and camshaft position sensor but to no avail.

As this then seemed something more serious, I managed to get hold of the Volvo System Component Test sheets and have worked throgh what I could but obviously I don't have a break-out box to try the more advanced stuff. The results of my tests are as follows:

Coil wire removed from distributor cap: No spark (although gives one spark when stopping turning engine over)
Ignition coil terminal 15 (red wire) to ground (key position 2): 12 volts (ok)
Ignition coil terminal 1 (blue wire) to ground (starter turning): 6.8 volts (should be 0.7 to 1.3 volts)
Coil power stage connector terminal 1 (resistance to ground): 0 ohms (ok)
Coil power stage connector terminal 3 (key position 2): 12 volts (ok)
Coil power stage connector terminal 4 (starter turning): 0.3 volts (should be 0.7 to 1.3 volts)

Engine speed sensor (just test of sensor resistance): 265 ohms (ok)

Camshaft position sensor terminal 1 (resistance to ground): 0 ohms (ok)
Camshaft position sensor terminal 2 (starter turning): 0 - 5 volts (ok)
Camshaft position sensor terminal 3 (key position 2): 9.6 volts (ok)

I have also tested the MAF sensor which checked out ok and have made a box for accessing the fault codes which turns up 1-1-1 (no faults).

Judging by the above results, it would seem that the issue is with the ignition control signal which is not at the correct voltage. Without a break-out box, I am unsure of where to go from here and buying an ECU is a costly next step. Has anyone experienced this problem and know the solution? Any advice will be gratefully received.

many thanks,
Dave.

Post by **regent** » 19 Mar 2012, 12:33

Crankshaft speed sensor may 'ring' with the correct resistance but the ECU may still not see pulses from it (if the sensor is out of position or damaged) or due to a wiring fault.

Other than that, a fauly MAF sensor could not cause loss of spark.

themonkeypeas · Post by **themonkeypeas** » 19 Mar 2012, 14:21

Hi Regent,

Thanks for the reply, I worked that out about the MAF after I'd tested but I was was out of other ideas at the time.

In terms of the crankshaft sensor, is there any way of testing the output signal without a break-out box that you know of?

Dave.

Post by **regent** » 19 Mar 2012, 17:13

Dave,
One of the workarounds will be to use a scope, but I think this method (found it on our foums) would help you: https://www.matthewsvolvosite.com/forums ... =1&t=35244
Thanks,

themonkeypeas · Post by **themonkeypeas** » 20 Mar 2012, 11:19

Hi Regent,

Thanks for the link, Cam and crank position sensors have both checked out ok. I found an entry on another forum where someone else was getting the exact same readings as me from the Coil and Power stage connectors and they changed the ECU which resolved the issue. I've found one at a reasonable price but not sure how important the numbers on the unit are.

Is it just the Bosch 0 280 000 955 (956) number that I have to match or are the barcode numbers on top of the unit important? Also, will a second hand uunit need reprogramming with the security codes for the car?

Thanks for any help.
Dave.

Post by **regent** » 20 Mar 2012, 14:17

Dave,
The ECU may definitely be at fault but it is not a high failure rate unit.
Swapping a known good ECU is the quicker approach (if you are not paying for one).

Now this may sound dumb enough, but before I condemn the ECU, I would eliminate a possible wiring fault completely, such as grounded/pinched/shorted wires, recessed or corroded pins or loose crimps (ring zero Ohms straight from ECU pins to sensor pins or put the scope on the ECU pins to see if wave pattern remains the same like what I saw at the sensors.)

Might save you a buck, and I sincerely hope that you will find a wiring fault!

themonkeypeas · Post by **themonkeypeas** » 21 Mar 2012, 08:57

Goood plan regent, I've tried searching but can't find a pinout map for the ECU socket. Any ideas where I can get one?

Thanks,
Dave

themonkeypeas · Post by **themonkeypeas** » 22 Mar 2012, 09:19

Right, Ive found the wiring diagrams and finally managed to understand what I was looking at. My car has the LH-Jetronic 3.2 fuel injection module and the EZ 129 K ignition module as far as I can tell and I've checked out continuity on every cable going to both and that the correct signals are getting to the ECU's.

Just ordered a second hand ECU (ignition module) from ebay for £18 so hopefully that will solve the issue! I'll post on here if it does resolve it, fingers crossed.

lovevolvosalot · Post by **lovevolvosalot** » 22 Mar 2012, 19:28

I am so happy that I found this thread! It's scary exactly how similar our problems are, I have literally tested everything that you listed above and to no avail.. I kid not, our problems are exactly identical! I'm very excited to see how an ECU swap works out for you because that is the only thing I could resolve myself.. so I have my fingers crossed as well!

themonkeypeas · Post by **themonkeypeas** » 25 Mar 2012, 08:55

Right, ECU arrived, installed in car (30 secs), turned key and car fired and ran instantly. The Beige Flash rides again!

I had read on another forum that someone else was getting the same incorrect test results as me which were:
Ignition coil terminal 1 (blue wire) to ground (starter turning): 6.8 volts (should be 0.7 to 1.3 volts)
Coil power stage connector terminal 4 (starter turning): 0.3 volts (should be 0.7 to 1.3 volts)
and they said that they replaced the ECU to solve it so if you have these same readings, that is the problem. I have opened the old ECU to look for any obvious signs of damage but cannot find anything.

Since I now have it running however, the ABS light is on and the speedometer isn't working!! Looks like I've forgot to reconnect something somewhere!

Hope this is of use to you lovevolvosalot and to others out there, many thanks for your help Regent.

Dave.