Car trouble driving me insane...start you bastard, start!

[D O G]

I am really at the end of my tether with this one, please can anyone help me diagnose the fault, as I am fast approaching a violent breakdown.

Essentially the car (Volvo 850 2litre 20V, 1994) is becoming incredibly stubborn to start. On the advice of the AA man the other day I have changed:

- Crank sensor
- Coil pack

It has made no difference.

On checking the spark from the coil to the dizzy, whilst the engine is being cranked, there is no spark, but as you stop cranking (i.e. turning the key back off) a spark appears, and looks pretty strong. Clearly the spark at this point is useless, as you have stopped cranking.

The thing is, the problem can be fairly erratic - sometimes it just starts straight-away.

My partner relies on the car as her only transport - which she needs to use to ferry my 9month year old daughter around. Its really getting me super stressed out that I cant fix it, and money is pretty tight at the moment.

I reckon I'm going to have to get a mobile mechanic out to look at it unless I can sort it, does anyone know of a good one in the Southampton/Locks Heath/Fareham area?

Really appreciate anyones help with this.

Ta

Chris

[flat spot]

Very difficult to say without checking, but if there is potentially a spark all the time, it cranks all the time, but not at the same time I'd start by checking the ignition switch and associated wires.

[Harold_Shand]

https://www.volvoclub.org.uk/

I needed their help a few times with a old 460 I had. Volvos? Reliable? Humph.
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BCF's 6th favourite poster 2009-2010

Harold_Shand's theory might be the best explanation.

[Kickstart]

Hi

Does it spark when you stop cranking, or as you turn the ignition off? Just that a coil works by discharging when the earth is interrupted, and would suspect this happens when power is cut to the ECU.

Anyway, suggests you are getting power to the coil but that the coil is not being triggered. So likely to be ECU / electronic ignition unit or the crankshaft position sensor, or the wires between them.

Is there just a single pickup? Some cars have 2 (one on the crank,one on a cam). Is there some kind of adjustment for the clearance from the sensor to the trigger?

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Kickstart]

Hi

Found this:-

https://www.volvoclub.org.uk/tech/service/850/EngineTheoryOpertion.pdf

Seems it does have a seperate crank and cam position sensor. Which have you changed?

Seems the ECU does have a self dianostic function, but not easily triggered. Whether it is a standard OBD setup and you can use a generic tester I do not know.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[D O G]

Yes I know it has a cam sensor too (after looking at my Haynes), I only changed the crank sensor (didn't know about the cam sensor at the time).

It has an onboard fault reader/display unit, which should indicate whether there is a problem with any of the sensors. It did not show a fault with any such sensors (I only found out about this once I had changed the crank sensor), but as you say it may be that the unit has not been triggered (it did show up a fault with the battery voltage being too low - not surprising really, but I believe this is an effect, not a cause - battery on charge).

I think what I will do is go and grab the cam sensor from the srappy in the morning, change that, see if it works, and if not, I'll burn it.

Thanks!