850 T5 intermittent starting

[mike 850]

Cool try that first let me know, make sure it's got a decent connection on the gearbox. You test the crank sensor with an ohmmeter, needs to be between 200-500, think they are usually 297. Camsensor gives a square wave of between 1-5v. Just to start with...

[Harvey]

Just looking you should be


Testing:
-unplug the harness going to the crankshaft located under the distributor cap (2 prong plug)
-a multimeter is required for this test
-set the ohm meter to the thousand increment setting
-put the test probes on the terminals inside the plug on the crankshaft sensor side
-the reading should be between 200-500ohms
-if the reading is not within the specified range, the sensor needs to be replaced

Matthews Volvos site.

To slow....

[Sparkysparks]

Ok, ill update this thread as and when. Thanks Mike.

[Sparkysparks]

Harvey, this was my first test. The resistance was towards the lower end of the scale so ive changed that for a brand new sensor.

[Sparkysparks]

Ok assuming all is good with the cam sensor, whats the next step, as i only get limited time with the car and id like to check as much as possible when i can.
Thanks.

[twr]

Have you tried the crankshaft sensor. If you need one i have a new one spare mate.

[mike 850]

Under what conditions does it start? or is it completely random, still possibly sounding like an earth issue. have you definitely got fuel at the rail? does it smell of fuel when you crank?

[mike 850]

Also if you can get it to start, wiggle those cables by the relay, and by the crank sensor, they could still be dodgy

[Sparkysparks]

Thanks twr, I have already put a new one on though, I tried that first.

The fuel pump is working as is the relay. I have 45psi at the rail after a prime.
I have also tried to wiggle the cables about when running and not to see if it helps.
It is completely random as far as I can tell. Although it has been useable, just not at the moment with damp weather.

[mike 850]

after its started does it stop and start fine immediately or is it still hit and miss?

[Sparkysparks]

After it starts it runs fine. It has cut out randomly once only. But then trying to start it again is hit and miss.
Sometimes it will start 10 times in a row and others it wont start ever. Sometimes it will start if cranked for up to 40 seconds, but its not a given formula. It really is intermittent.

[nottsgreent5]

Worth a mention i had a similar issue with a friends t5 a few years ago swapped the starter for another and never had a issue again i know its a stab in the dark but fixed that car

[Sparkysparks]

I have read that it might be a starter. How did you come to this conclusion?
To rule it out can I bump start it?

[mike 850]

Have you tried the earth yet? I believe tge draw from a bad earth will draw power from elsewhere

[Sparkysparks]

I tried putting the jump lead on the gearbox and negative and still nothing.

[Sparkysparks]

I have had a look at this today. Re wired the relay and nothing has changed.
What are the chances of the ecu wiping themselves?
There's a black orange wire from the relay that when earthed makes the connection for the relay. This wire goes straight to pin a41 on the ecu.

[mike 850]

Have you checked continuity on that wire?

[Sparkysparks]

Yep continuity between relay and ecu pin is fine

[mike 850]

Really odd, I remember on mine it all seemed to connect ok and all the ecu pins were fine but the draw of the starter wouldn't allow a start. I'm sure it must be something like that if it runs fine after its started, have you tried a different battery?

[Sparkysparks]

I would agree with you that the starter is the issue here but its still not connecting the relay before I crank it. Its pointing to the ECU I think.
Does anyone have a spare locally I could try?