Overheated 940 won't re-start

[HenryM]

My poor 940 SE Turbo has been completely fantastic to me over the last four months. I've been working on a mad project in London, 7 days a week with only 3 days off over Christmas. My journey from Hastings to London every day has put a lot of miles on the old girl in a very short space of time, 21K to be precise and I have not had time to carry out maintenance other than topping things up and the odd car wash.
About 8 weeks ago I spotted a leak from the radiator which turned out to be a split on a seam near the bottom. When driving early in the morning the leak would only manifest its self when cooling down at rest. If I topped it up before going home in the evening/night the split would seem to have contracted far enough to hold water so I didn't bother rushing out to buy another rad immediately, not that I'd have had the time to do that.
Now the job is over and I have time, typically the leak has decided to open up and the other night I had the first over-heat while driving. Luckily I noticed the gauge rising and stopped to add water ASAP.
Naturally there was a lot of boiling and steaming as I added the water but once full up again the old girl started up and I got home fine.
Now she won't start!!!
There's no sign of mixing of oil and water which leads me to believe the head gasket has not been damaged. The water in the header tank is clean and typically the rad is not leaking now.
Good sparks from all the plugs and no signs of damage to them.
The fuel pump is audible and I have half a tank of fuel.
I tried some easy start in the inlet but still no life.
Has anyone got any clues that might help bring my engine back to life?
Help would be much appreciated as this car has a lot of life left in it.

[typhoon]

Replace the head gasket.

Regards, Andrew.

[HenryM]

Thanks for your rapid reply Typhoon but I'm not going to be that rapid about taking the head off without a little more diagnostics.
Compression seems to be normal though I am only judging this by the way the engine and starter motor normally sound when cranking over.
I've just found the flywheel sensor lead to be cracked. It's the old yellow banded type. Could this be causing the fuel pump to switch off when I try to crank. It's likely that the excessive heat from the engine could have caused this component or the lead to fail. I'll try a replacement tomorrow when the shops reopen and see if it's the culprit.

[niloc]

I would start by looking for fault codes: http://www.volvoclub.org.uk/faq/EngineOBDCodes.html

If you have a multimeter, you can check that the flywheel sensor is giving an output. Failure of that sensor though will prevent the pumps from starting.
I had a car with the exact same fault. All I had to do to get it going was wiggle the lead a bit until I gained a replacement.

[HenryM]

Thanks for that niloc. I had never read the codes before and after following your link I've checked everything through as instructed only to find that everything appears normal. The speed sensor is working correctly according to the code.
Now I'm stumped. I so don't want to have to change the head gasket. My mechanical skills are quite sufficient to do it but I feel there is something else I should try before getting drastic.
A compression test would surely tell me if there's a problem with the head gasket.
Given that the car started again after over heating immediately after I'd added more water I find it strange that it won't start now. Can anyone else think of something worth trying to revive my engine?

[motorhommmer]

try disconnect maf and then start it

[motorhommmer]

Meant to ask is she turning over ok ? Just not firing ??

[HenryM]

She turns over fine but will just not start.

Since last post I have not done a lot as I have been feeling under the weather. It has been suggested by a Volvo dealer that the engine temperature sensor might be damaged causing the system to try to run rich but if it's not even starting I doubt this is the problem.
What is the MAF you suggest?

[motorhommmer]

On right hand side near air box. Other thing to do is to disconnect the battery, make sure you have the radio codes. When you disconnect that will hopefully reset engine managment etc.
Bit of hit and miss here, but easy to try and might kick it in.
Brian

[niloc]

Temp sensor would cause it. Check the connections to it. Symptoms I had when I had a temp sensor fault - it would turn over, try and start (after a time), then drop back onto the starter. Turned out I had a wire come out of a crimp near the sensor.