Help diagnosing a non starter

[aardvarkash10]

! - no, the cps is a sealed unit and relatively impervious to water.

2 - no danger in sticking a piece of pipe in there.

2a - supplementary: watch CLOSELY for further signs of water loss. It's possible (probable) that the overheating has warped the cylinder head and you may (will) get a gasket leak.

The temp gauge is slower than the engine's ability to damage itself unfortch.

[Laird Scooby]

Originally Posted by Casheye

So with the quote above in mind, I think I may have solved the problem but some clarification would be appreciated.

I haven't had much success with getting this solved but yesterday I took a drive up to Dartmoor and on the way home, the temp guage went into the red. So I pulled over and the radiator was empty. Unfortunately (and because I'm such a good samaritan ) I'd given the 5 litre bottle of water I usually carry to someone I spotted with radiator problems the other day. So I didn't have nearly enough to top up. Phoned my breakdown company and ended up getting towed home.

This morning I went out and topped up the system and I could hear water gushing out from near the bellhousing. A quick peek and I could see that one of the necks for the heater water valve had snapped off. I've removed the old valve and dug out the old neck which was more like picking and old damp cigar out of the hose than a piece of plastic and poured some more water though the system to flush out any bits I missed.

Now am I right in assuming that the CPS has to pick up a signal before fuel is sent to the engine? If that's the case, then the likely cause of my problems has been this degrading plastic meaning that water has been leaking onto the top of the bell housing and getting the CPS wet, causing it to not work?

It would definitely explain why I'd have varying degrees of success starting it when the car was parked at different angles as the water wouldn't drip straight down onto the sensor.

I'll need to order a new valve, but the only place I can find one for sale is on the eurocarparts ebay site. I can't find it on their main website and delivery is a week away. So if anyone has a spare for sale, let me know.

What do you guys think as to this being the sole cause of my starting issue?

Also, on a side note... what's the danger in bypassing this valve temporarily with a straight bit of pipe?

Thanks in advance.

First it was a blessing in disguise you'd given your 5L of water away! It did the other motorist some good but would have done you no good at all as it would have come straight out the broken heater valve, possibly after cracking the block (through thermal shock) on the way through.

If you ever need to add cold water to a hot engine, firstly leave the engine idling and secondly trickle the water in slowly - this minimises the thermal shock as the "new" water has time to mix with the hot water (hopefully) before hitting the block.

As a temporary measure, you can bypass the heater valve with a short piece of 15mm domestic copper pipe - everything will work normally except the coldest setting on the heater, this will still slightly warm the incoming air. If you have air-con as i suspect you have, you probably won't notice this anyway.

https://www.ebay.co.uk/itm/9447896-1...s/283895334839

I found 22 results on ebay for a "Volvo 940 heater valve" including the ECP one. It is listed on their site but you have to use their own part number (212660010) to find it.

https://www.eurocarparts.com/p/eis-h...alve-212660010

No prizes for guessing i've come across this anomaly before!

There's another option, a PartsMonster valve which i think is the ebay shop for PFV :

https://www.ebay.co.uk/itm/Volvo-Hea...0/283864415256

Whichever you choose, you can get by with the copper (or other 15-16mm O/D pipe for now until it arrives.

As for your theory of the coolant making the CPS wet and causing it to not operate, i don't wish to pour cold water (or hot coolant ) on your theory but i suspect it might be a slight red herring as the liquid should, in theory at least, evaporate off while driving.
However that doesn't account for residual pressure forcing coolant out of the broken heater valve and spraying the CPS and/or the dizzy cap. A common cause of misfires, cutting out and failure to start is the screenwash T-velve on the bonnet which leaks when it fails. If the screen wash is used, it then squirts washer fluid over the dizzy cap causing shorting out of the HT voltage and ffaailure to spark correctly. It can also generate condensation inside the cap with the same result.

As such i think you may have found the problem by accident but with the wrong (or partially wrong) theory to support it. That's not suggesting you discount the CPS by the way, that could still be faulty but take it one step at a time so you'll know what the exact cause was.

You are correct in your belief the fuel pump relay won't operate (except for a brief 2 second ish pulse when the ignition is first switched on) until it gets pulses from the CPS but you need to either renew the CPS or give it and its wiring a very thorough inspection to determine whether it's faulty or not.

[Casheye]

Originally Posted by aardvarkash10

! - no, the cps is a sealed unit and relatively impervious to water.

2 - no danger in sticking a piece of pipe in there.

2a - supplementary: watch CLOSELY for further signs of water loss. It's possible (probable) that the overheating has warped the cylinder head and you may (will) get a gasket leak.

The temp gauge is slower than the engine's ability to damage itself unfortch.

I think I caught it pretty quickly because the needle dropped back down to the regular position within about half an hour of me pulling over and I didn't notice any steam coming from the rear of the car when I was driving which I've had before when a water pump broke and I didn't spot the needle going off the guage before I looked out the rear window and just saw mist

Originally Posted by Laird Scooby

First it was a blessing in disguise you'd given your 5L of water away! It did the other motorist some good but would have done you no good at all as it would have come straight out the broken heater valve, possibly after cracking the block (through thermal shock) on the way through.

If you ever need to add cold water to a hot engine, firstly leave the engine idling and secondly trickle the water in slowly - this minimises the thermal shock as the "new" water has time to mix with the hot water (hopefully) before hitting the block.

As a temporary measure, you can bypass the heater valve with a short piece of 15mm domestic copper pipe - everything will work normally except the coldest setting on the heater, this will still slightly warm the incoming air. If you have air-con as i suspect you have, you probably won't notice this anyway.

https://www.ebay.co.uk/itm/9447896-1...s/283895334839

I found 22 results on ebay for a "Volvo 940 heater valve" including the ECP one. It is listed on their site but you have to use their own part number (212660010) to find it.

https://www.eurocarparts.com/p/eis-h...alve-212660010

No prizes for guessing i've come across this anomaly before!

There's another option, a PartsMonster valve which i think is the ebay shop for PFV :

https://www.ebay.co.uk/itm/Volvo-Hea...0/283864415256

Whichever you choose, you can get by with the copper (or other 15-16mm O/D pipe for now until it arrives.

As for your theory of the coolant making the CPS wet and causing it to not operate, i don't wish to pour cold water (or hot coolant ) on your theory but i suspect it might be a slight red herring as the liquid should, in theory at least, evaporate off while driving.
However that doesn't account for residual pressure forcing coolant out of the broken heater valve and spraying the CPS and/or the dizzy cap. A common cause of misfires, cutting out and failure to start is the screenwash T-velve on the bonnet which leaks when it fails. If the screen wash is used, it then squirts washer fluid over the dizzy cap causing shorting out of the HT voltage and ffaailure to spark correctly. It can also generate condensation inside the cap with the same result.

As such i think you may have found the problem by accident but with the wrong (or partially wrong) theory to support it. That's not suggesting you discount the CPS by the way, that could still be faulty but take it one step at a time so you'll know what the exact cause was.

You are correct in your belief the fuel pump relay won't operate (except for a brief 2 second ish pulse when the ignition is first switched on) until it gets pulses from the CPS but you need to either renew the CPS or give it and its wiring a very thorough inspection to determine whether it's faulty or not.

Thanks for that.

Are there any real differences between those valves you've posted?

[Laird Scooby]

Originally Posted by aardvarkash10

! - no, the cps is a sealed unit and relatively impervious to water.

I totally agree until the point the insulation on the cables leading to it is compromised by the heat, oil, time etc Ash.

After that it can become porous to water and condensation, also we don't know if there is any dirt on the flywheel that alters state when damp, known it before on ABS sensors where they show a fault in the wet but not when dry. We know water has an effect on magnetism and gravity so while it's a long shot, it's still possible.

Originally Posted by Casheye

Thanks for that.

Are there any real differences between those valves you've posted?

As far as i can tell, all those valves are the same with different brands on them. Sadly increasingly common these days, one part is manufactured for a whole host of brands and sold at different prices according to which brand they have on them.

I should have mentioned the possibility of HGF and/or a warped head but if it's looking good, just keep an eye on things for now.