940 LPT 2.3 problems starting in damp

[Laird Scooby]

On the hot start, try turning the key to the start position and releasing immediately the starter makes contact with the engine. You should hear the fuel pumps running for a second or two after. Then try starting normally, if things improve, then you may need to look at the FPR (Fuel Pressure Regulator) and/or the vacuum hose supplying it.

It could also be the check valve on the main fuel pump outlet, that would allow fuel pressure to drop allowing it to also vapourise which in the heat we currently have would happen easily.

Try the "starter flick" as described above, see how you get on - if that doesn't work, we'll try the "flooded engie procedure" instead.

[haymitch]

Sounds good, I'll give that a try - thanks How does that trick work? I'm guessing it allows a little bit more fuel to reach the injectors so that when I try to start properly the fuel pressure is slightly greater?

[Laird Scooby]

Originally Posted by haymitch

Sounds good, I'll give that a try - thanks How does that trick work? I'm guessing it allows a little bit more fuel to reach the injectors so that when I try to start properly the fuel pressure is slightly greater?

More or less along the right lines there but the idea is, if the fuel has vapourised in the fuel rail, there won't be any fuel pressure. The injectors are just valves - taps if you like - that open or shut by an electrical impulse. If you lose fuel pressure, you'll inject nothing and it can take a while to rebuild pressure if it has vapourised

By "flicking the starter", it tells the ECU the engine is being cranked so it must run the fuel pumps. As it can take a second or so for the flywheel to do a complete turn at starter motor speeds, the pumps stay running for a second or two after the starter has been stopped. This means the pumps run with no demand on them for that time, refilling and pressurising the fuel rail so that next time you try, you have full fuel pressure and no vapour locks so the engine fires.

I'm having to do the same trick on mine for cold starts at the moment due to a failed check-valve on the main pump outlet :

https://www.volvoforums.org.uk/showthread.php?t=295939

Sometimes i have to do it when it's hot as well for the same reason but because of vapour locks.

When you start from cold, does it fire almost instantly or does the starter run for a couple of seconds before it catches? IF the latter, try the same "flick the starter" trick when it's cold.

[haymitch]

Hmm...I'd say a second at most Just watched an old video of me starting the car and you can hear the starter motor about 5 times before it started.

[Laird Scooby]

Originally Posted by haymitch

Hmm...I'd say a second at most Just watched an old video of me starting the car and you can hear the starter motor about 5 times before it started.

Have you got a link to that video at all?

[haymitch]

Not at the moment - will see if I can upload it though

[haymitch]

Right, I found two videos one showing a cold start and one showing the hot start problem.

Here's the cold start: https://youtu.be/obfTWc8dZYg

Seems worse than it is now after some of the items I've replaced (the wipers don't go on everytime I turn the key - must have knocked the stalk during the video!)

Here's the hot start (sorry the video is the wrong way around - I can't work out how to rotate the video on YouTube)

https://youtu.be/Oy7f-1NC2hc

This is the worst it's been. Usually the engine has a bad idle for a while before stalling - I have to keep revving the engine. I tried the flooded engine procedure half way through the video which is why the rev counter goes wild! I try my best to rev the car gently rather than racing the engine but it's hard to do this at first.

[Laird Scooby]

Sorry, meant to respond yesterday but got sidetracked!

On the hot start, was that taken on a particularly hot day?

The cold start isn't too bad but a bit slow, takes a couple of seconds to pump the fuel through before it fires. Have you tried the "flick the starter" trick and does it fire instantly on the second turn of the key?

[haymitch]

In the video the temperature was 18 degrees C, so not a hot day really. It did start harder from cold on a hot day over the weekend. It did a less bad version of what happened in the video. The engine started but the idle was rough for 1-2 minutes before settling down. This was after I'd replaced the fuel suppression relay with the battery disconnected. So perhaps the fuel trims had been reset? A few days before it had been very bad after being driven in the morning and then restarted in the evening after being sat in the sun. Symptoms were the same as my previous video.

I tried the 'starter flick switch' today from cold during my lunch break. I've uploaded the video from today's cold start here:

https://youtu.be/3vPBCeYRMB4

[Laird Scooby]

Originally Posted by haymitch

In the video the temperature was 18 degrees C, so not a hot day really. It did start harder from cold on a hot day over the weekend. It did a less bad version of what happened in the video. The engine started but the idle was rough for 1-2 minutes before settling down. This was after I'd replaced the fuel suppression relay with the battery disconnected. So perhaps the fuel trims had been reset? A few days before it had been very bad after being driven in the morning and then restarted in the evening after being sat in the sun. Symptoms were the same as my previous video.

I tried the 'starter flick switch' today from cold during my lunch break. I've uploaded the video from today's cold start here:

https://youtu.be/3vPBCeYRMB4

Something not quite right somewhere. Can you hear the fuel pumps run after flicking the starter?