940 LPT 2.3 problems starting in damp

[griston64]

Originally Posted by Laird Scooby

I've not heard that description before but it fits and yes.

I'm seriously wondering if you've got a loose HT lead or worse still (harder to find) a broken one that is causing this.

That's what I was thinking

[haymitch]

Hmm...the spark plug leads were replaced in November as part of the first attempt to solve the problem along with the distributor cap and the spark plugs themselves. Does the lead from the ignition coil count as an HT lead as well?

[haymitch]

I'll check that they are attached properly tomorrow though Would I test the spark plug wires themselves with a multi-meter?

[Laird Scooby]

Originally Posted by haymitch

Hmm...the spark plug leads were replaced in November as part of the first attempt to solve the problem along with the distributor cap and the spark plugs themselves. Does the lead from the ignition coil count as an HT lead as well?

Yes, it does - not only does it count, but it is the most important one and called the King or Crown lead! It also does 4 times the mount of work as the others so the chances of it failing are 4 times higher! Also, it is the only one where the ends aren't fixed on the engine - one end is on the dizzy cap, the other is on the coil which is on the body so has more movement to deal with than the others.

As you can see, there are a lot more reasons for it to potentially fail than the other 4 leads. It should have been replaced with the others but if it wasn't or has come loose because it wasn't pushed all the way home, that could well be your problem!

[haymitch]

Ah, I didn't realise that. I had a look at the leads this morning and it turns out the lead from the coil to the distributor has been replaced as well. It's got the same markings and branding as the other leads that were replaced in November.

I took the car to the garage this morning, so I'll see what he says on Monday. He said that it might be a difficult one to diagnose though as I've already tried a lot of the usual things that cause failure so I might be back to square one early next week. The only other thing I can think of is the ignition coil and the maf sensor, but it runs fine once it has got going.

I also can't help but wonder whether the fuel pump relay or coolant temperature sensor have gone again - but I don't want to start throwing parts at it.

[Laird Scooby]

The fuel pump relay appears to be working - if it wasn't then the pumps wouldn't run.

However all of the evidence is pointing to lack of cold start enrichment. Worth checking your air filter to see if it's dirty, if so, renew it and once renewed, pull fuse #1 for a couple of minutes and then refit it.

Sounds counter-intuitive as a blocked air filter will cause rich running, however this will cause the ECU to alter the fuel trims and make the mixture leaner. For a cold start, it will still enrich the mixture but as a function of how much fuel it decided was needed to run correctly at hot idle. If it has reduced this amount because of a blocked air filter, the cold start enrichment will also be reduced, hence the starting fluid getting it going.

Out of interest, how much meths did you add to the tank in one go a few months ago and what fuel do you usually run on?

[haymitch]

I added four litres of meths and the tank was around 2 / 3 full. The car did get seem to get better after I added it (this was the same time that the coolant temperature sensor was replaced as well though).

I have a spare air filter handily- I got two for the price of one when I bought one off eBay fairly recently. I will try replacing it when I get the car back

[Laird Scooby]

That's the right proportion of meths but it might be worth adding say 2L when the level gets down to about 1/4 tank, sometimes if the first lot doesn't get rid of all the condensation it returns a few months later - pain in the Aristotle but does happen.

I'm not ruling out the CTS, i renewed mine some months back with a pattern one but not entirely convinced it's right so i also may have to bite the bullet and get a Bosch one.

If you do swap your air filter, don't forget to pull fuse #1 before you change the air filter and replace it after - this resets the ECUs fuel trims back to factory so gives you a "level playing field" to start from.

[haymitch]

Sounds good, will buy some meths in preparation in that case! As is sods law I filled up the tank just before the problem started happening. You asked which petrol I used, it was premium but I've switched to normal grade petrol recently.

One final question, I started it with holts ether starter fluid this morning to get it to the garage. Will that be an okay interim measure to get it started or will this cause harm at some point?

[Laird Scooby]

Originally Posted by haymitch

Sounds good, will buy some meths in preparation in that case! As is sods law I filled up the tank just before the problem started happening. You asked which petrol I used, it was premium but I've switched to normal grade petrol recently.

One final question, I started it with holts ether starter fluid this morning to get it to the garage. Will that be an okay interim measure to get it started or will this cause harm at some point?

That tends to point to it being petrol which is quite ironic, purely because of the coincidence! What brand of petrol? Please don't say Tesco!

Eventually ether can cause problems, used as a "once in a while emergency/diagnosis measure" it shouldn't but there was a "myth" that engines could become addicted to it.

I say "myth" as there was some truth in it but only metaphorically - what happened was prolonged use of ether, because of its high volatility, bent the piston rings causing reduced compression. This meant after long-term use to start the car, it no longer had the compression it needed to actually start running by itself. As such, it then needed ether every time so in effect, was addicted to it!