Weird Speedo behaviour in a friend's 940 at startup

[AllHailKingVolvo]

Hi all,
A friend of mine has an early 940 and we're troubleshooting some running issues. It has just had a new dizzy cap and rotor plus fresh plugs and Bougicords, and after pulling fuse 1 it seems to be settling down to run better.

The real foxer of an issue is that the Speedo seems to behave really oddly at startup-when the ignition is turned to P2 prior to firing the engine, the Speedo needle arbitrarily leaps up to 30/40mph or so, and when the car is started (stationary) it seems to jump around randomly. When it gets to around 30mph on the road, it suddenly settles and works as normal.

A very random thought, but could this have anything to do with the odd running he has been experiencing if it's an electrical issue?

The car is also pumping out an unusual amount of white smoke at idle. I suspect a dodgy coolant temp sensor causing a rich condition (my 940 did similar, new CTS and it's cured), but it's also in the back of my mind that it might be a weeping HG as it's been a bit lumpy prior to doing the downline ignition refresh. Any thoughts on this would be much appreciated!

Phil

[bluebrickrick]

I've had the same, sitting on the lawn in neutral at 80 is much more relaxing than far lower speed on the Norwich 'orbital'

Draw the instrument panel out, secure all screws in the membrane type PCB at the back.

If no better, de solder (removing old solder with a solder sucker or desoldering 'wick' then resolder all the joints on the PCB.

If a Yakuzi cluster and this doesn't solve the problem there are several articles and threads about removing the speedo unit, dismantling it and replacing the capacitors which fail.

Before it fails entirely make a truth table of speed against revs in the different gears so you can use the tacho when in a speed restricted zone.

[Laird Scooby]

What Rick just said! ^^^^^

As for the steam, get the fuel tank contents down to about 1/4 tank or less then add :

https://www.toolstation.com/methylated-spirit/p99550

to the fuel tank. From your description, it sounds as if it's suffering condensation in the tank and if it has been sat for a while before your friend got hold of it or at least not used very much, that's highly likely!

Also what fuel is he running it on?

[AllHailKingVolvo]

Thanks gents! I've passed on your expertise to him. It's his first Redblock and he's a bit exasperated by the fact it's giving him issues. It's an early NA 940 with a B200F in it, so a pretty short list of troubleshooting possibilities!

[Laird Scooby]

Originally Posted by AllHailKingVolvo

Thanks gents! I've passed on your expertise to him. It's his first Redblock and he's a bit exasperated by the fact it's giving him issues. It's an early NA 940 with a B200F in it, so a pretty short list of troubleshooting possibilities!

Forgot to say Phil, about the prtrol, now we're running ethanol petrol mix, the water content in the fuel is higher and tends to show up as steam when cold. Also unleaded generally has a higher water content than leaded fuel, noth that we can get that these days of course.

White smoke is caused by oil burning by itself, for example when the tubo bearings/seals have failed and oil is being squirted into a hot exhaust and self-ignites.

A rich mixture is shown by black smoke and blue smoke signifies oil being burned with petrol (or diseasel if it's one of those horrible things! ) so points to worn pistons/rings, valve guides and/or seals.

Steam when cold is usually nothing to worry about as long as it clears once warm/hot because of the increased water content in the fuel.

If your mate is running on Tesco, Shell, Esso he's likely to get more steam when cold than if running on BP so might be worth mentioning that to him as well. Also as you probably know, i used to use Sainsburys petrol as BP used to supply them. Since Nectar points disappeared from BP to Esso, it seems Esso are supplying Sainsburys and my economy dropped horrendously to 14mpg!

A few fill ups on BP and i'm back up to about 20-23mpg, not quite got there yet as there will still be a small amount of Esso/Sainsburys in the tank but it's getting better. It always used to do 25-26mpg on my normal running but one thing that has improved is there is less steam out of the tailpipes when cold!

[360beast]

Originally Posted by Laird Scooby

Forgot to say Phil, about the prtrol, now we're running ethanol petrol mix, the water content in the fuel is higher and tends to show up as steam when cold. Also unleaded generally has a higher water content than leaded fuel, noth that we can get that these days of course.

White smoke is caused by oil burning by itself, for example when the tubo bearings/seals have failed and oil is being squirted into a hot exhaust and self-ignites.

A rich mixture is shown by black smoke and blue smoke signifies oil being burned with petrol (or diseasel if it's one of those horrible things! ) so points to worn pistons/rings, valve guides and/or seals.

Steam when cold is usually nothing to worry about as long as it clears once warm/hot because of the increased water content in the fuel.

If your mate is running on Tesco, Shell, Esso he's likely to get more steam when cold than if running on BP so might be worth mentioning that to him as well. Also as you probably know, i used to use Sainsburys petrol as BP used to supply them. Since Nectar points disappeared from BP to Esso, it seems Esso are supplying Sainsburys and my economy dropped horrendously to 14mpg!

A few fill ups on BP and i'm back up to about 20-23mpg, not quite got there yet as there will still be a small amount of Esso/Sainsburys in the tank but it's getting better. It always used to do 25-26mpg on my normal running but one thing that has improved is there is less steam out of the tailpipes when cold!

I wondered my Fabia has been running a bit rough and MPG in mid 40's not mid 50's! I've filled up with Texaco this morning as I suspected the fuel so hopefully that will start to improve things.

[Laird Scooby]

Originally Posted by 360beast

I wondered my Fabia has been running a bit rough and MPG in mid 40's not mid 50's! I've filled up with Texaco this morning as I suspected the fuel so hopefully that will start to improve things.

You've also had your Fabia laid up a fair while as well, haven't you Luke? Try draining the water out of the fuel filter (should be a drain tap on the bottom of the filter) and see if things improve.

[360beast]

Originally Posted by Laird Scooby

You've also had your Fabia laid up a fair while as well, haven't you Luke? Try draining the water out of the fuel filter (should be a drain tap on the bottom of the filter) and see if things improve.

Thanks Dave I'll give it a go.

Yeah 18 months it has been sat, done nearly 3k miles in 2 months though.

Newest fault is I believe a sticky handbrake mechanism (discs not drums) as after being in stop start traffic when I speed up to about 20mph it starts making a very strange humming noise that gets louder and faster as I speed up, slightly pull the handbrake on and it disappears.

Anyway ignore me, enough about modern sh1te and back to real cars.

[Laird Scooby]

Originally Posted by 360beast

Thanks Dave I'll give it a go.

Yeah 18 months it has been sat, done nearly 3k miles in 2 months though.

Newest fault is I believe a sticky handbrake mechanism (discs not drums) as after being in stop start traffic when I speed up to about 20mph it starts making a very strange humming noise that gets louder and faster as I speed up, slightly pull the handbrake on and it disappears.

Anyway ignore me, enough about modern sh1te and back to real cars.

Sounds very like a sticky caliper through lack of use Luke. A clean and grease of the slides, clean the edges of the pads etc should see it right.

[WUMPSTER]

agrees mine has just been sat for 3 months only and i had to re grease all the calipers and hand brake system