240 General: New (to me) 1980 Volvo 244

[Laird Scooby]

Originally Posted by Othen

Good morn Dave,

It does seem odd that a leaner mixture might reduce fuel economy - but I suppose that is just an unintended consequence of electronic control systems. I hope that has solved your issue - 27 MPG is a good result for such a big car.

Stay safe,

Alan

Not just electronic control systems Alan, even on carb engines it can increase fuel consumption as the engine has to work harder and the leaner mixture results in more unburned fuel, increasing the HC content as well as consumption.
By having to open the throttle wider on a "tradiitional engine", you decrease the available inlet manifold vacuum. In turn, this reduces the vacuum available at the vacuum port on the carb, thus retarding the ignition timing.

Before this happened, i was consistently able to get 30+mpg on any sort of open road running and on one particular trip across the Fens (so definitely not good A roads, a lot of up and down through the box but some reasonable long stretches of smooth, straight roads too) i managed a shade over 37mpg from it.

In addition to the adjustment i made to the CO several months ago, two other things happened. First, i replaced the back axle as the original was knackered. The original was a 3.91:1 ratio, the replacement is 3.54:1 so about 10% higher ratio.
In theory this should improve economy and it's made cruising more relaxed for sure.

However there was another side effect not considered. For 1988MY, the 760 (and other 7xx with ABS) used a 96 tooth reluctor ring for the speedo drive and also for the ABS system with 96 tooth rings on each front hub as well.
As the replacement axle was from a 1995 940, that uses a 48 tooth reluctor ring in the back axle. I'd been led to believe (from information found online) it was only the back axle on mine with a 96 tooth ring, i'd overlooked the fact that the front hubs also had 96 teeth rings. As such since sorting the speedo (speedos of the time used a 12 tooth ring for non-ABS cars) converter to only divide by 4 instead of 8 to give the correct speed readout, i've been looking in the wrong area to solve the problem of the ABS light coming on.

During ABS light operation (signifying a fault in the ABS system) the ABS system is disabled and i've suspected that somewhere within the system, there is a pressure lock of some description causing a bit of brake binding/drag across all 4 wheels. This might also be enough to impact the economy badly.

However, i now have a pair of front 48 tooth rings (and i've already updated the ABS ECU to a 1991 spec unit to expect 48 tooth ring inputs) that i'm waiting on a 36mm socket so i can remove the front hubs and swap the rings over.
In between whiles, the O/S/F ABS sensor failed so that's new, i just hope the N/S/F sensor isn't on it's way out as well!

Hopefully then there shouldn't be any suspicion on the brakes (as the ABS should be working as intended) binding and if the economy is still poor, it leaves me with one other sneaking suspicion, that' of a loose baffle in the exhaust middle box. This is the only part of the exhaust system that i haven't replaced and the only part that actually has baffles now.

I also have an adaptor i've made up with a Lambda boss i welded into it to fit to the front pipe which is primarily for the LPG system i plan on fitting. However i should be able to jerry rig some sort of meter/display to indicate whether it's running rich, lean or near stoichiometric.
I need to deburr the adaptor and drill a 20mm hole in the front pipe to fit it but i have some Lambda sensors around (used but functional) so should be able to sort some sort of indication. If my 36mm socket doesn't turn up today, i might get on with that.

I did say it was a long story!

[Othen]

Originally Posted by Laird Scooby

Not just electronic control systems Alan, even on carb engines it can increase fuel consumption as the engine has to work harder and the leaner mixture results in more unburned fuel, increasing the HC content as well as consumption.
By having to open the throttle wider on a "tradiitional engine", you decrease the available inlet manifold vacuum. In turn, this reduces the vacuum available at the vacuum port on the carb, thus retarding the ignition timing.

Before this happened, i was consistently able to get 30+mpg on any sort of open road running and on one particular trip across the Fens (so definitely not good A roads, a lot of up and down through the box but some reasonable long stretches of smooth, straight roads too) i managed a shade over 37mpg from it.

In addition to the adjustment i made to the CO several months ago, two other things happened. First, i replaced the back axle as the original was knackered. The original was a 3.91:1 ratio, the replacement is 3.54:1 so about 10% higher ratio.
In theory this should improve economy and it's made cruising more relaxed for sure.

However there was another side effect not considered. For 1988MY, the 760 (and other 7xx with ABS) used a 96 tooth reluctor ring for the speedo drive and also for the ABS system with 96 tooth rings on each front hub as well.
As the replacement axle was from a 1995 940, that uses a 48 tooth reluctor ring in the back axle. I'd been led to believe (from information found online) it was only the back axle on mine with a 96 tooth ring, i'd overlooked the fact that the front hubs also had 96 teeth rings. As such since sorting the speedo (speedos of the time used a 12 tooth ring for non-ABS cars) converter to only divide by 4 instead of 8 to give the correct speed readout, i've been looking in the wrong area to solve the problem of the ABS light coming on.

During ABS light operation (signifying a fault in the ABS system) the ABS system is disabled and i've suspected that somewhere within the system, there is a pressure lock of some description causing a bit of brake binding/drag across all 4 wheels. This might also be enough to impact the economy badly.

However, i now have a pair of front 48 tooth rings (and i've already updated the ABS ECU to a 1991 spec unit to expect 48 tooth ring inputs) that i'm waiting on a 36mm socket so i can remove the front hubs and swap the rings over.
In between whiles, the O/S/F ABS sensor failed so that's new, i just hope the N/S/F sensor isn't on it's way out as well!

Hopefully then there shouldn't be any suspicion on the brakes (as the ABS should be working as intended) binding and if the economy is still poor, it leaves me with one other sneaking suspicion, that' of a loose baffle in the exhaust middle box. This is the only part of the exhaust system that i haven't replaced and the only part that actually has baffles now.

I also have an adaptor i've made up with a Lambda boss i welded into it to fit to the front pipe which is primarily for the LPG system i plan on fitting. However i should be able to jerry rig some sort of meter/display to indicate whether it's running rich, lean or near stoichiometric.
I need to deburr the adaptor and drill a 20mm hole in the front pipe to fit it but i have some Lambda sensors around (used but functional) so should be able to sort some sort of indication. If my 36mm socket doesn't turn up today, i might get on with that.

I did say it was a long story!

... but actually quite an interesting story Dave. Diagnosing what is wrong with machines is always satisfying (I find) when one hits upon the eureka! moment.

I have a 36mm socket here, but unfortunately Thetford is a bit too far to drop it off (that information didn't help you much - sorry).

Bits are turning up for the Royal Barge's head job: the timing belt, exhaust studs, thermostat, camshaft seal, gasket set and expansion tank cap have all arrived in the mail. I'm just waiting on the head (should be here by Tuesday) and some M6 studs.

I've just had a look at the job this morn, it doesn't look too tricky, but my main concern is bolts and studs breaking - they are probably all 40 years old. I've given the crank pulley bolts and exhaust manifold nuts a spray with some release oil, and I'll repeat that a few times. If nothing breaks and I don't need any valve shims I should be able to get it all done in a day towards the end of next week.

I'm looking forward to getting the RB back on the road (well, it runs and rides now, it just isn't worth taking a risk if I don't need to.

Stay safe.

[Laird Scooby]

Originally Posted by Othen

... but actually quite an interesting story Dave. Diagnosing what is wrong with machines is always satisfying (I find) when one hits upon the eureka! moment.

I have a 36mm socket here, but unfortunately Thetford is a bit too far to drop it off (that information didn't help you much - sorry).

Bits are turning up for the Royal Barge's head job: the timing belt, exhaust studs, thermostat, camshaft seal, gasket set and expansion tank cap have all arrived in the mail. I'm just waiting on the head (should be here by Tuesday) and some M6 studs.

I've just had a look at the job this morn, it doesn't look too tricky, but my main concern is bolts and studs breaking - they are probably all 40 years old. I've given the crank pulley bolts and exhaust manifold nuts a spray with some release oil, and I'll repeat that a few times. If nothing breaks and I don't need any valve shims I should be able to get it all done in a day towards the end of next week.

I'm looking forward to getting the RB back on the road (well, it runs and rides now, it just isn't worth taking a risk if I don't need to.

Stay safe.

I don't know what releasing oil you're using Alan but invest in some acetone (aka nail varnish remover) and some Carlube ATF-U and make a 50/50 mix. Keep it sealed between uses to prevent the acetone evaporating and shake well before each use as they have a tendency to separate.

Brush, spray, squirt or otherwise get it onto the threads of the fasteners and let it soak. You'll be amazed how easily things come apart, especially after a few days soaking and a couple of repeated appliactions in between whiles.

Besides the fact it's earned the nickname of WMP - Weapon of Mass Penetration, it has proved its worth many times with countless fasteners including severely overheated and corroded turbo mounting nuts/bolts that hadn't been touched in their 20 year life, various exhaust studs/nuts other than that and even an accidental proof of its derusting capability when i sprayed some on a pantograph assembly i made as part of something else and needed to repurpose part of it. I'd sprayed the bolts i need to remove and the rest of the mechanism got splashed with overspray. That was 2-3 years ago and despite leaving the thing in the open (as it had been for some time before) it's still possible to see where it was splashed with WMP - although the rust is creeping back after this amount of time, it's much less severe on those spots than elsewhere.

When removing the studs, use the "back and forth" method to minimise the chances of shering and/or seizing. Once you start removing the stud, there's likely to be a point when the thread starts going tight. Give the thread some lube (either WMP or your old release oil) and retighten the studs, then undo it again to the same point where it begins to get stiff again. Then literally turn the fastener back and forth in a total of about 1 turn (half a turn each way) a few times until it shifts. You may have to do this a few times during removal of a stud/bolt/nut but it's quicker, easier and less stressful than having to remove a broken fastener!

It's a time-honoured method that has rarely failed me and was a tip given to me more years ago than i can remember. Don't be tempted to keep winding a thread when it's almost out and goes stiff, chances are it will shear then. Use this method and there's every chance you'll get it out intact!

Good luck with the head job, looking forwards to loads of pics and a good write up and as always, if you run into problems, just ask!

[Laird Scooby]

Originally Posted by Othen

... but actually quite an interesting story Dave. Diagnosing what is wrong with machines is always satisfying (I find) when one hits upon the eureka! moment.

I have a 36mm socket here, but unfortunately Thetford is a bit too far to drop it off (that information didn't help you much - sorry).

Forgot to say thanks, i realised i needed another 36mm socket (i used to have one as part of a 3/4 drive socket set i sold) so have ordered one and waiting on Hermes to deliver it sometime soon.

The proof of the pudding on the economy will be in a few days time when i give it a drink of BPs finest Ultimate Unleaded, last fill up showed 16-17mpg so hoping a slight improvement is shown although it will be slight as only got a few days to make a difference, the real difference will show up over the next few weeks.

Or not as the case may be!

[Othen]

Originally Posted by Laird Scooby

I don't know what releasing oil you're using Alan but invest in some acetone (aka nail varnish remover) and some Carlube ATF-U and make a 50/50 mix. Keep it sealed between uses to prevent the acetone evaporating and shake well before each use as they have a tendency to separate.

Brush, spray, squirt or otherwise get it onto the threads of the fasteners and let it soak. You'll be amazed how easily things come apart, especially after a few days soaking and a couple of repeated appliactions in between whiles.

Besides the fact it's earned the nickname of WMP - Weapon of Mass Penetration, it has proved its worth many times with countless fasteners including severely overheated and corroded turbo mounting nuts/bolts that hadn't been touched in their 20 year life, various exhaust studs/nuts other than that and even an accidental proof of its derusting capability when i sprayed some on a pantograph assembly i made as part of something else and needed to repurpose part of it. I'd sprayed the bolts i need to remove and the rest of the mechanism got splashed with overspray. That was 2-3 years ago and despite leaving the thing in the open (as it had been for some time before) it's still possible to see where it was splashed with WMP - although the rust is creeping back after this amount of time, it's much less severe on those spots than elsewhere.

When removing the studs, use the "back and forth" method to minimise the chances of shering and/or seizing. Once you start removing the stud, there's likely to be a point when the thread starts going tight. Give the thread some lube (either WMP or your old release oil) and retighten the studs, then undo it again to the same point where it begins to get stiff again. Then literally turn the fastener back and forth in a total of about 1 turn (half a turn each way) a few times until it shifts. You may have to do this a few times during removal of a stud/bolt/nut but it's quicker, easier and less stressful than having to remove a broken fastener!

It's a time-honoured method that has rarely failed me and was a tip given to me more years ago than i can remember. Don't be tempted to keep winding a thread when it's almost out and goes stiff, chances are it will shear then. Use this method and there's every chance you'll get it out intact!

Good luck with the head job, looking forwards to loads of pics and a good write up and as always, if you run into problems, just ask!

Many thanks Dave,

I have acetone and ATF in the garage, I'll mix up an egg cup full when I've posted this and brush it on to the 2 or 3 places I'm concerned about.

Stay safe.

[Stephen Edwin]

Originally Posted by Laird Scooby

The trucks might have huge tanks but they also have a voracious thirst - 7mpg is a good average for most trucks, 4-6mpg probably more normal so the range is only about 500 miles on a 100 gallon tank. That means at some point they will need to fill up over here so they don't get a "free pass" as it were.

And in the balance. How many journeys of 500 miles begin with a full 100 gallon tank?
Total revenue lost to the UK equals how much?



The fuel duty playing field is likely to be as level as a fisheries policy.


.



.

[Othen]

Originally Posted by Laird Scooby

Forgot to say thanks, i realised i needed another 36mm socket (i used to have one as part of a 3/4 drive socket set i sold) so have ordered one and waiting on Hermes to deliver it sometime soon.

The proof of the pudding on the economy will be in a few days time when i give it a drink of BPs finest Ultimate Unleaded, last fill up showed 16-17mpg so hoping a slight improvement is shown although it will be slight as only got a few days to make a difference, the real difference will show up over the next few weeks.

Or not as the case may be!

16 MPG - ouch!

Stay safe.

[Laird Scooby]

Originally Posted by Othen

16 MPG - ouch!

Stay safe.

Fortunately 95% of my Volvo use is as a Dogmobile so short runs only. However when i use the Volvo for a monthly shop and to fill up, it gets painful as the monthly shop involves a trip to Thetford, some 12 miles or so away.

My first real alert was when it was struggling to return 14mpg on Sainsburys petrol - this was soon after Nectar points disappeared from BP and moved onto Esso. Before Esso had Nectar points, they had Tesco Clubcard points and when i had previously used Esso in the Volvo, i'd been lucky to see 20mpg from it so assumed this was the sole cause of the economy problems.
Changing to BP Ultimate from Sainsburys/Esso saw it rise to 16mpg or so, about a 15% improvement so obviously there was still a problem. In the meantime i'd checked all the usual areas for leaks plus a few more and still nothing found.

Been a long slow process!

[Othen]

Originally Posted by Laird Scooby

Fortunately 95% of my Volvo use is as a Dogmobile so short runs only. However when i use the Volvo for a monthly shop and to fill up, it gets painful as the monthly shop involves a trip to Thetford, some 12 miles or so away.

My first real alert was when it was struggling to return 14mpg on Sainsburys petrol - this was soon after Nectar points disappeared from BP and moved onto Esso. Before Esso had Nectar points, they had Tesco Clubcard points and when i had previously used Esso in the Volvo, i'd been lucky to see 20mpg from it so assumed this was the sole cause of the economy problems.
Changing to BP Ultimate from Sainsburys/Esso saw it rise to 16mpg or so, about a 15% improvement so obviously there was still a problem. In the meantime i'd checked all the usual areas for leaks plus a few more and still nothing found.

Been a long slow process!

Have you done a compression test Dave? As a bike guy (and particularly for 2 strokes) I know it is a good place to start, and will either eliminate or indicate mechanical problems.

Stay safe.

[Laird Scooby]

Originally Posted by Othen

Have you done a compression test Dave? As a bike guy (and particularly for 2 strokes) I know it is a good place to start, and will either eliminate or indicate mechanical problems.

Stay safe.

Not recently Alan. No real reason to do one to be honest although i see your line of thought on it.
Given the vast improvement in power and torque since tweaking the mixture back to where it should be, i'm pretty confident i've found the problem but obviously time will tell.