Fuel Consumption

Post by **chrisd87** » Mon Nov 07, 2005 5:06 pm

Hi all,

I am wondering if anyone might know what's wrong with my 1098 moggy. The car itself is running fine and the performance seems relatively ok but the fuel consumption is truly awful. I calculated the other day that i'm only getting about 16-20mpg, so something is clearly wrong. At today's petrol prices I really need to get it sorted!

The car has been fitted with a brand new carb only about a month ago (problem pre-dates this), which has made no difference to the economy. I've set the mixture up with a colourtune so it's not running rich. The car has new plugs, the points are correctly set, and as far as I know the brakes aren't dragging (they're not hot after a run). The car isn't pouring out smoke, either.

Do you think that any of the following might be affecting the economy:

-Tappets haven't been set for at least 3000 miles
-Rocker cover gasket leaking oil (onto manifold gasket)
-Clutch release bearing a little noisy
-Have never checked the timing (marks are totally inaccessable to the strobe, but the engine's running ok)
-Not sure if vacuum advance is working (nut on other side of dizzy jammed)

Many thanks.

Post by **RogerRust** » Mon Nov 07, 2005 5:29 pm

Thats very poor economy my 1098 manages 40 mpg. I suspect the timing, Its not to hard to do jack up the car a bit and get underneath with the tippex. The marks are TDC and 5 and 10 degrees of advance. turn the engine over with the handle until the points just open for cylinder 1 then get under with your torch should be about 8 degrees static.
Suck on the vacuum pipe while your looking at the points and make sure the advance works and feel the rota arm to see if the weights advance weights are moving.

If you can get underneath with the timing light watch the advance as follows.
1 tick over vacuum disconnected
2 fast idle vacuum disconnected
3 fast idle and vacuum connected
You should be able to clearly see the ignition advancing at each stage. If not you will know which bit is at fault.

Hope you have a garage.
Not the time for lying in the gutter with water running down your neck!

Good luck

Post by **rayofleamington** » Mon Nov 07, 2005 6:11 pm

My 1098 would get 20mpg when commuting in bad traffic (west midlands) - even worse in the winter due to needing the choke more and due to the oil being thicker in the cold.
It would get 30 to 35mpg on a long run A/road motorway.

Colourtune is not always an easy way to check mixture as it is hard to judge under load. You could consider to lean it off a bit more and check the plugs every few hundred miles.

Not the time for lying in the gutter with water running down your neck!

No kidding - try replacing a clutch, gearbox rear seal and crankshaft spigot bush outside in the weather we had this weekend

:brrrr:

Post by **Cam** » Mon Nov 07, 2005 6:16 pm

Ray, did the old seal just 'knock off' ok?

Post by **rayofleamington** » Mon Nov 07, 2005 6:24 pm

Ray, did the old seal just 'knock off' ok?

removed the crimped bits with an angle grinder, then tapped it off easily using hammer and blunt chisel (have done a few before)
It was cold and dark so with hindsight I should have been more careful with the grinder but I'm not well known for taking my time and being ultra careful ;-)

Post by **bmcecosse** » Mon Nov 07, 2005 7:54 pm

Colourtune is complete waste of time - set the mixture using the 'lift' pin. Almost certainly ignition timing - the vacuum advance must be working for economy - test by sucking (as said above). No need for strobe/timing marks - to get the best timing advance until it pinks - then back off very slightly till just the lightest of tinkles when putting the foot down. Also check oil in the carb damper - and is the choke going off properly ? But for town work 20/25 mpg will be normal. Even on long runs I doubt mine gets 30 mpg - but it does get hammered !

Post by **chrisd87** » Mon Nov 07, 2005 11:36 pm

Thanks for your replies!

I'll check the ignition timing and vacuum advance tomorrow. I do most of my driving around town so perhaps I shouldn't expect the economy to be too great.

Many thanks for the help.

Post by **Chris Morley** » Tue Nov 08, 2005 12:42 am

16-20 mpg is terrible unless you spend all your time in nose to tail traffic. I get higher 20s on my daily run (7 miles, two starts from cold). At a constant 60mph you should get at least 36mpg.

Post by **chrisd87** » Wed Nov 09, 2005 9:21 pm

I checked the ignition timing and vacuum advance today and it seems that both were at fault. The timing was way out (although strange given that the engine was running fine), and sucking on the vacuum pipe didn't seem to do anything.

I've put in a different dizzy, set the timing and it does seem to be running a bit smoother than it used to. I guess i'll just have to watch the fuel consumption to judge if the problem has been solved or not. The gague does tell porkies though.

I might also have a look at the manifold and carb gaskets because I think they may be leaking (oil contamination + general age).

Post by **chrisd87** » Wed Nov 09, 2005 9:31 pm

One more thing:

What oil should I use in the carb dashpot?

I had been using the rather nondescript general purpose stuff you buy in those squeezy tins from halfords, (quite thin and sort of stuff you oil doors with) but the level seems to drop very quickly (not sure if it's dropping into the carb or being pushed out the top).

I've just emptied it out and filled it with engine oil to try and solve this problem. Is this what I should be using?

Post by **Packedup** » Wed Nov 09, 2005 10:01 pm

I usually use 20/50, but I've heard people recommend ATF. I don't seem to have a problem with engine oil though. I wouldn't fancy using cheapy 3 in 1 type stuff as I'm sure it'll be way too thin.

Post by **chrisd87** » Wed Nov 09, 2005 10:12 pm

I wouldn't fancy using cheapy 3 in 1 type stuff as I'm sure it'll be way too thin.

Ooops. That's the stuff I was using! The engine oil I put in is 20W/50 so I should be OK now.

Post by **Cam** » Thu Nov 10, 2005 4:05 pm

You can buy the correct oil for the carb from Burlen, ESM and a lot of the other carb parts suppliers, but engine oil will do the job.

http://shop.morrisminorspares.co.uk/pro ... 322cae11f9

Post by **chrisd87** » Sat Nov 12, 2005 9:01 pm

Thanks everyone for their help, as the car is now using far less petrol and has better performance.

One problem follows another though - I think the clutch release bearing is now going to need replacing soon as it's making a bit of a row (a sort of growling sound) and a lot of vibration through the gear box/stick if you go over about 3000rpm.

Post by **Matt** » Sat Nov 12, 2005 9:25 pm

the clutch release bearing is basically a carbon disk. By the sound of it the carbon has all worn off! there is a rubber grommet on the undeside of the box. If you look in it with a torch you can see the bearing. There should be a step on it where the carbon is. If you cant see the steppy bit (or if its less than about 2mm) you need to replace it asap!

Post by **chrisd87** » Sat Nov 12, 2005 9:49 pm

I'll take a look at it to see if it's got really bad. I've got a new clutch kit on the way in any case, but the fitting is going to be tricky.

Would it do anything bad if I ran it with a worn bearing for a bit? What I really don't want it to do is break and jump forwards in a traffic jam!

Post by **rayofleamington** » Sat Nov 12, 2005 11:37 pm

One problem follows another though - I think the clutch release bearing is now going to need replacing soon as it's making a bit of a row (a sort of growling sound) and a lot of vibration through the gear box/stick if you go over about 3000rpm.

Just hope that you don't have the same problem that Wilberforce had - seemed like a broken/worn release bearing and was very noise and gave bad vibes on the pedal.
It turned out to be a faulty clutch cover assembly which was gradually coming unassembled and finally gave way so that one side of the clutch was permanently clamped (couldn't engage gears... RAC tow home).
The root cause was the Clutch itself. The cover is assembled with 3 release pivots which are threaded, located in nuts on the cover - the nuts are meant o be crimped to stop it coming apart but the crimping was almost non existant.
I doubt this is a one off, as there's pretty much only 1 make of 1098 clutch cover.

Post by **chrisd87** » Sat Nov 12, 2005 11:58 pm

I assume I'll have to take the gearbox off to replace the bearing so I'm going to be replacing the clutch at the same time (current one isn't particularly badly worn, but I might as well do it now). I'll take a look at the cover and see if what you've described is happening to mine too.

Funnily enough though there isn't any nasty vibration coming through the clutch pedal, but I'm pretty sure the bearing is shot given that the engine also slows down when you press the pedal on tickover, which I've heard is another symptom that the bearing is worn. I'll check it nonetheless just to make sure, as I might have to get a garage to do the work (not sure I can get the gearbox off and put it back on myself).

Post by **bigginger** » Sun Nov 13, 2005 12:22 am

It's not that hard, but I find it MUCH easier if you take the engine out as well.

Post by **Multiphonikks** » Sun Nov 13, 2005 8:47 am

rayofleamington wrote:
One problem follows another though - I think the clutch release bearing is now going to need replacing soon as it's making a bit of a row (a sort of growling sound) and a lot of vibration through the gear box/stick if you go over about 3000rpm.
Just hope that you don't have the same problem that Wilberforce had - seemed like a broken/worn release bearing and was very noise and gave bad vibes on the pedal.
It turned out to be a faulty clutch cover assembly which was gradually coming unassembled and finally gave way so that one side of the clutch was permanently clamped (couldn't engage gears... RAC tow home).
The root cause was the Clutch itself. The cover is assembled with 3 release pivots which are threaded, located in nuts on the cover - the nuts are meant o be crimped to stop it coming apart but the crimping was almost non existant.
I doubt this is a one off, as there's pretty much only 1 make of 1098 clutch cover.

Erm... Ray... That sounds scarily like the problem I've been having with Hebe - especially as the clutch is nearly new!

When the weather is better I'd better have a look