run on

Post by **grainger** » Thu Feb 13, 2003 5:18 pm

hi

run on (not stopping immediately when its switched off) is caused by overheating isnt it?

im changing the oil tomorrow - iv got the oil and filter coming from ESM - can you let me know the other things to check that may be causing it to run on ?

cheers
grainger

Post by **Cam** » Thu Feb 13, 2003 5:56 pm

Yes, pretty much.

I have had this problem for over 12 months on my 1380.

In your case it could be caused by too low an octane fuel, incorrect timing, lean mixture, tickover set too high, cooling system fault, or any of the above!!

In my case it is the high compression ratio (10:1) coupled with the fact that I have the tickover set to about 1300 RPM, because It won't tick over properly at 700-800RPM with the slightly lumpy cam that I am running.

There are a few ways to prevent it running on (apart from rectifying the above):

Buy an anti-runon valve (available from MG suppliers at about £30)

Buy a late anti-runon SU carb from a very late Metro

Open the throttle as soon as you have turned the engine off (unless you have severe run-on, in which case this will make it worse).

With the handbrake and footbrake on, let the clutch up GENTLY to drop the revs slightly as you switch off.

I have tried ALL of the above (except the carb) and the only thing that works for me is the clutch trick, because of my unnaturally high revs.

Post by **Chris Morley** » Fri Feb 14, 2003 4:04 pm

Grainger - I assume you've got a standard 1098cc? My car gets this if I run it on 95 Ron. Use the 97 ron super unleaded and the run on is less apparent. Also reduce the engine idle speed until the red ignition light glows dimly and the over-run should go. I also find these two measures increase performance slightly. Unfortunately it can make the engine a bit lumpy on cold mornings, so I increase the idle speed in Winter.

Post by **grainger** » Mon Feb 24, 2003 11:03 am

hi chris

dead right about the petrol, i filled up with shell optimax, and the run on has stopped altogether. id already dropped the tick over and that didnt seem to help. the local garage doesnt always have the optimax in so i'll have to keep me eyes open.

cheers
grainger

Post by **grainger** » Tue Feb 25, 2003 1:58 pm

... er no .. actually, this particular engine doesnt seem to like the optimax petrol and its started running rougher and running on more !! the saloon always seemed to run faster on optimax, but then it did die prematurely !!

cheers
grainger

Post by **Cam** » Tue Feb 25, 2003 4:15 pm

Try using an octane booser additive. This will reduce the run-on effect.

I currently use Shell Optimax and Castrol Valvemaster plus, which should bring my octane level to about 99/100.

I use this particular additive because I have not got hardened valve seats (no room) so I cannot run on conventional unleaded without suffering from VSR (valve seat recession).

Shell Optimax should not kill engines!! Quite the reverse, it reduces the running temperature and the likelihood of piston / valve seat erosion due to pinking caused by too low an octane level.

I have also found that my engine ran a lot smoother when I changed to optimax, the performance increased noticably, and the economy stayed about the same.

Post by **grainger** » Tue Feb 25, 2003 6:03 pm

optimax and an octane booster sounds like its worth trying, iv got to do a long run tomorrow (100mile) so i can pick some valvemaster plus before i go

but wont higher octane increase the temperature of the engine?

no sorry, i certainly dont mean optimax damaged me engine at all. as i said a few months ago i found optimax to be great for the saloon and in this one it pulls me up hills it was suffering with before, but it still sounds a little rough. i think the saloon had loose parts in the engine when i first bought it . .. so its amazing that i did 7500 miles before it gave up. now i have a little more experience

cheers
grainger

Post by **Cam** » Tue Feb 25, 2003 7:56 pm

Grainger,

Make sure you get Valvemaster Plus, as ordinary Valvemaster has not got an octane boost.

but wont higher octane increase the temperature of the engine?

No, it will run slightly cooler with a higher octane fuel, as it is less suseptable to knocking / pinking which generates excessive heat.

For a brief introduction to octane, have a look at:

http://www.howstuffworks.com/question90.htm

Good luck with your run tomorrow!

Post by **grainger** » Tue Feb 25, 2003 9:28 pm

excellent info there cam, thanks, i had heard that in the old days petrol had a higher octane rating so the cars were made to run on that obviously, but with an old engine like this wont it suffer from low compression anyway ? or is the idea of putting more octane in so it doesnt generally have to work so hard ? - i think its beginning to sink in

ill try that tomorrow anyway and let you know.

really great 'how it works' web page, thanks again

grainger

Post by **Chris Morley** » Tue Feb 25, 2003 10:27 pm

"The old days?" It's only 3 years since the old 98 octane 4-star went - even I remember putting it in my mog.

Unless your Minor's ignition has been retarded then that's probably the fuel it's happiest using.

Shell Optimax is also 98 ron, so it should be fine. Shell claims it cleans deposits off as well so maybe that's your reason for slightly rough running ?Why not have a look at your oil and see if it's suddenly gone black?

I saw an interesting documentary recently about the Battle of Britain. It showed how the Spitfire's performance was enhanced considerably when supplies of a special higher octane aviation fuel were sourced from America.

Cam - how much does Valvemaster increase the octane rating? At the moment the difference between unleaded 95 and superunleaded 97 is only 2p a litre at my local garage (sometimes it is 4p). Would a dose of valvemaster cost less per litre?

My mog seems to be going very well at the moment on superunleaded 97 and Halford's 15/50 oil.

Post by **Cam** » Wed Feb 26, 2003 12:55 am

Grainger,

When the moggy was about, there was 2-star, 3-star, 4-star and 5-star leaded petrol (before unleaded - in the UK).

I can just about remember these, when my grandad used to take me with him when he was filling up and get me a free smurf from the garage.......ah those were the days (showing my age now).

Most people used either 3-star or 4-star in family cars, with 2-star for bikes, and 5-star for sports/performance cars.

The octane levels go up depending on the star rating, and as most cars had a lower compression ratio than today, they could tolerate lower octane levels.

The problem with low compression ratios is that they do not give very good performance or economy but they make a reliable unstressed engine. As time went on and components were made stronger, the compression was raised to give more power and economy, as can be seen:

The sidevalve has a compression of only 6.5:1 compared to the 803cc A-series with 7.2:1, the 948cc A-series with 8.3:1, and finally the 1098cc A-series with 8.5:1

The older engines can tolerate a lower octane than the later ones due to the lower compression.

I have to use Shell optimax AND Valvemaster plus to give me an octane rating of about 100, because my compression ratio is just over 10:1 giving me higher performance and economy.

is the idea of putting more octane in so it doesnt generally have to work so hard ?

Actually, that's not a bad way of looking at it!

As Chris points out, the octane rating between optimax and 4-star is the same, BUT there is no valve seat protection (lead) in optimax, so unless you have an unleaded head (or have had hardened valve seats inserted) running on optimax (or any unleaded) will cause VSR (valve seat recession) so be careful!!

Chris,

Valvemaster does not increase the octane at all.
Valvemaster PLUS increases the octane by 2 points.

£9.99 buys you a bottle that treats 250 litres, so that works out at an extra 4p per litre. The main cost is for the valve seat protection properties. If you are already set up for unleaded fuel, then it's not going to be worth the extra expense and bother of putting a measured shot in every time you fill up. (twice a week for me!!).

I can't use normal unleaded and I need the extra octane, so I really have no choice, but it sounds like you might do.

Having said that, I believe you can get octane booster on it's own which should work out cheaper still, but I have not bought any, so I can't comment specifically.

Post by **grainger** » Wed Feb 26, 2003 12:13 pm

cheers for the help,

iv just got back, at least 100 miles, definately less than 10 quids worth of optimax, i couldnt get valvemaster plus so i used the redex red lead additive that i already had, (i may have overdosed that actually) and there were two of us in it ...

it was much better than a longer journey i did a few weeks ago. the run on has stopped and it pulled us reliably up hills in 3rd that i would have had to use 2nd gear with LRP, the rattling and squeaking from the springs was confusing things but overall im sure its running rougher

... when i decelerate after coasting at 50 for a while it gets a bit juddery.

possible causes i can think of,
A - like you say it might be washing some muck out (ill check me plugs)
B - i DID overdose the redex (ill put a fivers worth of optimax in without additive)
C - timing, i had it done the other week but at the time it was only running on 3 cylinders ! (dont ask

ill get it checked)
D - carb, which the guy before me says he changed the jet and washed the float chamber but im not sure he did what he said he did !! or that he knew how to do what he did do !!! but the carb seems to be in good condition, the oil (i use 3 in 1) stays in the dashpot anyway ? - but i really dont fancy messing with it, without some help at least ?!)
E - the vacuum advance isnt working, how do you check that ?
F - it needs even more octane from an additive ?

now i understand what octane is - thanks cam - when i put me foot down -because the fuel isnt being wasted going off at the wrong time, because of the compression, instead its more likely to ONLY go off when the spark hits it. octane doesnt make the petrol 'stronger' it actually inhibits its volatility under compression

.... am i right there ? cos thats what it feels like ?! - if so that really was worth learning and i will also try the valvemaster plus as soon as i can with the optimax to see if it makes it any more lively, for a fiver extra its worth a try.

cheers
grainger

Post by **grainger** » Wed Feb 26, 2003 1:23 pm

ps

i just thought of another possible cause of the rough running

G - the petrol pump ? when we had stopped at one point i noticed the pump making more noise and ticking erratically. iv already checked the fuel filter and the contacts on the pump. its always ticked every few seconds since i had it - is it worth investigating further ?

cheers
grainger

Post by **Cam** » Wed Feb 26, 2003 2:37 pm

Grainger,

I would make sure that your timing and carb are working properly before you start using the additives on a regular basis, because you might not need them, if your run-on is being caused by incorrect timing and mixture - which is VERY possible.

You may find that optimax is all that you need.

But the important question is: Is the car set up for unleaded??
you need to know this, before deciding which route to take regarding fuel and additives.

If you are planning on changing additives then you need to run out of fuel completely, as some additives don't like one another, and they recommend that once you start on one, stick to it.

A leaded car will run on unleaded fine, BUT the valve seats will erode quickly (especially at high revs) and before you know it, they will stop sealing and the seats / valve edges will burn out. - NOT good!!

octane doesnt make the petrol 'stronger' it actually inhibits its volatility under compression .... am i right there ?

Spot on, although it is more serious than wasting fuel. the flame front produced when the fuel burns (normal) is totally different than when it explodes (pinking - or dieseling) It also occurs at the wrong time and the piston recieves a strong shock in the wrong direction (against the flow) which causes the metallic tinkling pinging sound. It is also a lot hotter when it explodes or burns with the wrong mixture (lean) which can cause damage / eroded / melted components.

The reason that we have timing is so that the fuel / vapour mix is ignited just before the piston reaches the top of the bore (TDC) but it takes a short time for it to burn and produce the maximum pressure, which occurs at about 12 degrees after TDC, which is the mechanical optimum to get the most out of the power stroke.

When the engine moves faster (higher RPM), and the burn takes the same time, the mixture has to be ignited earlier to get the maximum force at 12 degrees after TDC, which is what the distributer does with its centrifugal advance unit.

The vaccum unit is there primarily for economy, and the engine will suffer no ill effects if it is not there (as long as it has not stuck in an advanced position). The engine is far more economical when the timing is advanced, BUT this can cause detonation (melting of components due to pre-ignition) if the engine is loaded and wide open throttle is used.

So, when you are decelerating or operating at partial throttle, the vaccum unit advances the timing to give you some economy, but when you put your foot down, it removes the advance so that the engine is not damaged.

You can test to see if the unit is working by using a strobeoscopic timing light and watch the timing marks (pully and pointer) when the engine is running. Disconnect the vac pipe (and plug the manifold end) then rev the engine quite high and see how far the timing marks move. This is your centrifugal advance. Then reconnect the pipe and rev again.

When you rev, when the engine is accelerating sharply there should be very little advance (centrifugal) but when it starts to decelerate under no throttle, the advance should shoot up and this is the vaccum advance reading.

If you want to test it with the car not running then take the dizzy cap off, disconnect the pipe and suck REALLY HARD. you might not be able to move it but you might just. You will see the dizzy base plate moving round (slightly) as you suck.

The petrol pump is probably OK, mine used to tick erratically, but it still worked. The fault is probably with the timing and mixture.

Post by **Chris Morley** » Wed Feb 26, 2003 4:25 pm

Cam,

I should have mentioned that I use Superblend 2000 additive, which works out between 3 and 4p a litre anyway. Perhaps I should use Castrol Valvemaster Plus when the Superblend runs out because for the same price I would get VSR protection and an octane increase.

Grainger - if your car's got a problem running on all 4 cylinders I would think that that is a big clue as to why the engine feels rough. Even a slight misfire will feel as if the engine is straining and running rough.

Don't worry about the fuel pump clicking, unless 1) it clicks very quickly, meaning you are about to run out of fuel or 2) It doesn't click at all meaning your engine is about to stop!

I find that the normal running cost is about 10p a mile for long journeys (based on 78p a litre) and I usually get 36-40 mpg depending on how heavy I am with the right foot and traffic jams.

Post by **grainger** » Wed Feb 26, 2003 9:46 pm

well i had to do another 40 miles this afternoon and its actually settling down so it might be just gunk coming through the system will it end up in me oil or stuck on my plugs ? - ill keep my eyes out, though the oil doesnt really look too dirty yet - ill get it timed again before i use an octane booster then, cheers cam.
i dont think theres any misfiring now - even at high revs - the plugs dis cap and cables are all pretty new. i was told the bloke before me had always used LRP, so ive been using unleaded with this redex lead substitute. when i couldnt get LRP and its been quite sluggish with either and prone to get hot and run on .

cheers for the help
grainger

Post by **rayofleamington** » Fri Feb 28, 2003 6:48 pm

Just being nosey, but what made you choose the Redex?

Post by **grainger** » Fri Feb 28, 2003 8:19 pm

hi ray - i only bought redex because it was the only one at the time i just kept on with it because of this point about not mixing the lead substitutes ...

i still havent been able to get it timed yet but the engine is running much smoother now, and its a lot more responsive so the optimax is getting through it. its cooler and the run on is gone altogether. i had never really noticed much pinking but it shows it must have been getting warm some how.

cheers
grainger

Post by **rayofleamington** » Sat Mar 01, 2003 3:28 pm

I thought Red-ex were one of the ones that failed the FHBC engine tests at MIRA (I may be wrong there)? If not, they failed to give samples for the tests, as I don't see them on the endorsed list.

I use Castrol Valvemaster plus for a couple of reasons (my hard driving style suits more octane and would easily damage valve seats, Castrol passed the tests and thirdly because it's easy to get at Halfords- Sunday pm etc..)

Those are just my reasons, everyone has to make their own mind up but working in automotive you get wary of any product until you know it is properly tested/proven.