Meteor Missfire

Thats what made me think it might be the governors, one of the Scandinavian countries was the last to operate the cent, & I think a party piece of the drivers was to drive them in a manner to make the governor’s operate which created all kinds of popping & banging, in part due to the unburnt igniting in the exhaust system! although obviously that wouldn’t have applied to you.
Anyway, glad you sorted it.
any Video?
Myford

That makes sence, Plenty of unburnt fuel igniting trust me LOL:diablo:
Video here.

http://spitfirespares.com/SPITFIRESPARES.COM/pages/Spitfire%20MkVIII%20Replica%20page%203.html

right at the bottom of the page is the best one. I havent got one of it runnning properly yet ,still fixing coolant leaks.

Thats what made me think it might be the governors, one of the Scandinavian countries was the last to operate the cent, & I think a party piece of the drivers was to drive them in a manner to make the governor’s operate which created all kinds of popping & banging, in part due to the unburnt igniting in the exhaust system! although obviously that wouldn’t have applied to you.
Anyway, glad you sorted it.
any Video?
Myford

Hard to believe full power could be mistaken for idle but glad you got it sorted! ISTR suggesting you check the throttle linkage….:D

The banging and misfiring at full speed is the governers cutting the ignition. This allows unburnt fuel into the exhausts which, if hot enough, will ignite the mixture. Not good for the engine!

You would think so ,but of coarse i havent had allot of experiance running these engines and they only run to 3500 flat out nothing like a car engine, it doesnt sound like its revving hard even at full tilt. They make so much noise even on tick over its not as easy to work out as you might think.

Thanks to ISTR but i had so many things to check got to it eventually.:)

Hard to believe full power could be mistaken for idle but glad you got it sorted! ISTR suggesting you check the throttle linkage….:D

The banging and misfiring at full speed is the governers cutting the ignition. This allows unburnt fuel into the exhausts which, if hot enough, will ignite the mixture. Not good for the engine!

Problem solved

Finally got the Meteor running properly and it turned out the be the simplest of problems.
When started and running the rev counter was showing 3500 to 3750 RPM and although i worked out it should operate properly at the correct revs i just assumed that the calibration was wrong.
The throttle linkage was made up and in fact from tick over to full power without load only requires about 1 1/2 inches of movement from the throttle in the cockpit. Of coarse there is no load on the engine.
I had a look at the throttle stops and with the throttle full shut in the cockpit the carb throttles were still slightly open.
The linkage was touching the base of the carb and would not allow the throttle to close completely. I put a slight bend in the linkage so it would completely close.
The engine now starts and runs smoothly and the rev counter shows 1000 rpm, i can rev it up to about 3500 before it starts missing and backfiring.
So basically we were starting the engine at full speed and any increase in throttle without load causes missfire as its over revving.
Everytime we started it before it refused to go without some juice being put into the inlets.
It now starts without any priming, just like a car they dont like starting on full throttle.
I still need to change the inner mag covers as its not running perfectly but its 100% better than before and we are not revving its nuts off, no wonder it was heating up so quickly and using so much juice.
I want to thank all of you who contributed to this thread 🙂

troublesome Meteor

Hi Graham,
Might be worth looking at the float needles in the carburetters, just may be that the pumps are surpuling just enough fuel that she can burn but when the revs. increase so would the fuel and if the needles valves where not setting properly this would let the engine flood. I have a Allsion that we ground run and when we were learning to start her we had big troubles with the fuel system flooding and had the same problems as you are haveing I know yours has carburetters and ours an injecttion carburetteor but to me to much fuel may have the same effect on ether engine .

Just a thought from down under. Cheers Laurie.

Personally I think its the points certainly the simplest to fix first but I dont have any info on how to set them ie what gap and what position before TDC.

Thanks for all the advise all just need a bit more to hopefully solve this problem, does anyone have a Meteor manual?

While I don’t have a Meteor manual I’ve got a (shortened) reprinted manual for a Cromwell tank. An older Meteor engine probably but the following should hold for your engine:

Contact breaker gap – 0.012”

Magneto timing (no advance):

– Inlet 5° before TDC
– Exhaust 10° before TDC

Interesting that the two magnetos fire the plugs at different times. It also lists the ‘nominal governor speed’ as 2550 RPM; the maximum RPM when the ‘rev-limiters’ (on the rotor arms) cut in. With a difference of only 2000 RPM between idle and flat-out I wouldn’t have thought that a timing issue would stop the engine from revving-up, especially at such light engine loads.

I dont think its fuel starvation the plugs were soaked when i took them out and its blowing big flames when it is missfiring, the carb has plenty of juice in it.

Yes, the float chamber can be full but if a ‘power’ (as opposed to an idle) jet is blocked you can still get a very weak mixture when you open the throttle.

The duplication of the ignition system makes me think it is unlikely to be the cause of it not revving-up, you could have a few plugs or leads that are poor but I don’t think that would produce the problems that you have.

Graham Adlam wrote:

the second even a 1/4 inch of throttle is applied it missfires backfires and vibrates violenty.

Hi Graham. Don’t know if I can add positivly, but here goes.

When the engine is at idle, the two Zenith carbs are allowing fuel to mix with the air through the slow-running jets. The outlets for these are at the maximum point of manifold depression (at idle), this being near the almost closed throttle butterfly edges (all four in your case if you have retained the Zenith carbs.

If you should have any form of blockage or restriction in the carbs that would reduce or even prevent fuel flow to the main jets, you will introduce an ever increasing weak mixture when opening the throttle. One inoperative carb could also give you similar results, especially as the Zenith carbs are at each end of the ‘V’, thereby potentially giving acceptable mixture at one end of the cylinder banks, but increasingly weak at the other end.

If the mixture becomes too weak to support correct and even combustion, popping, backfiring and misfiring will result. This scenario will also result in considerable vibration (well, it is, after all 27 litres).

I suspect that your mags are fine, and a duff lead or plug would give you perceptable and uneven running, but the other eleven (or ten) cylinders will not allow one or two plugs out to generate a violent vibration.

Sorry I can’t be more helpful. Although I have been fortunate enough to work professionally on Rolls-Royce’s finest aeroengines amongst others, my knowledge of the Meteor is limited. However, a friend has asked me to help him mount one next year. If you wouldn’t mind, I would like to pick your brains deeply before I make a start on his.

In answer to some of the questions raised earlier in the thread, the Meteor does not share the Merlin method of carburation. Instead of a Skinners Union twin-choke updraft feeding into the eye of the supercharger, the Meteor which is unsupercharged, has central air intakes that feed down to a low-mounted inlet manifold that feeds to the bottom of two updraft Zenith carburettors. These are attached to either end of the upper-mounted water-heated inlet manifold that runs the length of the cylinder banks.

camlobe

I know ****** all about Metors or Merlins to be honest but something reminded me of a problem I had in the big old engine I had in my race car.

That would misfire badly when revved and it turned out to be the points. This happened after I fitted a new set so I don’t know if you have done the same?

The issue came down to the metal on the arm. The old original set had a crease in it to stiffen it but the new ones were flat. What as happening was at higher revs with thing lifting and dropping of the cam the non-creased arm was oscillating at the tip and would sometimes connect to early or not at all. This caused all sorts of misfires and a really erratic rev counter.

As soon as I put a stiffer set of points in, the problem went away.

Hi Graham, just what I was going to say!
When you open the throttle the BMEP (cylinder pressure) goes up and if you have a weak spark it becomes harder to spark through the denser mixture, but to be honest I would doubt that is the case with both mags. The centrifugal cutouts could be faulty if they are spring-loaded.
If you have not removed the mags then forget the timing base settings (and likewise with the valve timing) as it was running fine for Darren when he had it.
As far as I know there is no ign. timing adjustment on the front of the mag. If yours have two sets of points, one is fixed and the other is moveable in order to ensure they are 150° apart. This is a feature on Simms mags on the Meteor only, Merlins have one set of points.

As it is so different to the Merlin I don`t know much about the fuel system, fuel starvation, possibly along the lines of what Bruce was asking, could be an issue which would cause it to pop and bang as it goes weak.

Flames up the inlet manifold are something which any engine without a flame trap can get.

That e-mail address is not working at the moment, if you e-mail me via this forum I will get it , apologies for that!

Pete

Hello Pete

Your back, tried running her with one mag off then the other acts as it should
slight drop but still missfires like a pig when i try to throttle up. I havent adjusted the mags in any way but I took the cover off and both contacts are opening and closing. Like you said it was running fine with Darren so it cant be timing.
So you think its the plugs and leads? I only have to open the throttle a fraction and it acts up.
I dont think its fuel starvation the plugs were soaked when i took them out and its blowing big flames when it is missfiring, the carb has plenty of juice in it.
I noticed when i took the mag covers off that one of the spikes that go into the HT lead had completely rusted away so there is at least one plug not getting a spark.
Any ideas where i can get a new one from? or even new mags.
I know they can be coverted to electronic ignition but dont have a clue how to go about it?.
Thanks to all really appreciate the interest and helpfull comments.

Just had a brain wave, will run the engine with one mag on at a time this should identify problem both mags cannot have the same problem, if one is ok the missfire should vanish.:)

Hi Graham, just what I was going to say!
When you open the throttle the BMEP (cylinder pressure) goes up and if you have a weak spark it becomes harder to spark through the denser mixture, but to be honest I would doubt that is the case with both mags. The centrifugal cutouts could be faulty if they are spring-loaded.
If you have not removed the mags then forget the timing base settings (and likewise with the valve timing) as it was running fine for Darren when he had it.
As far as I know there is no ign. timing adjustment on the front of the mag. If yours have two sets of points, one is fixed and the other is moveable in order to ensure they are 150° apart. This is a feature on Simms mags on the Meteor only, Merlins have one set of points.

As it is so different to the Merlin I don`t know much about the fuel system, fuel starvation, possibly along the lines of what Bruce was asking, could be an issue which would cause it to pop and bang as it goes weak.

Flames up the inlet manifold are something which any engine without a flame trap can get.

That e-mail address is not working at the moment, if you e-mail me via this forum I will get it , apologies for that!

Pete

If the Ignition Leads are 40odd years old then they, or the plugs may be breaking down under load. Which could be why you are getting a lot of fouling on the plugs. Alternatively you could try checking the distubution caps and rotors on the mags to check for signs of shorting. Do the mags have condensers/capacitors on the points to prevent sparking at the contacts? I could be them at fault. If the meteor has an automatic Advance/Retard similar to automotive engine, is it vacuum powered? In which case there may be a leak preventing it working properly.

Just my 2ps worth

Martin

Just had a brain wave, will run the engine with one mag on at a time this should identify problem both mags cannot have the same problem, if one is ok the missfire should vanish.:)

That’s a good point(s)…..sorry. 😮 Ahhh…points…that takes me back! 🙂

Yes, check the points before you take all the plugs out! 😉 Mind you, two magnetos, at least one should be working OK. :confused:

How are the carbs and mags set up on a Meteor; presumably each magneto fires 12 plugs, six in each bank, but what about the carbs, do they feed one bank each or do all 12 cylinders draw mixture through both?

It’s tricky this duplication of everything; it makes fault finding hard…..are you sure both banks are affected?

The Meteor is set up like the Merlin, both mags drive all twelve cylinders with two sets of plugs, I guess if one mag is faulty its going to cause problems. The carb has two intakes but they also feed all 12 Cylinders, going to take off the mag covers and see how much gap opens up on the points and see if both mags are doing the same thing, one thing I noticed when cleaning the mags the points looked quite thin is this normal? . Looks like there is an advance and retard ajuster on the mags but dont want to play with this i might make it worse. I had a small fire in the carb intakes that suggests backfire to me?

I will also contact the tank experst as advised in the last couple of posts, thanks Gents

You could try contacting Bovington tank museam as they have resident mechanics on site.
They are surely the ones to ask?.
There is also one thing over looked and thats valve clearances,too tight and the valve will be held open and could cause similar symptoms.
Are they pushrod op or shim/bucket?.
Also check the operation of the floats in the carbs and possibley a compression test.

Hi Graham, use the great web to find an experienced meteor using tractor pulling team, I am sure they will have your answers.

Andy Lloyd
Napier Lion Va

Cleaned all the plugs and contacts in the mags, starts well runs smoothly on tick over, with all cylinders now firing, the second even a 1/4 inch of throttle is applied it missfires backfires and vibrates violenty.

Having read the advise here I am now pretty sure its some sort of timing problem.

There is lots of fuel and plenty of spark.

I think either the points are to close and shorting or its an ignition retarding problem. These engines are big tough and reliable I would be surprised if the ignition had a serious fault.

Personally I think its the points certainly the simplest to fix first but i dont have any info on how to set them ie what gap and what position before TDC.

Thanks for all the advise all just need a bit more to hopefully solve this problem, does anyone have a Meteor manual?

Here is the first plug to come out very sooty and has un burnt petrol on the insulator guess this ones not firing.
Here is a picture of the fuel filter one on each side, certainlky seems to flow Ok the 8 gallons we put in only lasted a few short runs

Hi graham, might sound a bit strange but do you think its possible to have either a lead or plug breaking down when they get hot. seems like you have either no ignition there or too much fuel

As in most cases its normally the simplist of problems, especially when its be running fine

It won’t help with your immediate problem but longer term are you sure the unleaded won’t attack the seals etc in the fuel system. I have heard stories from the classic car and motorcycle world of problems with melting seals etc because unleaded attacks some types of rubber, plastic, nylon etc which were quite happy to put up with leaded fuels.
As I said this won’t help with the immediate problem but may be something to consider for the future.

How are the carbs and mags set up on a Meteor; presumably each magneto fires 12 plugs, six in each bank, but what about the carbs, do they feed one bank each or do all 12 cylinders draw mixture through both?

The carbs must have different jets for idle and high revs/power…

…a silted-up ‘power’ jet could cause these symptoms…..but unlikley in both carbs at once, unless fuel supply is very dirty. :confused: