Help & Advice Please - Engine Misfire

[PhilR]

Hi,
I have a standard 68 1098 Traveller which has been running fine until today. At first it ran perfectly but after about 3 miles I could sense that the engine seemed to be pinking more and I seemed to have to accelerate a lot more.
As I approached a hill, the car started to pink loudly, in fact it was more of a severe top end knocking than pinking and had no power at all. I pulled in and turned the engine off.
Thinking it was ignition related I changed the plugs, leads, points condenser and the coil. This has made no difference at all. It is running rough on tick over and tries to stall. The car has absolutely no power, knocks heavily from the top end as soon as I try to accelerate. Oil and water level are perfect and no trace of any contamination. There is plenty of fuel getting to the carb too.
The symptoms are like the timing is totally out or the leads have been swapped around. This is baffling me as the car hasn't been used since last weekend and has been in a locked garage!
Could it be that the advance retard mechanism has failed in the dizzy or perhaps the dizzy itself? The dizzy was a new unit fitted two years ago.
Any help or advice would be appreciated as I am baffled by this.

[simmitc]

Check the compressions. I predict that 3&4 will be low, and your head gasket has failed between those two pots. Do not run the engine until the problem has been resolved - if I am correct, then prolonged running will wear a groove and the head and/or block, requiring major machining to fix. I might be wrong, but it sounds terribly familiar...

[mogbob]

Phil
I agree it does sound rather like timing.
Among the things you changed ...the rotor arm was not mentioned ? Do you have a spare you could try.

Note the current position of the distributer and try moving the distributer body.It shouldn't move of course but if it were loose then the symptoms might be explained.
Check the vacuum advance is working first of all though.Remove the distributer cap ( and spark plug HT leads if you like, having noted their positions ).Make sure the small spring is still attached to the base plate peg and not broken.Detach the plastic vacuum advance tube and having cleaned the end, suck on the pipe whilst observing the small movement of the base plate.
In the absence of a blocked vacuum tube, no movement at all, equals a broken vacuum advance.It's rare but not totally unheard of.Replacement of the unit, rather than the whole distributer, is possible.
Also whilst examining the distributer check the small earth tag ( low tension side ) is secure and not chafed.
Bob

[PhilR]

Thank you for you advice.
I plan to check the compression this week but thought I would check the timing side first. I did change the rotor arm and the dizzy cap but again no change. My car has a steel vacuum pipe and I did bypass it with a plastic new one but again no change.
I checked in the oil filler and coolant for signs of contamination and there was none. Furthermore there were no signs any smoke from the exhaust as I had someone follow me when I limped the car home. Of course I hope it isn't the head gasket but I have not ruled it out. The engine has only covered approx. 15k since it was a reconditioned so I guess I would be very unlucky but I guess not unheard of.
Incidentally I have been removing the small wire which goes to the dizzy of late as a security measure. I wonder if this could be the cause? I wonder if the wire has become damaged and is breaking down and this is what is causing the issue? I did give it a visible check earlier and it looked OK.
A friend has recommended that I check the valve springs in case one is broken or maybe the tappets need some adjustment. I will take a look anyway and adjust the tappets as a matter of course to rule this out. I guess this will give me the chance to have a closer look inside the rocker cover.
Also no change to petrol either. I have done at least 150 miles since I last filled it up with no previous problems.

[Pilkie]

Hi Phil.

Sounds like the dizzy has probably slipped round a few degrees!
Do you think you will make the show tomorrow?
I have decided that I will stay in the cool of my garage tomorrow and fit the engine to mine!
As the weather is gonna be hot,and I cant stand heat & sun,with no breeze!.
You are welcome to pop over to mine if it will make it,and we will see if we can sort it out.
Good luck trying to sort it.

Cheers Dave

[PhilR]

Thanks Dave.
Not going to risk tomorrow until I resolve the problem. I'm still airing on the side of timing (maybe more wishful thinking) so that's my fist port of call.
Bit disappointed that I cant attend tomorrow but will probably go with a friend in his car instead.

[bmcecosse]

It's blown the head gasket - don't run it again - sounds like you have already run it far too much and may well have burned the block and/or head. And don't waste time messing about with anything else.... Off with it's head..... Who 'reconditioned' the engine? And was the head torqued down again after the first heat cycle?? Oh and it's NEVER the coil - why on earth did you change that??

[PhilR]

I haven't changed the coil merely wired up a replacement to eliminate this as a possible cause. You say never the coil but I have experienced problems with these overheating in the past with Minors and other cars so in my opinion my logic was correct to check it and rule it out. My logic has been to eliminate as much as possible at the roadside and before going down the head gasket route.
I am going to check the static timing, advance mechanism and condition of the dizzy this week plus the valve clearances and valve springs before anything else. If anyone else has any ideas then these would be gratefully received.

[Pilkie]

Phil!
Dont assume any 1 thing is automatically THE problem!
You are correct to work your way through possible problems until you hopefully find the fault!
It may well be the headgasket,but normally you end up with water or oil loss,or it gets mixed!
When you do a compression test do it dry and wet to compare results!
Failure will be obvious!
Coils can,and do go faulty,just like condensers!
If you need any help,I am only 1/2hr away,do not hesitate,just call,even if it just for a 2nd opinion!
Right,now to pull the engine and get the replacement in.[frame][/frame]

[simmitc]

With respect to all, head gaskets on Minors normally fail between cylinders and do not mix oil and water. You have described something as happening suddenly, the engine running roughly, and loud noises. You are indeed correct to work logically through things, if fitted properly, the distributor does not just move round and upset the timing. You'll find a thread by me that recounted my problems with a very strange misfire. A compression test is quick and simple, and will remove all doubt. With both Roy and me suggesting the same thing, please do try the test - no need to repeat wet and dry, it will be obvious. If we're wrong, then we'll both be happy to admit it; but I really do believe that the best advice is to do the test before trying anything else.

[MarkyB]

You don't really need a compression tester to check for cylinders that don't fire.

Take the plugs out, spin the engine over and block each plug hole with your thumb.

A good one will just blow your thumb out of the way, a bad one will just make some kind of effort to do the same.

Just mind you don't get a belt off the HT leads if someone is using the key to turn it over.

[bmcecosse]

Exactly - as simmitic and markyb have described - the gasket blows between cylinders (1/2 or 3/4) and oil /water are not generally involved. This IS a blown head gasket - nothing else fits - my advice is to NOT run the engine - just lift the head......it only takes 30 minutes!! As others well know - when i say it's NEVER the coil - just sometimes obviously it IS the coil.....But they are extremely reliable - any overheating is due to car sitting with IGN ON and engine not running (something you should never do..) - or too tight points gap - or faulty condenser. And yes - if the coil is allowed to overheat badly - it can then fail. Modern replacement coils are often poor quality and very possibly wrong voltage (ballast ignition) and yes they will fail at any time....... But - ignore the advice if you like - it's your car and your time and effort being wasted. Even easier comp check is with the handle - turn it over and feel the cylinders.....two together will have negligible resistance........since the firing order is 2134.

[PhilR]

All advice is gratefully received and I am very appreciative that you guys have taken the time to reply. So much so I have borrowed a compression tester and will give it a go tomorrow evening.
I'll post up my findings!
Just as an aside, would a faulty low tension lead cause such problems or would that be a case of the engine not firing at all?

[bmcecosse]

Yes - poor leads and connections can obviously cause problems.....

[PhilR]

Well, I did a compression test this evening and looks like head gasket has failed between no.1 & 2 cylinders. Got a nice strong even reading from no.3 & 4 but nothing from 1 & 2.
This may be a daft question but is it typical to get a zero reading or does this suggest something more serious? I did the test on each cylinder three times and got the same readings.
So I will get the head off at the weekend but what would be your suggested course of action? I have never removed a head on my own or reground valves etc. (at times like this I wish my dad was still with us as I can recall helping him so a similar job as a teenager). Should I get it pressure tested and skimmed? Or is it more cost effective just to buy a replacement cylinder head and fit that? Also is it worth checking piston rings whilst the head is off and what is the best method for doing this?
Sorry for all the questions, just a bit shell shocked as the car was my dads pride and joy and this is the last thing I expected.

[bmcecosse]

Easy to take the head off - drain the water first...... Well detailed in the workshop manual - do you have one? If not - PM me... When the head is off - check the flatness (of both head and block) with a 12" steel rule - on edge - light behind.... Grinding in the valves is straightforward too. If you have done it before - it will soon come back to you.... But any questions - just ask! We're all here to help genuine classic car Minor folks ! When refitting - everything clean, light smear of grease on both surfaces - 'copper' gasket (local autoparts place 'head gasket for a 998 Mini please'...) and torque in stages to 44 ft lbf. Run up to temperature, and allow to cool (doesn't need to be cold) - retrorque, and set valve gaps 12 thou inlets/15 thou exhausts. Job done !

[simmitc]

As Roy says, it's a relatively simple job, but the fear of the unknown is great, and as it's your first time, just give yourself plenty of time - there is no rush. You will need the manual to get the sequence of loosening and tightening correct. There are nine head studs plus four rocker retaining studs; and they must be done in the correct order to avoid distorting the head.

So, in approximate order: Drain water. Disconnect carb and exhaust (your choice as to whether your remove the manifold from the head, or the bits from the manifold). Disconnect heater tap, top hose, and bypass hose. Remove rocker cover. Loosen nuts in correct sequence (reverse from tightening). Remove engine steady bar (secured by rear head nut). [Edit: add a couple of steps - Remove rocker gear, remove push-rods. Give each one a slight shake as you do so to make sure that the tappets or cam-followers are left in place. It is possible for them to be stuck to the rods by oil suction, and the shake breaks that.] Lift head.

When replacing, it's a reverse order. Note that the smaller rocker nuts are only 25 ft lb and not 40 - 44. Good luck, and don't hesitate to ask as you go along. Sorry I got it wrong with 3 & 4 instead of 1 & 2.

[bmcecosse]

It's a 50/50 chance 3/4 or 2/1...........

[rayofleamington]

This may be a daft question but is it typical to get a zero reading or does this suggest something more serious? I did the test on each cylinder three times and got the same readings.

There are no daft questions - only daft answers!

Yes, it's perfectly as expected to get a zero if you've got a headgasket fail between cylinders.
A lowish reading on one means there's a very slight leak (e.g. cracked ring or pitted valve)
A very low reading means a bigger leak (e.g. badly pitted valve etc..)
A zero reading means a noticeable hole (e.g. big piece of gasket missing or piston damaged or missing chunk of valve/seat.)
zero on 2 adjacent cylinders is as already expected - gasket failure between the cylinders.

On a Fiat engine I had a perfectly good compression test on all cylinders (~180 to 190psi) but there was a pinhole leak to the cooling system - thank goodness A-series engines are (normally) easy to diagnose!

[bigjim]

a few words of wisdom, always clean thoroughly , stick new gasket down with blue hylomar (rolls royce do this)i found it very successful on cars that develop oil leaks from head gasket and ALLWAYS retorque after warming up AND a week later i learnt this the hard way , i didnt use to retorque and used to go through more gaskets than morris made i think