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Voltage at Coil Terminals - Help Please
#11
I try not to appear too contrary, but for those not too expert, and using faithful analogue meters, if there is any live volts anywhere, measurement of ohms is best avoided as sooner or later volts will be encountered and wreck the meter.
Ohms Law is ohms = volts/amps and the approx amps can often be deduced from the ammeter reading.
(Analogue meters have the advantage that show erratic  connections better, less affected by igniton, dynamo  hash, other static like voltages etc,  The very cheapest good enough for old auto work,except for setting voltage regulators or otherwise checking precise battery voltages.)
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#12
(18-06-2018, 09:59 PM)Chris KC Wrote: By the way here's a checklist of 40-odd points I generated when I couldn't get my own car started. It's an excel document so heaven knows if I can attach it successfully, if not message me and I'll share it with you directly.

It took me 2 days of testing and replacing stuff to find a very slight air leak at the inlet manifold. New gasket and it started first try on the handle...

nice sheet, I've been thinking about doing one of these for a while but I think you've nailed it!
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#13
It even downloaded for me using (free) ods. Apache!
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#14
Thanks for all the advice.

I changed the lead from the coil to the distributor even though it looked OK and also found the connection to the capacitor was a bit suspect so rectified this.

Eventually I did get it to start but now it's only firing on 3 cylinders.   No 1 has a spark but with the engine running (sort of) removing the HT lead makes no difference at all.

Tomorrow I'll re-check the tappets and also try a new plug and see where that gets me.   Unfortunately I don't have a compression tester so I guess the next step would be to remove the head and look at the valves.

Out of interest what's the chance of re-using the old head gasket.   I believe it was a gasket material / copper laminate type?

John.
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#15
(20-06-2018, 04:02 AM)steve davidson Wrote:
(18-06-2018, 09:59 PM)Chris KC Wrote: By the way here's a checklist of 40-odd points I generated when I couldn't get my own car started. It's an excel document so heaven knows if I can attach it successfully, if not message me and I'll share it with you directly.

It took me 2 days of testing and replacing stuff to find a very slight air leak at the inlet manifold. New gasket and it started first try on the handle...

nice sheet, I've been thinking about doing one of these for a while but I think you've nailed it!
Thanks Steve. It of course doesn't include e.g. Zenith carbs or magneto woes, and no doubt others could add things I've not thought of. I stopped adding when I finally got the blighter to fire!

(20-06-2018, 09:09 AM)John P Wrote: Thanks for all the advice.

I changed the lead from the coil to the distributor even though it looked OK and also found the connection to the capacitor was a bit suspect so rectified this.

Eventually I did get it to start but now it's only firing on 3 cylinders.   No 1 has a spark but with the engine running (sort of) removing the HT lead makes no difference at all.

Tomorrow I'll re-check the tappets and also try a new plug and see where that gets me.   Unfortunately I don't have a compression tester so I guess the next step would be to remove the head and look at the valves.

Out of interest what's the chance of re-using the old head gasket.   I believe it was a gasket material / copper laminate type?

John.
In my experience John if the head gasket has just been fitted you can get away with re-greasing it and re-tightening. If it's an old gasket bin it and replace.
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#16
The compression tester protrudes from the radiator.  There should be a degree of similar springiness  on each cylinder.
A valve has to be very bad to cause complete misfire, perhaps stuck open. The distributor indicates which cyl. Finger over plug hole will also prove a stuck valve. All viewable, checkable  in the valve chamber, although a pain to readjust. If stuck open may  be persuaded to close with moderate pressure on something  blunt thru plug hole, or base of valve spring . if freed a few times may stay free...
When gaskets were Cu both sides and fitted dry or with a trace of grease it was normal to reuse, but modern ones dont seem to recycle well. 
If I had purchased a new gasket evry time head off my Austin and later Jowett I would now be living in a subsidised, maintained State rental with enough spare time to work on my Austin.
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#17
Nicely put Bob! In any case you need a running engine to use a compression tester properly. If it passes the thumb test it should run.
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#18
Well, I tried the finger over the plug hole compression check but I'm not sure I can tell if it's OK or not.   There certainly seems to be some compression (actually the suction on the inlet stroke is more noticeable) but I don't think it can equate to the 100 psi or so I have read would be correct.

The valves aren't sticking and although the tappets gaps were possibly slightly small I don't think it was enough to cause any issue.

I tried running the engine with the plug from the cylinder which isn't firing laying on the head.   There seems to be a good spark and the engine actually ran better with the plug out!   Presumably this is because the engine isn't doing any pumping on the missing cylinder.

So, do I bite the bullet and remove the head or buy a cheap compression tester first?   It's an Ulster replica so to lift the valves I would probably have to remove the manifolds before I could get a valve lifter in position.

John.
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#19
A very burned valve or broken rings will cause a misfire at idle but should be obvious on the handle. To miss under all conditons needs a major leakage.
Is water entering the cylinder? Is the oil milky? When running with the plug out days it eject spray? If water is being ditributed through the inlet manifold to all cyls starting would be difficult.
Fresh petrol assumed.
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#20
Nothing feels bad when I turn the engine over on the handle.

I built the engine some years ago with a re-bore, new pistons, new valves etc and it hasn't done that much mileage since.   I'm an engineer and was very careful to assemble the engine properly.

The oil is clean, there's no evidence of the water in the radiator being pressurized by a gasket failure and with the plug out there didn't seem to be anything ejected when it was running.   In fact I had expected it to be a little more dramatic but it wasn't, the engine just ran slightly better on three cylinders than with the plug in.   It doesn't seem to be a mis-fire as such, it appears that this cylinder just doesn't fire at all either at tick-over or if the engine is revved.

I feel that either one of the valves is either burned or not seating properly (although I've no idea why this would have happened) or despite there being a good spark at the plug when it's out of the engine something is breaking down when it's actually under load.   As I write I must say that also seems unlikely.   There must be fuel because the next cylinder which breaths through the same part of the inlet manifold is working OK, and this also really eliminates both ignition and cam timing.

Although I'm reluctant to start taking the engine apart when I don't know what's wrong I suppose this is the next logical step.

John.
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