loss of power

[andrew34ruby]

Hmm, what is this likely to be please?

The first thing I noticed was a loss of power at low revs. At high revs it still flies along at the usual 42 mph, but coming to a slight incline it wasn't happy in top gear once we had slowed to 30 mph. Usually it it is happy in fourth down to maybe 20 mph. Also it doesn't sound right at 30 or 35 in top gear.

At a fast tickover I shorted to earth each spark plug in turn. It seems cylinder number one isn't doing much. And cylinder No 2 isn't much better. Shorting out 3 or 4 slows the engine a lot, as if those cylinders are ok.

Maybe the head gasket blown between cylinders one and two?

So I did a compression test. All cylinders gave a similar reading. So not the head gasket?


Maybe just a couple of dodgy spark plugs?

["Slack Alice" Simon]

Even the slightest binding of a brake will lose you power.

I have added external springs to my fronts - the internals just wouldn't make that difference between slight rub and none at all.

[Hugh Barnes]

Random thought. Try swapping the plug positions around and see if the symptoms go with the plugs (mark them first)

[Denis Sweeney]

Just as Simon said, whilst on the Eurotour in ‘22 I had days when Ruby just flew and then out of the blue she would be sluggish.
It was not until returning home I found the Oilite bushes on the break lever cams were dry and would “seize” intermittently.
So lesson learned make sure the bushes were soaked in oil before use despite what it says on the tin.

[Ray White]

Hello Andrew. You say " it seems cylinder No 1 isn't doing much and cylinder 2 isn't much better.


Not brakes then.


The compressions are fine so your problem is probably electrical. As the weakness seems to be occurring on 1 & 2, I would be surprised is it were the points closing up so more likely to be leads or plugs.


What is a bit unusual is for more than one plug/lead to fail at the same time unless the plugs are oiling up.

Maybe see if there is a good spark from the leads. You may just need a new set of plugs.

.

[Nick Salmon]

In cases where nothing else is obvious  I have adopted a practice of putting in a full set of new spark plugs. Surprising how often it has cured the issue.

["Slack Alice" Simon]

Gosh, aren't Sevens an endless source of amusement - if you are a bit of an engineering geek, that is.

"Oilite bushes intermittently seizing"

I wonder which imp thought that one up?

Well done for spotting that.

I think I will go round with just one drop of oil on each, just in case.


Now, said imp will have to come up with something more obscure!

[Ray White]

Gosh, aren't Sevens an endless source of amusement - if you are a bit of an engineering geek, that is.

"Oilite bushes intermittently seizing"

I wonder which imp thought that one up?

Well done for spotting that.

I think I will go round with just one drop of oil on each, just in case.


Now, said imp will have to come up with something more obscure!

Surely the point of Olite bushes is that they stay lubricated as they are made of sintered bronze and impregnated with 18%. (min.) oil. However, I would ensure they had been soaked in oil overnight prior to fitting; just for good measure.

[andrew34ruby]

Random thought. Try swapping the plug positions around and see if the symptoms go with the plugs (mark them first)

Yes Hugh, the symptoms moved with the plugs. New plugs would have fixed it, but then I'd never know what was wrong with the old plugs. So I carefully examined the plugs. The electrodes end looked fine, so I did nothing there. The outer white porcelain ( the bit the world can see) looked very dirty on the worst plug, fairly dirty on the next to worst, and the 2 plugs that worked fine were fairly clean. Under load (high cylinder pressure) there was less electrical resistance through the muck than across the plug gap.

So all 4 plugs were subjected to an external clean with T-cut. A thorough clean.

And now it runs properly!

In over sixty years of repairing cars I've never come across this before. But for many years we all followed the service schedule and fitted new plugs every 12 months, and why not, at five shillings a plug.

Gleaming white plugs.
   

[Hugh Barnes]

Good to hear...