Technical Starting and compression?

[jolly500]

Hi all.

I've just assembled another engine and, for the life of me, I can't get it to start. In fact I can't get any indication that it wants to start, not even a cough.
I turns over fine on a new battery and rebuilt starter.
I've had others investigate and we're all totally baffled.
I do have spark and fuel and the timing has been checked and rechecked as have the valve clearance.

So the question, as this engine has been assembled with used parts (totally against my recommendation), what influence can compression ratio have on starting?
I tested the compression and both cylinders show about 4 bar. I want to borrow another instrument to double check the readings.
Should it start with that?

Thanks
Steve...

 

[smart51]

4 bar sounds a bit low, even for a cold engine. What happens if you put a drip of oil in through the spark plug hole and repeat the test?

 

[jolly500]

4 bar sounds a bit low, even for a cold engine. What happens if you put a drip of oil in through the spark plug hole and repeat the test?

That's something I haven't tried.
Thank you, I'll give it a go...

 

[smart51]

That's something I haven't tried.
Thank you, I'll give it a go...

If you do get it running, it might be an idea to warm it up and repeat the compression test. That will give a clearer idea of the health of the engine

 

[fiat500]

Try towing it; after the usual attempt at releasing the clutch and into gear, keep towing it, in gear, slowly and steadily and see if it clears out and starts.
If nothing else, that will warm things up a bit and might give you a chance.
In the past,heating the plugs with a blowtorch and then quickly burning your fingers putting them back in has worked for me with a reluctant engine.

 

[Goldnrust]

It’s easy to overlook the little things… have you checked that you’re getting fuel to the plugs? And that you’ve not got the distributer in 180 degrees out (easily done and the timing will look right)

I wouldn't be too concerned about the compression, that main this is you have 'some'. A freshly built engine is often a bit tight, so is possibly turning a bit slower on the starter, add that the rings which are yet to bed in and you're going ot get some blow by and loss of compression.

Tow starting and hot spark plugs... have you owned a Mazda rotary in the past @fiat500 I knew people who had to do that every time their heavily ported rotors had sat for a few weeks!

 

[fiat500]

It’s easy to overlook the little things… have you checked that you’re getting fuel to the plugs? And that you’ve not got the distributer in 180 degrees out (easily done and the timing will look right)

I wouldn't be too concerned about the compression, that main this is you have 'some'. A freshly built engine is often a bit tight, so is possibly turning a bit slower on the starter, add that the rings which are yet to bed in and you're going ot get some blow by and loss of compression.

Tow starting and hot spark plugs... have you owned a Mazda rotary in the past @fiat500 I knew people who had to do that every time their heavily ported rotors had sat for a few weeks!

That's one of the many cars that it would have been good to own. But my problems have a;ways been with more sedate and straightforward engines.

It's at that point when people tell you that as long as you have a spark, fuel and compression your car will start, and you have, and it doesn't,, that more creative solutions have to be found.

 

[bugsymike]

It’s easy to overlook the little things… have you checked that you’re getting fuel to the plugs? And that you’ve not got the distributer in 180 degrees out (easily done and the timing will look right)

I wouldn't be too concerned about the compression, that main this is you have 'some'. A freshly built engine is often a bit tight, so is possibly turning a bit slower on the starter, add that the rings which are yet to bed in and you're going ot get some blow by and loss of compression.

Tow starting and hot spark plugs... have you owned a Mazda rotary in the past @fiat500 I knew people who had to do that every time their heavily ported rotors had sat for a few weeks!

Never owned a rotary Mazda, though worked at the dealers and rebuilt a couple of RX3s in the 1970s when they used a four barrel carb and two distributors with points for leading and trailing plugs etc. I probably felt my pocket wasn't deep enough, even if they kept going they were not known for fuel economy.
I did have a Mazda 1000 estate and one of the early RWD 323s.