1.6d hard to start

My caddy started getting hard to start lately when left overnight. I initially thought that it was the injector pump so rebuilt this. Then the problem persisted along with oil consumption and would not start without being towed. I done a compression test and got the following readings 300 psi, 225 psi, 175 psi, 320 psi. I then done a leak down test and the air seems to be coming up through the head so looks like the rings are gone. Is there any way to know if a new set of rings will do or if I will need to rebore?

Extremely hard to tell without having a very close look at each cylinder.

But what do you see coming out of the exhaust once it's running? 🤔
A cloud of white smoke.

What do you see on the under side of the rocker cover oil cap after the engine has been running for a while? 🤔
Something resembling white cream of just normal engine oil.

You seem to have a long list of various cars and you may have already looked at these things but it helps the members looking at your post if we clarify some things! 😉 👍🏼

Before I rebuilt the pump there was white smoke coming out of the exhaust while cranking and grey smoke for a few seconds after it started but nothing while running.
The oil in the rocker cover is just oil no water.

Well,
I would suspect that you have 2 cylinders that are needing attention.  

300psi is so-so, I thought it was to be @ 350-400

2 weak cylinders are bad, so they all need to be addressed

I have had folks with similar issues that had honed the Cylinders then replaced the rings to good success.



Was that a wet test or dry…

Second I would test your glow plugs as if you have bad ones on the good cylinders that is probably why it wouldn't start.

White smoke on start is usually condensation burning off the exhaust internally.  Gray is is oil/water burning, and if it stops then that is a sign that your rings and pistons have expanded due to engine getting to temp.

White sweet smelling exhaust is A/F burning. But you will also notice that your radiator hoses Swell…..

One quick test,
Tie a latex glove to the expansion jugs openening (take off the cap)  Tie it tight.  

Start the car, and from under the hood rev the engine to 3000 rpm for 30-45 seconds, if the glove inflates and gives you the finger, bad head gasket


Now with that said you may have cracks between the intake and exhaust valves, small cracks are normal large ones aren't.

Hi, thanks for all the info.
The compression test was done dry.
All glow plugs are relatively new and I can see them all glowing because the injectors are now removed.
I done a leak down test and there doesn't seem to be any leak into the coolant tank or through the intake/exhaust valves.
I will have to take the head off and see if the cylinders are worn. Am I right in saying that I won't see a wear lip since the pistons come up past the top of the head?
It would be good to get away with changing the rings rather than having to get it rebored.
 

I can't remember if there was a wear or crud ring when I took my head off, been too long…a time.

I would at least mic the cylinders to determine how bad they are off.,, but it could be a broken or worn ring that is all the issue is…..

It'll probably require a rebore if its using a lot of oil. But you won't know until you whip the head off. Replacing just the rings on worn bores never works in my experience. Bores don't wear evenly but go egg shaped from the thrust enforced on one side of the bore during the power stroke. Putting new round piston rings in an egg shaped bore never ends well.
Also the piston ring grooves wear and the new rings can move up and down in the groove. This causes the oil to hydraulic up past the ring and add to the oil consumption.  You need a bore guage to accurately measure the bores but you can usually get an idea by the lip where the rings come to the top of the bore. There will be a deeper lip on one side of the bore compared to the other.  

I took out the pistons today and the middle ring was broken on 2 cylinders. Hopefully a new set of rings will sort the lack of compression. There didn't seem to be too much wear on the cylinders.

I changed all the piston rings and all the seals in the head a few weeks ago. Seems to be starting great since and no smoke.