The spill lines have a 10 bar pressure regulator in them, it's the silver cylinder at the outlet. This is needed for these pre-charged injectors.

So if the mechanicals look ok, what's causing the lost compression? Are all the valves opening and closing correctly when the cams are turned? Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Ah OK. So I shouldn't be able to suck pressure on the silver valve. So it releases pressure at 10bar?
Was hoping it was that causing the fueling issue.


Compression issue, can see the valves doing what they should while the Inlet manifold is off. Held my thumb over glow plug holes whiles cranking.. there's pressure on all 4.

Obviously I need to test once I have the m8 adapter


Put another fresh battery on today.

Even with glowplugs out. It doesn't turn over as quick as I'd expect. Added the extra earth lead.

Tidied up starter connections. And starter..

Got a amp clamp coming, guess I need to check cranking amps?

That's correct. The spill regulator only allows fuel to return to the filter if it exceeds 10 Bar. Lower pressure than 10 Bar will effect the way the injectors work, causing loss of power and misfiring.

It's strange how the load on the starter definitely reduces for 1 cylinder, which is why it speeds up for the low cylinder. It'll be interesting to see the compression pressures across the engine.

The normal cranking speed is about 250 RPM on these. Low cranking speeds will be down to an insufficiently powerful battery or failing starter contactors, which are easily replaced. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

It is strange mate.

It turned over fine until the easy start. Things fail. And they possibly have, it's just strange.
I'll check turnover rpm again tomorrow. With the fresh battery.

The amp clamp arrives tomorrow. So will check with that.

I've got a oscilloscope from a mate. But its kind of pointless going down that route yet.

Cam sensor was dirty, so I've cleaned that. Same with crank sensor and the ring.

Just don't want to fully put it back together. As if compression is poor, the head has to come off.

Amp clamp test.
12.9v fresh battery



081amps then drops off.

Not sure what the reading should be?

Injectors are out, hence the different cranking sound.

Got a m8 glowplug adapter ordered, although I could use my injector fitting I guess. Will have a look.

The starter is pulling about 1000 Watts unloaded, which is about right I would think. It's rated at around 2.2kW IIRC, so it'll likely pull that when there's some compression for it to work against. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Cheers nodge.

What should the compression be?
I've read no more then 10% difference across the cylinders, but I can't did the actual expected compression reading data.

You can work out roughly what the compression pressure will be by taking the compression ratio from the specifications, and multiplying by 14.7, which will give a rough idea of what it should be in PSI. It won't be 100% accurate, as this figure doesn't take into consideration the volumetric efficiency of the engine, but it'll be in the ballpark.
Then yes, all cylinders should be within 10% of each other. If the engine is in good health, the difference between cylinders will be under 5%. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Compression test.

1 and 4 350psi
2 and 3 230psi. Went up when oil was introduced. So rings aren't sealing it looks like.

Cylinder walls look perfect. And the valve faces look perfect.

I will obviously pull the valves to check for any damage.

Just so strange that a engine that was clean and didn't burn oil.
Suddenly does this after attempting easy start on it.

I'll attempt this on my back I guess. Pistons out the top and back in from the top with new rings on 2 and 3.

How did you find the job nodge?

As 2 cylinders with low compression are next to each other, I'd be looking at the HG for failure between them. It's very unusual for these engines to suffer piston ring wear, unless it's done huge miles.

Changing pistons in these engines isn't fun.
The sump needs removing, then the balancer shaft assembly needs to be removed, so it needs locking in place with the special tools. However for the balancer shaft assembly to be removed, the oil pump must be removed, then the block extension as the balancer shaft assembly won't come out with the block extension in place. The balancer shaft assembly is spaced away from the block with shims, so these need to be noted and fitted back in the correct place.

It's not a fun job, which needs a special toxic sealant for the sump and block extension. Also the rod caps need new bolts, and I had trouble finding the correct torque for them.

It's not a job I'd be repeating if I didn't need to. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

184k miles mate.

And was perfect and pulled like a train. Never overheated fresh service.
It's so frustrating..

At a quick glance, head gasket looked fine. And there wasn't any sign of blow by in the pots or on valve heads. But will double check.
Although that wouldn't explain the psi increasing with oil added to the pots would it?

Great lol, that does not sound fun. But I might not have any option
What special tools are required bud?

Thank you so much for your help. I can't just give up on this one as I did the last


Got a engine hoist, wondering if its easier lifting it all out. Videos I've seen, chassis lifts up over engine

184k isn't enough to wear the piston rings to the point they're letting compression past, and if it was the blow-by in the block would be noticeable.

For a pair of pistons to suddenly fail is unlikely, which just leaves the HG.
Oil will plug a gap in the HG just as easily as plugging a leaking piston ring, so it can't be ruled out.

Try spraying some WD40 into the leaking pistons, and see how long it takes to get past the rings. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Update.

Found no other issues except for the ones stated.

So, removed everything bar the block.

Replaced and lapped in valves etc, even though it looked OK.
Head gasket showed no signs of failure, so that wasn't the issue.
Oil held OK on the rings.

So.
Roughed pots 2 & 3 up. Cleaned everything up.

And put it all back together.

Got another 2nd hand fuel pump. And topped the tank up.

Apart from that, all the same.

Thankfully She fired straight up. And runs fine.



Final thoughts.

Very possible, the saddle tank has failed and when the tank is low, no fuel was being sucked from the other side of the tank.
the HP pump ran dry, possibly leading to failure.

But, there is no doubt. The easy start sprayed in by the RAC did not do the cylinders any good.

As always nodge, thanks so much for your input.

Have followed this with interest. What was the cause of the low compression on cylinders 2&3 and what was the fix.
If it was mentioned, I must have missed it. Now at the point when I learn something new something old is lost out the other side !
Now retired so it doesn't matter anymore.
Freelander now gone.

Car wouldn't start, as tank ran lower than 1/4.
Unbeknown to me, the saddle tank has failed.


I tried priming fuel through to know avail to get it going.


Called RAC to get it towed home.

Engine was cranking over normally, just not starting.

After he tried getting it to go on easy start, then towing me back.
The next morning I tried cranking it, and you could tell it had lost compression all of a sudden.

A test showed it was 2 and 3 down. Coincidentally these are the first 2 cylinders the Easy start would get to.
And it had ran the walls dry on those pots.

Hence the head was removed. Roughed up the walls, and kept turning over with oil around the rings, hoping they would reseal.

And they did. And all is fine now.

This is a rare incident. And won't be the cause of other people's issues mind.

Last edited by Jw2000uk on 13th Jun 2023 8:05 pm. Edited 1 time in total