Technical No compression on 2 cylinders after rebuild. 1.4L Multiair

[Sean0402]

Hello all,

I have recently rebuilt my fiat 500x 1.4L Multiair Engine after finding that Cylinder 3 had very low compression and would stall on idle.

After finding the issue, I rebuilt the engine & now I have 0 compression on Cylinder 2 & 3 (The needle won't budge at all) . Cylinder 1 & 4 are perfectly fine reading around 140psi. The vehicle will start but stall almost instantly after struggling.

I have installed the following:
new piston rings on cylinder 2 & 3.
head gasket,
water pump + belt,
new intake + exhaust valves on cylinder 3,
new valve stems seals on every valve.
new spark plugs
new coil pack,
new knock sensor,
new crankshaft sensor,
new camshaft sensor,
new battery,
new multiair filter + oil filter.

I'm at a bit of a stand still as to why this is not working. My only assumption would be the piston rings as these are the only 2 things which Cylinder 2 + 3 have in common.

I have confirmed I do have spark + fuel. Also getting 0 error codes. Multiair brick seems to be operating as normal as oil is seen to be circulating through the oil cap.

 

[PuntoHowTo]

Did you have the head skimmed ? Given it’s the centre two cylinders an obvious suggestion might be a warped head.

The fact that it is so dramatically failing to provide any compression at all suggests that it should be something quite obvious? The camshaft isn’t out of phase or the valves not seating properly?

 

[Sean0402]

Did you have the head skimmed ? Given it’s the centre two cylinders an obvious suggestion might be a warped head.

The fact that it is so dramatically failing to provide any compression at all suggests that it should be something quite obvious? The camshaft isn’t out of phase or the valves not seating properly?

I have not had it skimmed. I may be inclined to take it apart and pop it into a machine shop and see what they think. The surface didn't originally look too bad but perhaps I misjudged that and looked past it. As for the timing, I have tripled checked that and it all lines up every time.

 

[s130]

Have you correctly bled the multi-air unit? There is a bleed valve inside the rocker cover directly below the oil filler aperture. This is one of those ball bearing type valves. You need to depress it whilst cranking / running the engine. Not sure for how long but suggest till no bubbles and a continuous flow emerges.

 

[bugsymike]

Have you correctly bled the multi-air unit? There is a bleed valve inside the rocker cover directly below the oil filler aperture. This is one of those ball bearing type valves. You need to depress it whilst cranking / running the engine. Not sure for how long but suggest till no bubbles and a continuous flow emerges.

Never worked on one , but reading up a bit that would be where I would start checking.
Generally speaking, any piston/ring/bore issue will still give a little compression even if bad, but if a valve is not working then instant no compression.
As the valves are hydraulically controlled , if air in system the valves cannot work as @s130 says bleeding.

 

[Sean0402]

Have you correctly bled the multi-air unit? There is a bleed valve inside the rocker cover directly below the oil filler aperture. This is one of those ball bearing type valves. You need to depress it whilst cranking / running the engine. Not sure for how long but suggest till no bubbles and a continuous flow emerges.

Never worked on one , but reading up a bit that would be where I would start checking.
Generally speaking, any piston/ring/bore issue will still give a little compression even if bad, but if a valve is not working then instant no compression.
As the valves are hydraulically controlled , if air in system the valves cannot work as @s130 says bleeding.

I’ll give this a go! Thank you!

 

[s130]

Please report back.

Unlike you I have never rebuilt a multi-air cylinder head.

I've seen videos of fancy tools to hold & secure the multi-air actuator assembly etc. and compared to my old school experience "things have changed a little"

 

[ZaphodB]

I'm so glad I didn't buy a multi-air fiat

They look like so much fun

 

[s130]

I'm so glad I didn't buy a multi-air fiat

They look like so much fun

When they work they are better than pretty good.

I have a 1000kg caravan that I have towed with a Tipo 1.6ix, Stilo Abarth 2.4, Croma 16V 2L and now a 500X Multiair 1.4L Turbo.

I can honestly say the 1.4L multiair turbo is astonishingly excellent at torque for towing and power for balls out driving.

That said when technology diverges from traditional (e.g. steam engine with huge torque but no real power) every change comes with plusses and minuses.

If you want to get more basic the old points, coil, distributor and individual plug leads whilst not up to modern ECU control incantations these old systems just work and when they go wrong are easily diagnosed and fixed.

If all else fails buy a horse and cart, shovel and hay deliveries If nothing else no road tax, no MOT, no ......

 

[348azeus]

Did you use the correct tool to lock down the Multiair unit ? If you don’t you can bend the valves. I did 4 or 5 without bending a valve but after bending two valves I now always use the tool.

 

[Sean0402]

Did you use the correct tool to lock down the Multiair unit ? If you don’t you can bend the valves. I did 4 or 5 without bending a valve but after bending two valves I now always use the tool.

I do have the special tool but I’ll have to double check the valves in the morning if this has happened :/

 

[Sean0402]

To update this thread:

I have attempted to prime the multiair brick, I now have oil flowing through the ball valve on top which is a good sign. The engine now turns over with 0 compression in any cylinders which I would assume is normal until the brick can operate the valves. I will attempt to give this more of a go tomorrow and attempt to inject oil into the valve to prime some more. I have done some research and it seems some people have had to crank is for a very long time over the course of an hour before it would even get compression.. :/