3.5 has no compression on all cylinders.

[Spiffy]

I have another truck that started to develop a very strange and loud noise up top center. Definitely not cam/chain noise. Took off valve cover. No apparent damage to can and lobes.
Went to turning enginge over with starter. There was a little snap and rotation speed speed up like there were no plugs in. No compression at all on all cylinders.
Could the chain have slipped at the crank enough to cause all cylinders to have some valve in such a position that they all are open on compression stroke?

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[tbinmd]

Best to do a compression check and I would also do a leak down. You could also check the timing marks on the cams and crank to see if they are off.

I would say it is possible the chain jumped.

 

[Spiffy]

If it has 0 compression then a leak down woukd be useless.

 

[JExpedition07]

Isn’t the 3.5 now two chains like the 5.0? One chain jumping shouldn’t effect the other bank.

 

[Spiffy]

Minecraft has one.

 

[JExpedition07]

Is this a 14th gen? I am fairly certain Ford went to 5.0 style phasers and chain setup on the 3.5 in 2021. I know older 3.5’s (gen 1) are indeed a single chain that tended to stretch and jump time at higher mileage. If this is a gen 1 engine that is a possibility.

 

[Spiffy]

I'm almost certain it's a chain issue. I don't understand how all the cylinders have no compression. Can a slipped chain cause this?
Would it have to have slipped alot?

 

[FaaWrenchBndr]

I have another truck that started to develop a very strange and loud noise up top center. Definitely not cam/chain noise. Took off valve cover. No apparent damage to can and lobes.
Went to turning enginge over with starter. There was a little snap and rotation speed speed up like there were no plugs in. No compression at all on all cylinders.
Could the chain have slipped at the crank enough to cause all cylinders to have some valve in such a position that they all are open on compression stroke?

it’s impossible that all valves would be open at the same time.

 

[blazef150]

If it's an older generation 3.5l with the single chain and you jumped time and no compression on any cylinder. Then you more than likely bent valves on multiple cylinders causing excessive leak down.

 

[v8440]

it’s impossible that all valves would be open at the same time.

Wouldn't that depend on how many valves are bent (if any), like the guy above me said? I agree that under normal conditions all valves open would be impossible.

 

[tbinmd]

What year is this truck? If it's a 14gen then both timing chains didn't slip. Maybe you dropped a value or lost a piston. How do you know you don't have compression on all cylinders. Can you turn it over my hand?

 

[Snakebitten]

On the F150, the Gen1 (long chain) 3.5 Ecoboost was 2011-2016

Gen2 3.5 was first released in the 2017 F150 with the 2 chain redesign.

Gen3 3.5 was 2021, and has the same chain design as Gen2, but with improved guides and redesigned phasers. Along with a whole host of other changes/refinements.

 

[Dizz]

No background info
Year
Mileage?

 

[Spiffy]

If it's an older generation 3.5l with the single chain and you jumped time and no compression on any cylinder. Then you more than likely bent valves on multiple cylinders causing excessive leak down.

But the truck drove 60 Miles. Then at my shop I used a diagnostic tablet. I checked compression. Power balancing, cam timing on bank a b. No dtc codes.
Truck ran perfectly fine with exception to a strange rattle.
I pulled off valve cover to inspect cam lobes, lifter faces.
Bumped starter to turn cam to look at lifers.
Bumped starter one more time. I heard some crunching from down the front of the timing chain cover and then the engine rotated fast like the were no spark plugs.
Did a starter amp draw compression test. The amp draw was flat lined. Meaning the load was consistent.

Pryor to this the truck didn't exhibit loose chain symptoms. No start up rattle. No variable timing drift on the scope. A lose chain will show drift.
So knocking out All the valves are as unlikely as the timing to be where the valves are in a position on the 720 deg rotation to be open on each cylinders compression stroke.

I know what a piston/valve strike sounds like.
Was a offshore boat racer. Built engines and had one that the piston/head clearance was so close that the expansion of the rods caused collision.
This rattle was like something bouncing around .
IF the valves were bent they would be stuck. Rotating the engine now and observing the lifters they are quite and move freely.
Or at least exhibit some kind of resistance when the cam lobes press against the lifter or in the case that the valve is stuck open the lifter woukd rattle.
I'm going to internally scope the valves later.

My question is can the timing be off where the exhaust valve is not fully closing as it comes up on compression?
If the intake is stuck open I would definitely hear it through the intake manifold. None.

 

[Spiffy]

No background info
Year
Mileage?

Sorry. 2011 3.5 ecoboost
110k miles with 10k on a complete timing, phaser overhaul.

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