3.5 has no compression on all cylinders.

[v8440]

It will be interesting to see what caused this. I'm at a loss.

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[Spiffy]

Me too. I have built dozens of engines over 55 years and this is a first. I have experienced bent valves b4 but nothing as to cause compeat lack of compression with no apparent valve train noise when rotating under starter RPM. It rotates smooth and noise free.
I will up date.

 

[Snakebitten]

I wonder if when you pull the timing cover you see issues at the crank sprockets?

When you run the starter, does it look like the chains/phasers are traveling at the correct pace?

 

[blazef150]

I don't know what else to tell but if a engine spins over too easy and has no compression you have mutiple combustion chambers open to atmosphere. No spark plugs, few valves are sealing, Or rings are gone. Rings don't go away suddenly. If main chain jumped time and no compression there is bent valves. If cam phaser broke and disconnected from the timing chain same thing is likely. I would get a bore scope and start checking though the spark plug holes.

 

[Buyer2021]

My question is can the timing be off where the exhaust valve is not fully closing as it comes up on compression?

Not asking the right question, IMO.

If the cam rotates 360 during the cranking compression test then the non-bent exhaust valves will assuredly fully close at some point/duration during that cam rotation (bent valve-stems may prevent the valve from fully-seating).

BUT, to get compression you need both exhaust and intake valves closed concurrently at some point/duration during that 360 cam rotation.

It is possible for the cams to be off-timing so that concurrent closing never occurs (and therefore 0 compression)? Yes, IMO that is possible, it requires that the Intake and exhaust cams are not timed correctly relative to each other, even though one or the other may be timed correctly relative to the crank. It is possible that one but not both cams 'jumped the chain', or both did but different degrees.

Complete indexing of both intake and exhaust valve-trains on both banks is in order, IMO.

Just for your consideration, Good Luck.

 

[blazef150]

A broken crank usally locks the engine up that i have seen. And would usally happen under power.

 

[Spiffy]

I wonder if when you pull the timing cover you see issues at the crank sprockets?

When you run the starter, does it look like the chains/phasers are traveling at the correct pace?

Yes all the cam lifters look like they run fine. This engine doesn't have rocker arms.

 

[Spiffy]

Not asking the right question, IMO.

If the cam rotates 360 during the cranking compression test then the non-bent exhaust valves will assuredly fully close at some point/duration during that cam rotation (bent valve-stems may prevent the valve from fully-seating).

BUT, to get compression you need both exhaust and intake valves closed concurrently at some point/duration during that 360 cam rotation.

It is possible for the cams to be off-timing so that concurrent closing never occurs (and therefore 0 compression)? Yes, IMO that is possible, it requires that the Intake and exhaust cams are not timed correctly relative to each other, even though one or the other may be timed correctly relative to the crank. It is possible that one but not both cams 'jumped the chain', or both did but different degrees.

Complete indexing of both intake and exhaust valve-trains on both banks is in order, IMO.

Just for your consideration, Good Luck.

On this engine the exhaust and intake are connected with a small chain. All of the cams are turning so that rules out cam phaser disconnection. I wish I could see a graphic of the valves during each deg of rotation. I'm curious to see if there is any point where at least one valve is open in each cylinder at the same time. I doubt it will be the intake valves. I would hear that through the manifold on compression stroke.
The fact that I just drove 60 miles and heard some rattle may be that the chain at the crank had slipped enough to cause hitting of valve. But it ran good and passed a half dozen tests. The first bump of the starter sounded normal. I could hear normal compression. Then the next bump it turned really fast like I had removed the plugs. There was no loud bang that indicated I hit a valve. I would have hit 6 valves to get no compression. Bang bang bang bang bang bang. And if I had, the speed would have changed just for a moment as the piston bent a valve.

Me thinks that the chain tentioner was not applying during the starter bumps and thus the chain was loose at that exact moment and slipped on the small crank gear. There is only about 8 teeth in contact with the crank gear compared to 25 ? On the cam phaser.
I haven't had time to take the valve cover off yet. Super big job. I'm going to scope the valves. If they are bent I'm not going to fix it. If the valves are good then it has to be a stretched chain. I will replace that. If valves are bent New used engine time. Ether way I'm going to find this riddle

 

[Buyer2021]

On this engine the exhaust and intake are connected with a small chain.

Gotchya, so not a Gen 14 3.5 EB/PB with the two chains that run from crank over both cams per bank.

Good Luck with the forensics / diagnosis!

 

[Spiffy]

No a 2011. I didn't realize I was on the gen 14 site when I posted. But virtually the same engine. I also didn't know ford had changed

 

[Captain Dirty Beard]

No a 2011. I didn't realize I was on the gen 14 site when I posted. But virtually the same engine. I also didn't know ford had changed

Perhaps the crankshaft timing chain sprocket split or broke and spun on the snout of the crankshaft. This can happen if the harmonic balancer wasn't installed correctly, or the bolt not torqued properly (or a new TTY bolt was not used)

Broken Crankshaft Gear - Key Replacement? | F150 Ecoboost Forum

 

[Snakebitten]

Perhaps the crankshaft timing chain sprocket split or broke and spun on the snout of the crankshaft. This can happen if the harmonic balancer wasn't installed correctly, or the bolt not torqued properly (or a new TTY bolt was not used)

Broken Crankshaft Gear - Key Replacement? | F150 Ecoboost Forum

That's exactly what I was asking about. It's happened on Gen 3.5 Ecoboost before. (2011-2016 F150)

 

[HammaMan]

It'd take a pretty large jump in timing to develop no compression at all anywhere, and then it'd have to hold that jump in time which makes very little sense on an engine that hadn't been torn into. Need to pull the cover off and inspect the crank chain sprocket

 

[Captain Dirty Beard]

That's exactly what I was asking about. It's happened on Gen 3.5 Ecoboost before. (2011-2016 F150)

It happens on the 5.0 too, although generally when Forced induction is added, and especially PD blowers but bouncing off the rev limiter, 2 steps can do it too. If OP/shop didn't install the harmonic balancer correctly when the timing component overhaul happened, it can cause the sprocket to chatter on the crank, and split where the woodruff keyway is.

The OEM sprocket is very hard, but also brittle. That's why the Coyote guys replace them and the OPG's with billet ones. I sure did

 

[blazef150]

FYI not your exact situation but similar.

https://www.f150ecoboost.net/thread...ow-it-wont-start-documented-experience.76196/

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