Exploder doesn't want to run!

2008 Ford Explorer 4.0L. Vehicle came in with a rattling front timing chain cassette. Another tech replaced the front cassette ONLY. Afterwards, the engine cranks, starts, and immediately stalls. Came in running. :silly:

Spark and injector pulse is present all the way to the stall. Spark is good n' strong, wire routing is correct. Feeding it carb cleaner doesn't change anything. Opening the throttle doesn't change anything.

Went in-cylinder on both banks. I need a double-check of my timing. Screenshots are taken during the highest engine speed achieved before the stall. The pressure waveform conversion is 1 mV = 1 PSI.







Can't upload the passenger bank to the forums - too big. Is it possible to downsize Pico files? I'll e-mail anyone that wants it.

Based on my limited experience using in-cylinder waveforms for timing issues, I believe the passenger side camshaft timing is late. The towers are leaning like a mofo. EVO and IVO appear late. I could be way off.

Looks like drivers bank in the screen shots has exhaust cam advanced by a couple teeth as valves opening before bdc in comparison to passenger bank.

Gotcha a Pico, huh? Nice! But, :woohoo: that's an ugly looking waveform!

Tyler wrote: Can't upload the passenger bank to the forums - too big. Is it possible to downsize Pico files?

I'll e-mail anyone that wants it.

71pole@gmail.com ...I'd like to play, when I get home. :)

Do you have a couple pulse sensors to throw in the Tail-pipe and Intake?

It's the shops, not mine. :blush: But I'm the only one that uses it, so it may as well be mine?

I'll do a relative compression with spark timing and an intake pulse before I leave tonight. Exhaust will be harder to rig up.

Chad wrote: But, :woohoo: that's an ugly looking waveform!

That'd be the Fluke PV350. I bought it five or six years ago, before I knew about the WPS500. Now I have regrets.

I was referring to the shape of the waveform. Not the tool. I have a PV-350 that I bought, used, about 10 years ago. I have no complaints with it. I have heard, though, that they started making them more cheaply a few years ago.

Is the PV-350 set to psi, or kpa?

Chad wrote: I was referring to the shape of the waveform. Not the tool. I have a PV-350 that I bought, used, about 10 years ago. I have no complaints with it. I have heard, though, that they started making them more cheaply a few years ago.

I gotcha. I found that the PV350 makes a ton of signal noise that I had to filter out with the Pico. Plus, mine won't zero out correctly anymore. :silly:

Is the PV-350 set to psi, or kpa?

PSI. For anyone following along, 1 mV = 1 PSI. I should add that to the original post...

I also got an intake waveform before I got kicked out of the shop tonight. This was taken with the injector fuse removed.

You will get, almost, 7 times the resolution if you use kpa. 1 psi=6.89 kpa
It's a little more effort to convert to psi (mV/6.89), but the waveform is much better.

Chad wrote: You will get, almost, 7 times the resolution if you use kpa. 1 psi=6.89 kpa
It's a little more effort to convert to psi (mV/6.89), but the waveform is much better.

I know, I'm just a lazy POS. :blush:

Chad wrote: You will get, almost, 7 times the resolution if you use kpa. 1 psi=6.89 kpa
It's a little more effort to convert to psi (mV/6.89), but the waveform is much better.

Should be able to do that with a custom probe. I've just thrown one together that I think should work. Put a 4 kHz low pass filter on it since Tyler's waveforms look like they need cleaning up :silly:

Change the attached files extension from zip to psprobe then import it.

Here's the passenger side.



Here is Passenger side overlayed on top of Drivers Side.

Another tech replaced the front cassette ONLY.

Are you referring to the Left bank, or the Primary Chain? Either way, the Primary had to come off. I suspect this is where the problem is? I think you need to check Cam/Crank correlation, and compare to Known Good.

This is an interference engine, too.

It looks, to me, like BOTH banks are advanced. However, the EVO looks late? :woohoo:

Early IVO




Early EVC and IVO



But, late EVO?

Chad wrote: It looks, to me, like BOTH banks are advanced. However, the EVO looks late? :woohoo:

Early IVO

I was thinking the vacuum pocket at the start of the intake stroke looked like a late IVO on both banks. And there appears to be a ~15* difference between the bottom of the pockets.

Welcome to the party, Weycraze! IVC at 15° ABDC seems a bit early, to me. I have always heard a "rule-of-thumb" IVC of 30-60° ABDC.


(Same waveform, opened with eScope.)

This is a SOHC, is it not? How can Intake timing be good (or advanced) and the Exhaust timing be late? :dry: Being an interference engine its hard to say what condition the valves are in. Although the RC and Intake waveform looked "fairly" good, with only one low vacuum pull on cylinder #3.

Matt T wrote: And there appears to be a ~15* difference between the bottom of the pockets.

I noticed that, too, But other points line up. :blink: Being a SOHC and Interference engine, I was chalking that up to valve damage. But, honestly, I don't know. I can only speculate. I hope we get to see this one through to the fix.

Chad wrote: IVC at 15° ABDC seems a bit early, to me. I have always heard a "rule-of-thumb" IVC of 30-60° ABDC.

Nevermind. :oops: Now, I see it is at 30°, not 15°.:blush:

So many replies. :woohoo: I'll catch up the best that I can.

Chad wrote: Here is Passenger side overlayed on top of Drivers Side.

Dammit Chad, quit being so awesome. You're making the rest of us look bad.

This is a SOHC, is it not? How can Intake timing be good (or advanced) and the Exhaust timing be late?

Indeed it is. Part of the problem might be trying to analyze a waveform under transient conditions (the start/stall)? I find that in-cylinder testing is best done at steady engine speeds. I can make the engine not start, but cranking in-cylinder captures are kinda useless for checking timing unless the problem is obvious.

Would there be any value in covering the throttle body during a cranking capture? Maybe make the valve events more discernable? :huh:

And there appears to be a ~15* difference between the bottom of the pockets.

That's what first caught my eye. Glad to see I was somewhat on the right track.

ForTyler.JPG

Much appreciated, Weycraze.

Are you referring to the Left bank, or the Primary Chain? Either way, the Primary had to come off. I suspect this is where the problem is?

Correct, the primary chain, left bank. Here's a visual for everyone following along:



I've never had one of these engines apart, so I'm trying to familiarize myself with the setup as I go. :silly:

I think you need to check Cam/Crank correlation, and compare to Known Good.

I have, and it's a sad story. While checking cam/crank, I discovered that the latest Snap-On update for my Triton changed saved scope capture file formats. In doing so, they also made it so negative voltages get chopped off the saved waveforms. The scope displays everything perfectly while capturing, but destroys the waveform once saved.



See what I mean? Frustrating.



The CMP pulse appears to intersect the sixth or seventh crank tooth past the sync pulse. Here's a known good courtesy of ATG and Diag.net:



Theirs is running, and appears to intersect the sixth crank pulse. So, not all that far off, unless I'm looking at it wrong.

I hope we get to see this one through to the fix.

Please. :silly: When have I not come through with a follow up?