2008 Ford Mustang 4.0 no start

Hey guys- need a little help here

I have a 08 ford mustang no start situation. Has already been to another shop. Got the P1000 code (no help of course). Have spark and fuel. Have good crk sensor, injector pulse. What I don't have is a good cam signal. Checked voltage at sensor and have 25mv not the 10 vdc that I should have as a bias. Checked at the PCM and not getting anything from PCM. Verified I don't have a wiring issue by disconnecting PCM and Sensor and load testing. Reconnected and installed a motorcraft cam sensor in and checked air gap and reluctor wheel. Still nothing. I do get a cam signal but it is week. I'll post it so you can see. Only peaks at .6vdc. I did a compression test of the motor and only get 75psi on all cylinders. I added oil to one cylinder thinking cylinder wash but it only came up to 80 psi. My first thought the timing is off. But that doesn't explain the weak cam signal. I am still trying to understand why have no bias voltage. Could the PCM be damaged internally not allowing bias voltage to be produced but at the same time not seeing the cam signal that is being produced? Or am I grasping at straws?
Pictures down bellow are the crank/cam and #1 injector.

Does this year offer cam/crank synchronization pid in scan data? I know newer fords do. If it’s getting fuel and spark I’d say it should run. Is the fuel contaminated?? Try running off of alternative fuel with the pump disabled. Wonder about coolant temp sensor readings and exhaust back pressure.

What’s engine rpm reading while cranking

How about doing a bypass test with test light during cranking to see if a response. If so check pcm connector. If good then pcm power and grounds before condemning the pcm.

no rpm reading

all of those test have been done. No exhaust back pressure, alternative fuel has been tried as well. No luck

May I ask where you're getting 10V bias on the cam signal from?

Can you post picture of cam and crank notch in one screen on your scope?

These are VR sensors. The cam is supposed to be supplied a 12 vdc bias voltage from the pcm.

Dave101 wrote: I do get a cam signal but it is week. I'll post it so you can see. Only peaks at .6vdc.

From ScannerDanner's "2007 FORD EXPLORER NO START, 29 VOLT FEED (PART 3) IGNITION SYSTEM OPERATION AND TESTING"
www.scannerdanner.com/scannerdanner-prem...ion-and-testing.html



Scope setup on cam was to cam+ and battery negative. It's also has peak to peak voltage of .6. Notice there's no bias voltage on the cam (ac couple was off). Is the hump count roughly the same on yours?

The crank signal and cam signal has to be good because you have spark and injector pulse. I don't know why you're not getting an rpm signal. Looking at the flow chart there's this:

Relative compression test with sync off a coil firing event - Is spark command happening at the top of a compression hump? Was your throttle plate fully opened when you took cylinder compression test? Maybe bad compression gauge? Try removing schraeder valve from it. Is the cranking speed labored? Are you using a in line spark tester? How's cranking vacuum? If the compression is really that low, where's the pressure going? Check crank case pressure at the dip stick?

Check power and grounds to coils, make sure you're not getting any voltage drop on power feed. Thinking weak spark, leads to no spark in compression stroke, leads to soaked plugs, leads to cylinder wash, leads to no start.

I'm with jreardon - the compression loss is worrying. And this wouldn't be the first 4.0L to jump time.

Vacuum gauge or in-cylinder would be my next suggestion.

So you guys think not having the 10vdc bias voltage at the cam sensor is leading me down the wrong path? I was ready to call a PCM on this vehicle because of that. Not sure as I would like to be when I call a PCM though

I would think you'd need more compression to run. I have the number 100psi in my head from somewhere as a minimum. I'm with the others who mentioned checking into that more.

Nissan Technician

Dave101 wrote: So you guys think not having the 10vdc bias voltage at the cam sensor is leading me down the wrong path? I was ready to call a PCM on this vehicle because of that. Not sure as I would like to be when I call a PCM though

Yeah, I think the cam sensor thing is a red herring. A problem, but not THE problem.

Can you post the .VSM file from your cam/crank capture?

Tyler wrote:

Dave101 wrote: So you guys think not having the 10vdc bias voltage at the cam sensor is leading me down the wrong path? I was ready to call a PCM on this vehicle because of that. Not sure as I would like to be when I call a PCM though

Yeah, I think the cam sensor thing is a red herring. A problem, but not THE problem.

Can you post the .VSM file from your cam/crank capture?

I'm going back in the morning and run a better cam/crank capture. I'll post that tomorrow. I'm also going to check the vacuum cranking pressure and more compression testing. This thing is driving me nuts.

I'm on the compression band wagon.
Hate to say it, but I think she's doomed...

I went back to it today and did the cam/crank capture. Looks to me like it may have jumped time. I will post a pic of a known good.i also did a relative compression test with ignition event on #1 cylinder. Sorry for the messy capture. I had trouble setting up the scope. Also checked the cranking vacuum. it jumped up and down 2-3 inches of vacuum. I'll go back tomorrow and do another one with the rpm hooked up. Also will do another compression test with oil. Couldn't today because of week battery. Thought??????

Looks like it jumped - 5 teeth advanced.

@30 mins in, similar waveform :

why timing chains jump in general @01:49:06:

I see the camshaft as 5-6 crank reluctor teeth retarded.

Someone double check my count, but I believe this crank reluctor has 36 teeth (missing two for the sync notch). That works out to 10 crank degrees per tooth, and thus the cam is 50 degrees retarded.

Yup 50 degrees is what i have too. retarded, advance lol i don't know, it's jumped