Will only start for 3-4 seconds with Cam Sensors Unplugged

I have a 2006 Mustang 4.6l 3V engine and its a swap into an old truck. I have had my harness repinned and dieted down, I have had the PCM flashed with HP tuners and have had Pats disabled.

I can sometimes get a stumble upon trying to start it but it dies. I only get one injector pulse upon first crank. Unless I unplug the cam position sensors and then I will get a fairly consistent injector pulses and it will fire up for 3-4 secs and die. Fuel pressure stays constant on the fuel regulator and fuel is present at rails. Sometimes I do here the coils continuing to fire after I release the key until I hit the key again and then it will stop. Only code I got was P0690, only with a hand hald reader but not with HP Tuners(no codes at all). I have confirmed wiring is good in on and run. Battery voltage is constant while key is cranking and when released when it fires up. Voltage maybe drops .5V when cranking and is in a good range.

I'm thinking my PCM is bad but am unsure and am hesitant to spend $500 on that unless I know for sure. My first question is why would it fire with the cam sensors unplugged? Any insight or help would be appreciated.

My set up is as follows.

All stock engine, all sensors are stock.
Manual transmission.
Stand alone fuel system with in tank pump and manual fuel pressure regulator.
Return style fuel system.
Fuel pressure set to 42psi.
I have 12V at coils in key on
I have 12V to injectors with key on.
New Ford injectors
New Spark Plugs.
New Coils.
New Cranks Sensor.
New Cam Position Sensors.
New MAF Sensor.
I have 5V reference at sensors.
I have confirmed wiring is correct at pins and have no shorts to ground.
I have confirmed good grounds.

D

What type of data pods do you have to look at? Any security data lids for the pats since it was tuned with a non ford tune. Do you have any cam sensor pics to look at? Can you scope sensors or scope not available. It’d be good if ya could screen shot some data on your scanner for us to look at

Also can you get us code setting details for the p0690 and what it means I’m not near alldata or anything for a few days

Mr Google says "When a code P0690 is stored, it means that the powertrain control module (PCM), has detected an abnormality in the relay which supplies it with voltage. This particular code will be stored if power relay sensor circuit voltage exceeds the maximum allowable parameter. The PCM power relay is used to apply battery voltage safely to the appropriate PCM circuits. It is a contact type relay that is activated with a signal wire from the ignition switch. This type of relay typically uses a five-wire design. Constant battery voltage is applied on one wire; ground on another. A third circuit carries a signal from the ignition switch and a fourth supplies voltage to the PCM. The fifth wire is the power relay sense circuit. It is used by the PCM to monitor power relay voltage.

Read more at: www.obd-codes.com/p0690
Copyright OBD-Codes.com"

darcy.mcintosh wrote: . I only get one injector pulse upon first crank. Unless I unplug the cam position sensors and then I will get a fairly consistent injector pulses and it will fire up for 3-4 secs and die.

This almost makes it sound like a CAM timing issue, if it starts with the Cam sensor unplugged.

Do you have, or can you borrow a scope. I'd sure like to see cam and crank sensor signals, along with one injector and one ignition primary signal.

Did this engine run before the swap? Have you did anything mechanical to the engine?

Cheryl wrote: Did this engine run before the swap? Have you did anything mechanical to the engine?

I have never heard it run but was told it only has 15,000km on it as they swapped in a 5.4L shelby engine and this car was only limited to summer use.

I had my mechanic friend come over and this is what we have found

1) We have no RPM while cranking,
2) We have no Cam and Crank synchronization,/correlation
3) The fuel system has been tuned with HP to be a return style and stand alone no controlled by the PCM, but the scan tool shows a fuel pump fault.
4) We have 60ohms resistance on the can bus is that correct?
5) we measure 2.5V from each canbus data line to ground. Is this correct?

Thanks Darcy

darcy.mcintosh wrote: 4) We have 60ohms resistance on the can bus is that correct?

yes

darcy.mcintosh wrote: 1) We have no RPM while cranking,
2) We have no Cam and Crank synchronization,/correlation

I'd pursue this first, as it definitely points to some kind of cam/crank signal issue.

3) The fuel system has been tuned with HP to be a return style and stand alone no controlled by the PCM, but the scan tool shows a fuel pump fault.

Sounds like the PCM software is still looking for communication with the FPDM? :huh: That by itself shouldn't cause your issue, as far as I'm aware.

4) We have 60ohms resistance on the can bus is that correct?
5) we measure 2.5V from each canbus data line to ground. Is this correct

Love it.

Did the CKP/CMP sensor wiring get changed during the swap? I've seen CKP connectors replaced due to harness damage and get the two pins swapped in the process. This causes the signal to get inverted, and the PCM can't use it. :silly: Just a thought.

A scope capture of your CKP and CMP would be best. IF you don't have one available, you can at least use a DVOM to check signal amplitude of both during cranking. Set your DVOM to AC volts and connect it across both CKP or CMP wires at the PCM. Crank it and note your highest reading. I don't have a spec on hand, but I'd expect 500mV or better. Zero is a problem.

Tyler wrote:

darcy.mcintosh wrote: 1) We have no RPM while cranking,
2) We have no Cam and Crank synchronization,/correlation

I'd pursue this first, as it definitely points to some kind of cam/crank signal issue.

3) The fuel system has been tuned with HP to be a return style and stand alone no controlled by the PCM, but the scan tool shows a fuel pump fault.

Sounds like the PCM software is still looking for communication with the FPDM? :huh: That by itself shouldn't cause your issue, as far as I'm aware.

4) We have 60ohms resistance on the can bus is that correct?
5) we measure 2.5V from each canbus data line to ground. Is this correct

Love it.

Did the CKP/CMP sensor wiring get changed during the swap? I've seen CKP connectors replaced due to harness damage and get the two pins swapped in the process. This causes the signal to get inverted, and the PCM can't use it. :silly: Just a thought.

A scope capture of your CKP and CMP would be best. IF you don't have one available, you can at least use a DVOM to check signal amplitude of both during cranking. Set your DVOM to AC volts and connect it across both CKP or CMP wires at the PCM. Crank it and note your highest reading. I don't have a spec on hand, but I'd expect 500mV or better. Zero is a problem.

This is a possibility. One thing I did notice is that sometimes when trying to start it and you stop turning it over and leave the key in the on position that you can hear the coils continue to fire. If you turn the key off or hit the key again to turn it over the condition changes.

When I back probed the CKP I only got 180mV which is low. Do you think or know if the CKP is polarity sensitive?

D

Yes, on Fords with VR crank sensors polarity matters. Get a diagram to make sure the wires are not inverted. 180 mV would be too low of a signal if this was peak to peak between the 2 wires.

juergen.scholl wrote: Yes, on Fords with VR crank sensors polarity matters. Get a diagram to make sure the wires are not inverted. 180 mV would be too low of a signal if this was peak to peak between the 2 wires.

I double checked polarity and we are good. I disconnected my CKP and connected my alligator clips and my DMM and I actually have 900mVAC while cranking, so that is good.

If I don't have an rpm signal and no cam crank correlation/synchronization, and I have also tested continuity and pinned out my cam and crank sensors wires to the PCM Harness as well as tested ohms for shorts to ground and all is good. It would almost suggest that bad PCM as it's no using the crank signal to do what it needs to.

D