6.0 Fuel pressure question causing no start?

[GRN250]

Ok, so this seems like it’s an odd one.

What is fuel pressure while cranking? You said it dropped off after letting it set, but the pump should turn back on while cranking.

Also, what is FICM voltage, all 3 voltages, 2 should be battery voltage and one should be 48ish.

We’ve got icp, and it seems it’s trying to fire from the smoke out of the tail pipe. Are the glow plugs good? Do all injectors click good on a buzz test, none that don’t click or have a muted/dull click? Try plugging the truck in to get some heat in it if the block heater cord is installed, and see if that helps any. Leave it plugged in for 12 hours or so so it’s got plenty of time to get some heat in it.

The FICM is modified and puts out a constant 52v. The ICP has 5.06v and the cam sensor has 3.08v. Haven't checked the IPR voltage yet. The truck is currently plugged in and warming the block. Will try to start it again tomorrow.

The fuel pressure builds to 50+psi when the key is cycled but then falls off. I haven't been able to get a good video of the pressure when the key is held in the start position. The pressure does build up when the key is held in "start" but I can't say at what pressure exactly. Thanks for all the help.

 

[6.0 Tech]

The FICM is modified and puts out a constant 52v. The ICP has 5.06v and the cam sensor has 3.08v. Haven't checked the IPR voltage yet. The truck is currently plugged in and warming the block. Will try to start it again tomorrow.

The fuel pressure builds to 50+psi when the key is cycled but then falls off. I haven't been able to get a good video of the pressure when the key is held in the start position. The pressure does build up when the key is held in "start" but I can't say at what pressure exactly. Thanks for all the help.

Another thing I may have missed, and if so, I apologize. Are there any codes? I’m assuming a 314/316 codes as those tend to set from extended cranking, whether there is a problem with the cam or crank sensors or not.


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[bismic]

The cam sensor is not a v-reference sensor. Magnetically it generates its own voltage.

Also, since the PCM can "infer" an ICP pressure reading, looking at ICP sensor volts is the ONLY sure way to know what is going on with the high pressure oil pressure.

 

[GRN250]

The IPR voltage was 11.5v this morning which may be low due to my leaving the key on overnight. The truck isn't giving any codes other than EGR related; the EGR has been deleted so they are expected.

 

[6.0 Tech]

The cam sensor is not a v-reference sensor.

If I remember right though, and it doesn’t say it in the pinpoint test, is that the cmp gets its voltage from the ckp thru the pcm


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[GRN250]

The cam sensor checked out at 872 ohms which is within spec. The engine didn't start after having the block heater on for more than 12 hours. The RPMs went as high as 260 but settled at 177 and were steady for several seconds. This is slower than normal but not sure if it is below the minimum required rpm. No error codes were generated when cranked other than the standard EGR codes.

 

[bismic]

Proper cam sensor resistance is only part of the testing.

TROUBLESHOOTING CMP:

I would first check the sensor for a broken o-ring causing an oil leak into the electrical connector. Also, look for rust under the sensor flange (block rust) that could keep it furter away from the peg and prevent a strong reading.

To check the sensor: You can check the red (pin 31) and orange (pin 43) wires at the PCM center connector (C1381c). Using a multimeter that reads hertz check across both wires while cranking, you should see around 1.3 Hz (between 1.1 and 1.9 Hz is acceptable). The operating range of the sensor is .5 to 50 Hz.

Testing the sensor AND the wiring: Measure the resistance between the PCM engine connector C1381c (center plug) pin 31, harness side and the same PCM engine connector pin 43, harness side. Should be between 800 and 1000 ohms. Operating range is 800 - 11,000 ohms.

To check the WIRING ONLY: You can measure the resistance between the PCM engine connector pin 31, harness side and the CMP sensor pin 1, harness side; and between the PCM engine connector pin 43, harness side and the CMP sensor pin 2, harness side. Resistance on each test should be less than 5 ohms. CMP connector is C1275.

The CMP produces its own voltage output (AC) while the engine is cranking. Put a meter to pins 31 and 43 of the PCM plug C1381c: center PCM connector (disconnect plug from PCM - PCM is mounted outboard of drivers side battery and has 3 plug connectors). Have someone crank the engine over and check for AC voltage output of cam sensor. When checking A/C volts, the voltage will fluctuate and it should go over 0.1 volt as it fluctuates (slightly).

 

[GRN250]

Proper cam sensor resistance is only part of the testing.

TROUBLESHOOTING CMP:

I would first check the sensor for a broken o-ring causing an oil leak into the electrical connector. Also, look for rust under the sensor flange (block rust) that could keep it furter away from the peg and prevent a strong reading.

To check the sensor: You can check the red (pin 31) and orange (pin 43) wires at the PCM center connector (C1381c). Using a multimeter that reads hertz check across both wires while cranking, you should see around 1.3 Hz (between 1.1 and 1.9 Hz is acceptable). The operating range of the sensor is .5 to 50 Hz.

Testing the sensor AND the wiring: Measure the resistance between the PCM engine connector C1381c (center plug) pin 31, harness side and the same PCM engine connector pin 43, harness side. Should be between 800 and 1000 ohms. Operating range is 800 - 11,000 ohms.

To check the WIRING ONLY: You can measure the resistance between the PCM engine connector pin 31, harness side and the CMP sensor pin 1, harness side; and between the PCM engine connector pin 43, harness side and the CMP sensor pin 2, harness side. Resistance on each test should be less than 5 ohms. CMP connector is C1275.

The CMP produces its own voltage output (AC) while the engine is cranking. Put a meter to pins 31 and 43 of the PCM plug C1381c: center PCM connector (disconnect plug from PCM - PCM is mounted outboard of drivers side battery and has 3 plug connectors). Have someone crank the engine over and check for AC voltage output of cam sensor. When checking A/C volts, the voltage will fluctuate and it should go over 1 volt as it fluctuates.

The wiring has checked good when checking continuity from one end to the other with less than 5 ohms on each conductor. The wires measured 872 ohms when measuring through the sensor. Will try to measure the frequency and AC voltage tomorrow if weather permits. Thanks for your suggestions and providing the required measurement values.

 

[GRN250]

Checking between pins 43 & 31, frequency measured 1.22 but the voltage was a steady .09vac. Is this an indication the new cam sensor is bad?

 

[bismic]

Sorry! I had a typo (and corrected it above). I meant to say "over .1 volts A/C". I left the decimal point off.

You are on the cusp on the voltage, but it is probably close enough, but it SHOULD vary by at least a tenth. Not sure I understand it being completely steady - it should have a slight fluctuation.

Did you check to see if there was any rust on the block surface where the sensor mounts, or any rust on the sensor portion that is inserted?

Was it an OEM sensor?

@Maryland dieselnick asked earlier about your fuel (injector) pulse width command when cranking. Did you post that (and if so I missed it)?

 

[GRN250]

The block was clean under and around the cam sensor. The original sensor sensor was replaced with a new OEM sensor. Haven't recorded the injector pulse width yet but will try to get it later today. Thank you.

 

[bismic]

As much as I would like to point to the cam sensor, it sure doesn't appear to be the issue. Intermittent Sync has to be the cam or crank sensor, their connectors, or their wiring ....... OR an engine issue such as a bent/damaged crankshaft trigger wheel as @6.0 Tech mentioned. Pretty unlikely based in your tests. I guess a PCM issue might cause an intermittent SYNC, but that is a rare issue also.

Have you checked the crankshaft sensor wiring resistance from the PCM to the sensor? I can give you the PCM pin numbers if you need them. I guess I am thinking about the rpm drop to 177 rpm (but really there should be nothing wrong with that)

Does your PCM reported system voltage stay over 10 volts when cranking?

Do you have access to an oscilloscope?

 

[6.0 Tech]

The block was clean under and around the cam sensor. The original sensor sensor was replaced with a new OEM sensor. Haven't recorded the injector pulse width yet but will try to get it later today. Thank you.

I’m leaning towards you may need to get an oscilloscope on it. Verify everything looks good on that.

Could still be ckp wiring though.

Well shit, bismic beat me to it. Guess I should’ve kept scrolling down…


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[GRN250]

As much as I would like to point to the cam sensor, it sure doesn't appear to be the issue. Intermittent Sync has to be the cam or crank sensor, their connectors, or their wiring ....... OR an engine issue such as a bent/damaged crankshaft trigger wheel as @6.0 Tech mentioned. Pretty unlikely based in your tests. I guess a PCM issue might cause an intermittent SYNC, but that is a rare issue also.

Have you checked the crankshaft sensor wiring resistance from the PCM to the sensor? I can give you the PCM pin numbers if you need them. I guess I am thinking about the rpm drop to 177 rpm (but really there should be nothing wrong with that)

Does your PCM reported system voltage stay over 10 volts when cranking?

Do you have access to an oscilloscope?

I have not checked the Crank sensor wiring to the PCM plug yet. The voltage is staying above 10v while cranking and I am leaving a battery charger/booster connected to make sure the starter gets steady voltage. I don't have access to an oscilloscope.

Attempted to get the injector pulse width but am not sure what option to use with AutoEnginuity. Would it be the "injector timing"? I was looking for an individual "event" for each injector but don't see an option. Tonight the PCM did give two new errors. P2552 Throttle/fuel inhibit circuit/open and B1359 Ignition run/accessory Circuit Failure.

 

[bismic]

P2552: FICM M Circuit - Throttle/Fuel Inhibit Circuit: Power Monitor Activated. No signal from the FICM Monitor circuit. FICM or PCM open/short. Could be from a FICM plug (usually middle plug) not firmly seated. Could also be from an injector connector pin bent (if you also have an injector "circuit low" code).

Check that middle FICM plug and its pins!

 

[GRN250]

The P2552 error cleared today without touching the FICM. The plugs are locked in place. I ran the KOEO test and it passed again and the Injector buzz test said it completed successfully but only three of the eight injectors actually buzzed this time; the other five injectors just clicked. The connections are tight with the locking clips in place and a new, OEM harness was installed when the heads/head studs were installed. Not sure what has changed but considering pulling the injectors and having them tested. I previously had the FICM repaired; could it have damaged the injectors prior to having it repaired?

Still planning on checking the crank sensor wiring when I get some longer meter leads. Feel like I am chasing a moving target with the symptoms changing and previously passed tests failing when retested. Beginning to think there are multiple problems at hand.

 

[6.0 Tech]

The P2552 error cleared today without touching the FICM. The plugs are locked in place. I ran the KOEO test and it passed again and the Injector buzz test said it completed successfully but only three of the eight injectors actually buzzed this time; the other five injectors just clicked. The connections are tight with the locking clips in place and a new, OEM harness was installed when the heads/head studs were installed. Not sure what has changed but considering pulling the injectors and having them tested. I previously had the FICM repaired; could it have damaged the injectors prior to having it repaired?

Still planning on checking the crank sensor wiring when I get some longer meter leads. Feel like I am chasing a moving target with the symptoms changing and previously passed tests failing when retested. Beginning to think there are multiple problems at hand.

Not sure how what software you’re using does the buzz test, but typically it will batch fire the injectors, like if you had just turned the key on, then each one clicks in cylinder number order. Typically a good injector has a solid/sharp click, sometimes there will be a dull/muted click, which indicates the spool valve is moving, just not as well as it should, or no click at all, which indicates the spool valve has an issue. If you’ve only got 3 that are doing what they’re supposed to, an injector issue is likely.


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[GRN250]

Not sure how what software you’re using does the buzz test, but typically it will batch fire the injectors, like if you had just turned the key on, then each one clicks in cylinder number order. Typically a good injector has a solid/sharp click, sometimes there will be a dull/muted click, which indicates the spool valve is moving, just not as well as it should, or no click at all, which indicates the spool valve has an issue. If you’ve only got 3 that are doing what they’re supposed to, an injector issue is likely.


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All the injectors have a defined click but three have a buzz sound. The buzz sound is what I am accustomed to hearing on my 7.3 injectors during a buzz test. The AE software indicates the test passes. It could be I am comparing two engine injector sounds that are nothing alike.

 

[bismic]

I don't see the injector concerns you have as causing a no-start.

I have to agree that it MIGHT be several things at once. That said, I would probably send the FICM off and have it tested.

 

[6.0 Tech]

All the injectors have a defined click but three have a buzz sound. The buzz sound is what I am accustomed to hearing on my 7.3 injectors during a buzz test. The AE software indicates the test passes. It could be I am comparing two engine injector sounds that are nothing alike.

So if 3 buzz, and the other 5 are a nice solid click, I’d say there is probably an issue with those 3 or the FICM, but as bismic said, I don’t think 3 injectors having an issue would cause the no start, unless it was in the FICM. Try unplugging the 3 that buzzed and see what happens.


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