Stumped on a 6.4 no start, any help greatly appreciated!

Matt_P · Jun 4, 2016

I have a 6.4 in the shop right now that I just rebuilt the engine one. I got it all buttoned up yesterday and went to start it and once it built rail pressure it souded like it only fired on a couple of cylinders and just sat there and chugged for a couple seconds and then died. Other times it will crank and the second it is about to fire it dies immediately.

The only code I get is a P1336 cam/crank range performance. Ive tried a couple different cam and crank sensors and ohmed out all the wiring and its all good.

Rail pressure when it starts chugging gets up to 10k

All the injectors were sent out and flowed when I had the engine torn down.

The only odd thing Im seeing that is that when it starts chugging the cam and crank synchronization goes to NO when it acts like its about to die but yes when it bumps back up. but during cranking its at yes the whole time and when the rpms bump.

RPMs cranking go from 160-280

RPMs when its sitting there chugging go from 0-680

This is just a problem Ive never encountered and after 16 hours of messing with it yesterday its time to reach out so I can get this solved.

Thanks again in advance for any help!

6.0 Tech · Jun 4, 2016

Check and make sure both uvc harnesses are fully plugged into the main harness. When you built the motor did you use the correct cam timing tool?

Matt_P · Jun 4, 2016

6.0 Tech said:
Check and make sure both uvc harnesses are fully plugged into the main harness. When you built the motor did you use the correct cam timing tool?

I will check those now. Yeah I used the too, I use it on any 6.0 or 6.4 I build

Matt_P · Jun 4, 2016

uvcs are good

Matt_P · Jun 4, 2016

Bustedknuckles · Jun 4, 2016

Spray the 2 big connectors on the driver side frame rail out with contact cleaner. I had a no start with rail pressure issues caused by that. Also is your maf hooked up and your intake hooked to the turbo? I chased a no start after cab off this past week that was caused by that....

Matt_P · Jun 4, 2016

I went through and cleaned the 2 big connectors as well as every other connector and the maf is hooked up and the intake is connected to the turbo, its still doing the same thing

6.0 Tech · Jun 4, 2016

Is the egr intact? Do you have a sticking valve possibly? Is the hinge onthe pcm connector.broken? Or is the connector fully seated?

Matt_P · Jun 4, 2016

6.0 Tech said:
Is the egr intact? Do you have a sticking valve possibly? Is the hinge onthe pcm connector.broken? Or is the connector fully seated?

It's fully ******d with an aftermarket intake elbow. The hinge is in tact as well on the pcm connector and fully seated with no bent over pins or anything.

Dzchey21 · Jun 4, 2016

Does it smoke when it starts chugging? I have had several trucks with injector issues either do this or just won't run enough but they smoke like crazy and if it's really bad fuel will run out of the down pipe. I have had two trucks do this. Even if they were flowed the spool rod in the valve could stick.

sideactiondiesel · Jun 5, 2016

This a full motor build? Like cam was out ?

Matt_P · Jun 5, 2016

Dzchey21 said:
Does it smoke when it starts chugging? I have had several trucks with injector issues either do this or just won't run enough but they smoke like crazy and if it's really bad fuel will run out of the down pipe. I have had two trucks do this. Even if they were flowed the spool rod in the valve could stick.

It doesn't smoke at all during cranking or when it's chugging. Sorry I probably should have explained the chugging better. It's doesn't really start and chug it more just keeps attempting to start when it does this but the starter is still turning the engine over so it isn't fully firing. I apologize for the confusion.

sideactiondiesel said:
This a full motor build? Like cam was out ?

Yeah it was a full rebuild, cam and all was out

sideactiondiesel · Jun 5, 2016

Did the crank adapter come off as well ? Or did you leave it on cause u have the tool?
Are you sure you have the marks on and not a tooth off ? This will cause the pcm to see a crank signal to fire as long as rail pressure is met. Then looks for sync and fires. If your getting no sync and you have done all your homework on your wire harness then I am sorry but just double check this.

I mean unless your 100% like pics on your phone ?? Or something .

Matt_P · Jun 5, 2016

sideactiondiesel said:
Did the crank adapter come off as well ? Or did you leave it on cause u have the tool?
Are you sure you have the marks on and not a tooth off ? This will cause the pcm to see a crank signal to fire as long as rail pressure is met. Then looks for sync and fires. If your getting no sync and you have done all your homework on your wire harness then I am sorry but just double check this.

I mean unless your 100% like pics on your phone ?? Or something .

I actually did pull the trans yesterday and the rear cover and I popped the crank adapter off just to verify that the timing was dead on. I've never been off on timing building one before but I figured there was a first time for everything so I did all that and the timing marks are dead on. To be honest I was kinda hoping I was a tooth off so I could have at least known the problem to fix then lol

sideactiondiesel · Jun 5, 2016

I actually did pull the trans yesterday and the rear cover and I popped the crank adapter off just to verify that the timing was dead on. I've never been off on timing building one before but I figured there was a first time for everything so I did all that and the timing marks are dead on. To be honest I was kinda hoping I was a tooth off so I could have at least known the problem to fix then lol

Man I hear ya. That is frustrating to say the least. Well bring up cam and crank signal. see what one is dropping out first and go from there ...

If you will probably see the crank drop out first and then the sync will go to "no"
If so just check and make sure that CKP is all the way down in its holder. Have had some plow truck over time even swell behind sensor and cause the gap to be to far and the tone wheel can not be picked up....

Again make sure the sensor gets pulled out and you look at the hold down tab where the bolt goes in. " It will need to be strait" If not this means that sensor is not seating in the CKP bore and is causing your issue. LMK what you find

6.0 Tech · Jun 5, 2016

Is there any chance that the crank tone wheel adapter on the front of the crank got bent somehow? Or any slop in it causng it to rock on the.dowl pin? You may need to hook up an oscilloscope to monitor the cam and crank signals and make sur they are in time, or which one drops out first.

sootie · Jun 6, 2016

6.0 Tech said:
Is there any chance that the crank tone wheel adapter on the front of the crank got bent somehow? Or any slop in it causng it to rock on the.dowl pin? You may need to hook up an oscilloscope to monitor the cam and crank signals and make sur they are in time, or which one drops out first.

exactly what i was thinking. Check for a bent tone ring (cps may only be seeing it for a portion of the rotation so the signal drops out. acts like the engine is out of time), or check to make sure it is not spinning on the crank (e.g tack welds broken)

Matt_P · Jun 6, 2016

sideactiondiesel said:
Man I hear ya. That is frustrating to say the least. Well bring up cam and crank signal. see what one is dropping out first and go from there ...

If you will probably see the crank drop out first and then the sync will go to "no"
If so just check and make sure that CKP is all the way down in its holder. Have had some plow truck over time even swell behind sensor and cause the gap to be to far and the tone wheel can not be picked up....

Again make sure the sensor gets pulled out and you look at the hold down tab where the bolt goes in. " It will need to be strait" If not this means that sensor is not seating in the CKP bore and is causing your issue. LMK what you find

Yeah it's really frustrating but ill definitely double check that all again when I get back in town, thanks again for all the help!

6.0 Tech said:
Is there any chance that the crank tone wheel adapter on the front of the crank got bent somehow? Or any slop in it causng it to rock on the.dowl pin? You may need to hook up an oscilloscope to monitor the cam and crank signals and make sur they are in time, or which one drops out first.

There could always be a chance of that, I would have thought my machinist would have caught that when he had the crank on the lathe to polish it but anything is possible. I will for sure put my oscilloscope on the cam and crank sensors and monitor the signals when I get back.

sootie said:
exactly what i was thinking. Check for a bent tone ring (cps may only be seeing it for a portion of the rotation so the signal drops out. acts like the engine is out of time), or check to make sure it is not spinning on the crank (e.g tack welds broken)

It seems like it has to be something like this. I just got to the Dominican Republic for my honeymoon so I will let you guys know what I find when I get back to the shop. Thanks again!

Matt_P · Jun 13, 2016

Finally got my oscilloscope on the truck. The crank sensor does what it is supposed to do. The cam sensor does almost nothing. Ill upload a screen shot of when Im cranking on it, I cant figure out how to get a video up. It appears though that the cam sensor may be the issue. Im going to scope the cam next to see if that pin dissapeared from the cam or something