hey guys, i'm still trying to nail this no start down on my truck and it seems to have a lot to do with sync. It seems that i can convince it to start if its plugged in for a few hrs prior and once it starts it runs and drives great no issues. I can even go back out 5min later and it will start up as almost normal (maybe an extra half second or so crank time sometimes not). So far I've tried cam sensor and pigtail (old one had a eaten o-ring and was leaking oil), GPCM replaced because it was throwing constant communication error code and hasn't come back. EBP sensor replaced (was reading 3psi higher than baro and map sensor). Ficm was sent to Ed to be checked out because one time i did get a hair dryer on my old one and it fired up nicely but I think that one time was a fluke because I haven't been able to duplicate that result with the hair dryer since.

ok, so where Im at now. no codes are being thrown and nothing comes up with the koeo or koer self tests when i can get it to run. I never did have any drivability issues before all this or even when I can get it to run it seems I could drive it all day without a single hiccup. An interesting thing I noticed however has to do with rpm that is being shown. I am always able to read rpm on my scanner 100% of the time and cranking speed is usually somewhere around 140rpm and it sounds like a good strong crank (i've even tried cranking while jumped up to the mrs car with same no start result when cold), however the same cannot be said about showing rpm on the dash gauge. It will stay at 0 for quite a while and only if I really stay cranking it will it jump up. What I'm wondering is if I might infact have a failing crank sensor however they rarely go bad and by plugging in the block heater its getting it all nice and toasty as if the engine was warmed up allowing it to read properly.

Far fetched I know but I'm really running out of things to check on this thing. The crank sensor ohms out at 341 and produces 140ish hz while cranking along with an AC voltage signal. Any thoughts or help would really get me down that road on this one.

Thanks guys

 

What's the sync doing? You need to watch crank and cam sync when the no start happens. You need both of those to get FICM sync or it won't start and you need 150 rpm...

Call up all 4 on the gauge and watch them, see what happens. If you get a no start, plug in and do it after it warms up, then watch again. If your using torque, data log it and then post the results.

Is it spinning easier when it's warm and you have a failing starter? 150 rpm

 

i definitely have watched both sync pids when it wouldn't start and i'm not seeing either sync. i could understand if i was getting cam/crank sync but no ficm sync that it might be a starter related issue but honestly it sounds like its spinning about as good as it ever has in the past. I'm also leaning towards the crank sensor because i've read that it is the only sensor required to establish sync at the pcm, however the more I read the more confused I get sometimes.

When it does start its as if someone threw the "ok to start switch". It doesn't roll to life struggling to start, or puff black/white smoke while trying to start. It just starts as "normal" except for the super long crank. I have also tried with the icp unplugged but I am fairly certain its not a high pressure oil issue.

I'm trying to wrap my mind around what could be temperature sensitive like this...it still takes a long crank to start off the block heater but once the engine is fully warmed up it starts pretty close to normal.

 

It's not rocket science or hard to wrap your brain around. These are numbers trucks.... easy numbers, 0 or 1. Cam and crank sync both need to be 1, they are 0 at KOEO and when you crank it, they turn to 1, unless the sensors bad or the harness is bad
Try wiggling the harness or replace the sensor., remove the connector and clean the contact points. They both need to be a 1 for FICM to be a 1. If neither go to a 1 or only one of them goes to a 1, then FICM will stay 0.
You need them to be a 1, they are not, one or both are broken.

Watch your pressure, it needs to be 500 psi or higher. ICPV NEEDS to be .80v or more. Watch fuel pulse width, it won't command fuel until everything is met.

What's a long crank? Is pressure building slow and then hit 500 and it fires? You asked for help, I'm giving the exact numbers needed to fire the truck.

 

What is your FICM voltage when you go key on and when you crank? How long have you had your unit back from FICM repair?


Ed

 

Do you have access to another FICM? Any FICM will do to try it.

 

OP I had the same issue. I did a write up last week for another similar problem but cannot find it to cut and paste. My solution was to replace the FICM power relay.


Ed

 

thanks for all the suggestions guys. look like at this point i may as well just throw a crank sensor at it, just doesn't make sense in my mind but i do understand that it only needs the 2 sensors to establish cam/crank sync.

i've only had my ficm back from Ed for a week and holds solid at 48v all of the time and logic power is always the same as batt voltage.

when cranking i'm not seeing any fpw until it actually starts and no smoke out of the tail pipe and i'm thinking that if i had a harness issue plugging in the block heater or not shouldn't make a difference.

By long crank i'd say about a good 8-10 steamboat count then it might light off. icp is showing well over 500psi and .24v koeo. ipr starts at 14.8% koeo, climbs nicely to mid 40's then settles down to 30's while cranking.

also my vref signal is strong at 5v's hopefully eliminating the possibility of a sensor short somewhere shutting down the pcm.

 

That is exactly what happened to me. Got my FICM back from Ed and things started happening. I also replaced both the crank and cam sensors. Did not solve the problem. When it would cut off I would use my X-3 tuner to clear the crank and cam codes. Then it would start and run as you described. OBTW, replacing those sensors is a very, very big PITA.

ED

 

Sorry for not saying what the fix was. I replaced the FICM power relay and all is good.


Ed