N14 Celect Plus Misfire and Gray Smoke

andrewp · Dec 11, 2019

Alright guys , first of all , thanks for the inputs , I'm 99% sure we figured what's going on here .
We bypassed all the fuel system including cooling plate/check valve , fed fuel right to the pump to eliminate air or restrictions , ran a little better but was missfiring badly like before .
So at that point I had the following already replaced : injector harness , (6) injectors , (6) injector pass-thru connectors , sensor harness , Fuel shutoff solenoid , engine positioning sensor , TPS , Brand new filter and filter housing . At that point , we realized there are 2 things we did not change already : ECM and fuel pump . Decided to pull the ECM and run the truck with a test ECM , see below what we found .
Ran the truck with the test ECM , 0 issues so far , ordering a reman tomorrow . Turning the ECM upside down you could literally see corroded internal parts falling off of it . Obviously something wrong there . I'll keep you guys posted .

SpeedyGonzalez said: ↑

Same issues, the truck still sounds like it misses at idle on a cylinder but it makes great power and out pulls most trucks on some mountain passes according to the driver, hes got a pretty light foot too, and will religiously pull off at 900EGT.

We did everything driveway mechanic style because we dont have insite... yet. For us we ended up removing the check valve and running an extremely heavy initial dose of a biocide in both tanks and let the truck high idle for a few hours a day, and swapped fuel filters every other day till we stopped seeing jelly in the filters. Then we started doing 50 mile trips bobtail and checking the filters after every trip for about a week. Once we ran fuel level down far enough we pulled the saddle drains and drained the remaining fuel and washed the sides of the tank with alcohol biocide mix and let them air out for a day. Same day we had the saddles airing out we reran the overhead (no difference), inspected the camshaft with a camera. I'm still not 100% sure that the truck is in full working order, but it's been OTR continuously for a couple months now with no issues (knock on wood). The combination of the bad overhead, alage, and injectors had me going between electrical and mechanical issues, but the misfire was constant regardless of cruise or no. Basically, the algae was clogging the filter so it would run great until it drained the fuel in the filter and then it would only idle. The injectors fixed the smoking issue, and the push tubes fixed the miss at idle, although the miss at speed was most likely fuel starvation.

We checked for pin holes by pressurizing the saddles through the vent tubes to 40PSI and left if over night (unvented caps), came back the next morning and there weren't any puddles and it was at 33PSI so we assumed no holes. It being winter I'd doubt you'd see those kinds of results so I'd honestly just look for a puddle.
Then we checked fuel suction and pump pressure, both should be stable at idle, if you're sucking air you'll most likely see some fluctuation in the needle pressure side, you'd want to see about 115-130ish PSI pressure side at idle.

Our largest concern was cleaning the pick up tube screens but thankfully some engineer at KW but the saddle drain bolt directly below the pickup tubes so we were able to get them cleaned out easily, I'd imagine a pin hole in a pickup would be masked with a full tank though.
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stayinback said: ↑

Sir-Im gonna put my life on the line its the Infamous cooling plate on those N-14's........
I had a 97 9300 with an N-14- Replace the Cooling Plate- Should run like a top
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SpeedyGonzalez · Dec 11, 2019

andrewp said: ↑

Alright guys , first of all , thanks for the inputs , I'm 99% sure we figured what's going on here .
We bypassed all the fuel system including cooling plate/check valve , fed fuel right to the pump to eliminate air or restrictions , ran a little better but was missfiring badly like before .
So at that point I had the following already replaced : injector harness , (6) injectors , (6) injector pass-thru connectors , sensor harness , Fuel shutoff solenoid , engine positioning sensor , TPS , Brand new filter and filter housing . At that point , we realized there are 2 things we did not change already : ECM and fuel pump . Decided to pull the ECM and run the truck with a test ECM , see below what we found .
Ran the truck with the test ECM , 0 issues so far , ordering a reman tomorrow . Turning the ECM upside down you could literally see corroded internal parts falling off of it . Obviously something wrong there . I'll keep you guys posted .
Click to expand...

That's great you got it figured out, when you said it dissapeared with cruise on I started leaning towards ECM.

andrewp · Dec 11, 2019

The hole was in lower part of the ecm , right where it sits against the cooling plate , I'm pretty sure water and salt got inside of it and corroded internal parts and circuits , causing the missfire , maybe it affected the pedal circuit and not the cruise (I don't know if that makes any sense but it's just a thoutght) . I'll replace the ECM and cooling plate (was indeed sucking a bit of air thru the plate) and I really hope all this will be behind , this issue was driving me crazy from day 1 since I bought the truck .

DUNE-T · Sep 15, 2020

andrewp said: ↑

The hole was in lower part of the ecm , right where it sits against the cooling plate , I'm pretty sure water and salt got inside of it and corroded internal parts and circuits , causing the missfire , maybe it affected the pedal circuit and not the cruise (I don't know if that makes any sense but it's just a thoutght) . I'll replace the ECM and cooling plate (was indeed sucking a bit of air thru the plate) and I really hope all this will be behind , this issue was driving me crazy from day 1 since I bought the truck .
Click to expand...

Apparently I have the same issue. Will be replacing ecm tomorrow

CoxJuniors · Nov 28, 2020

andrewp said: ↑

The hole was in lower part of the ecm , right where it sits against the cooling plate , I'm pretty sure water and salt got inside of it and corroded internal parts and circuits , causing the missfire , maybe it affected the pedal circuit and not the cruise (I don't know if that makes any sense but it's just a thoutght) . I'll replace the ECM and cooling plate (was indeed sucking a bit of air thru the plate) and I really hope all this will be behind , this issue was driving me crazy from day 1 since I bought the truck .
Click to expand...

Hello Sr, thanks for all the great info you’ve provided! You have no clue how much you’ve helped this man. Specially in this times of tight money. I do have one petition tho, could you please come by again and confirm your problem was solved? I’m experiencing the exact same problems with my truck. And will like to know if I should just jump to replacing the ECM?

andrewp · Nov 30, 2020

The issue was solved after replacing the ECM , if I was you , I'd pull the ECM and swap it for a test ECM to see if it'll cure it . I bought the ECM from Mr. Terry from n14parts.com and I am extremely happy with how it worked out . He gave me a good price and had it rerated from 500hp to 525 for no additional cost , I'd highly recommend buying the ECM from him .

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