Medium and Heavy Trucks
Have Truck Repair Questions? Ask an Expert
Hi Ron, My name is***** will be glad to help. The availability of experts varies depending on your question and the time of day you post. we can post back and forth as needed. What is the engine model and serial number? Is the check engine light on indicating there are fault codes logged? If so what codes do you have? Check for air bubbles on the suction and return side installing a clear hose or sight glass inline. Check your fuel pressure and compare to specs. Let me know
thanks for the update Ron. Is this an M11? what model engine as all your info did not post... If so there is an engine position sensor and also verify you are not loosing power to the fuel shut off solenoid signal wire from the ECM as it gets power from the ECM. The older PT systems allowed a manual bypass screw but there is none on the M11 for the fuel shutoff.
Thanks for the updated info. Lets back up as some things you mentioned stood out to me. With the key on the check engine light should come on and cycle with the key. If not your ECM has either lost power or ground, a harness problem, or other internal issues. Check for a blown inline fuse between the battery box and ECM from the battery POS post
I did not know you bypassed the fuel shutoff with direct power..... The ECM controls the throttle and fuel on this engine as well as the fuel shutoff so as far as the ECM is concerned the engine is not running if it has not powered the fuel shutoff and does not have EPS signal
Confirm the ECM is communicating first and the CEL is coming on with key on.
Then if so and the ECM has power and grounds along with switched power check for power to the fuel shutoff solenoid from the ECM. Let me know.... If all that is confirmed it is possible the EPS is faulty
You have ECM power issues and we need to correct that before this engine will run right. We need to confirm Battery power at the ECM plug is 12 V and voltage is not coming from the starter but straight from the POS of the battery.... That causes more problems on the N14 and M11 engines, etc causing low ECM power and eventually killing the ECM along with causing drivability issues from low voltage
Also take a close look at all grounds and clean and tighten the connections. There is a boor connection somewhere. If it is going to the ECM supply and is resolved after correcting then good but if the supply tests good and all grounds check good but the ECM output power is erratic then that is an indication of a bad ECM
Try the EPS and let me know
It's a pleasure to help Ron
That is always fun. Keep me posted.
See PDF pg 10
Test the power and grounds tomorrow with your volt ohm meter. The diagram is for M11 and N14 I posted... if you have power and grounds id try having the ECM bench tested and reflashed to see if it will take a reflash....
Read through this troubleshooting... It will go into more detail.... 4 hot, 3 ground, one key switched
I'm out on the road today but will have to look into this when I get back. Showing continuity to ground on those sensors? Check the harness for shorts and damage and ecm grounds....
Will it not idle? Does it stay at high RPM? Try key on press the throttle pedal to the floor slowly and back to the top 3 times to calibrate the TPS. Let me know
Check for a fuel return restriction or excessive return pressure building.
What is the year make and model of this truck?
Depends on your dealer. the dealer i worked for had test bench harnesses
Ahhhh OK.... I am not sure if I have schematics for a 94.... Keep me updated
I sent over an additional service offer for your new question. I can get you full schematics for that model to help you.
Good Morning Ron. Haha, I hear ya. I have a repair business and help on here in between jobs for some extra cash as I am able. The experts arent paid employees of the site. Credentials are verified to be able to use the site and the site splits the question value with the expert for positive feedback and accepted answers so until either our time is voluntary. So you want to ask questions about 2 trucks on one thread? Will there be three or four once I put in the time to dig through schematics, etc ? we can continue here on the M11 as needed and for the international I recommend you open a new question. I have full schematics but unless you ask for me specifically there might be another expert that helps you. You do not need to accept the additional services but the site likes to keep questions for different vehicles separate. I agree with that and understand why.
94 vintage chassis schematics for Freight liner arent easy to come by even the dealer will have to do some digging in the archives but the engine schematics I could help with.