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Robert R
Robert R, ASE Certified Master
Category: Jeep
Satisfied Customers: 3928
Experience:  ASE Master Certified, Chrysler Certified
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Grand cherokee: 2008 jeep grand cherohkee 3.o diesel someone

Customer Question

2008 jeep grand cherohkee 3.o diesel someone put gas in it not diesel draind tank replaced filter replaced injector pump will not start unless i command the quantity sol to 60% or greater but will not start and run on its own?
Submitted: 7 months ago.
Category: Jeep
Expert:  Robert R replied 7 months ago.
Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 28+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern. The gasoline may have damaged the fuel injectors. At this time, I recommend to run an injector return flow test. If one or more injectors return excessive fuel, you will need to replace the affected injectors... How many miles on the vehicle? Will it continue to run once you get it started? Keep me posted... Thank you, Robert
Customer: replied 7 months ago.
it will only start and run while i command the quantity solenoid to 60% or greater and will only run as long as the test is ran on my scanner after that it quits
Expert:  Robert R replied 7 months ago.
That makes sense with worn out or damaged injectors. If they return too much fuel back to the tank, it makes it hard for the injection pump to make enough pressure to fire the injectors. 2000 psi is needed to fire the injectors. To run the injector return flow test, get yourself 6 pieces of clear plastic tubing just large enough to fit over the injectors with the return hoses removed. make these about 5 inches long. put all 6 tubes over the injectors and crank the engine over for a total of 30 seconds (3 - 10 second intervals). If any of them fill up the tubes, these are DEFINITELY bad, replace any that fill the tubes 1/2 of the way up or more. IF you can get it started, run the test for 60 seconds, replace any injectors that return twice as much as the one that returns the least. IF they all overflow in 60 seconds, replace ALL injectors... Keep me posted and let me know if you have any additional questions... I also need to let you know that my responses may be delayed because I may be helping another customer, or I may be temporarily offline. Your understanding is greatly appreciated. Thank you... Robert
Customer: replied 7 months ago.
actually the injector pump will not deliver any fuel via high side pressuer at all unless i do it with my scanner by commanding the quantity solenoid above 60%
Customer: replied 7 months ago.
also when i do command the quantity solenoid to 60% actuall and requested fuel pressuers at idle are 350psi they match each other
Expert:  Robert R replied 7 months ago.
How did you verify that there is no fuel output from the Injection Pump without activating the fuel quantity solenoid? 350 psi doesn't make sense for setpoint and actual fuel rail pressure with the engine running. Normal rail pressure should be around 4500 to 5000 psi at idle. Up to 20,000 psi when under heavy acceleration. What is the make and model of your scanner? Keep me posted... Thank you, Robert
Customer: replied 7 months ago.
update fguel presssuer is in bar 305 eqilvant to 4500 psi we can clamp off the fuel return hose at the injector pump and it will start and run but as soon as remove the clamp it stalls what does the pcm look for to run the quantity solnoid
Expert:  Robert R replied 7 months ago.
Ok, good, now the pressure makes more sense....LOL Have you had a chance to check the injector return flow yet? From what you are describing about pinching off the return line is in line with excessive return flow. Activating the fuel quantity solenoid is compensating for this excess return flow. There is one other thing that can caused excessive return flow, this would be the Fuel Pressure Solenoid mounted to the front of the left fuel rail. If it is bad, the left fuel rail must be replaced as an assembly.Either way, I HIGHLY recommend to start pointing your diagnostics towards finding a cause for excessive return flow... I'm posting some info on the fuel quantity solenoid for you ---> Click here. Basically the ECM uses the Fuel Quantity Solenoid along with the Fuel Pressure Solenoid to keep rail pressure at setpoint with a minimum of pressure fluctuation. Keep me posted and let me know if you have any additional questions... Thank you, Robert

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