Hi. Thanks for using JA! Sorry for the delay.
It sounds like you have done alot of good work so far. I know that situations like this can be very aggravating.
Since the air system from the turbo to the air to air core is good and I assume that your engine has good fuel pressure (65 tp 90 psi). There are 3 things that come to mind about your problem.
The first is the accuracy of the temperature and pressure sensors. I know that you have already replaced the atmospheric sensor, but whenever I have problem like this, I like to verify that the Boost, Intake Air temperature, fuel temperature, and atmospheric sensors are reporting accuractly when the problem is occuring on the engine. In order to do this, someone will need to have ET hooked to your engine while the porblem is occurring. I have seen sensors read way off causing the engine to have problems.
The next thing is an injector harness. I know that you have had some of the injectors replaced and well as the ECM, but I have seen the injector wiring harnesses under the valve cover cause a miss under load with no fault code.
And lastly, is the fuel supply and return lines to the engine. If they are restricted, it could cause the engine to miss. Also, problems with these lines will not show up on a DYNO because these lines are bypassed. Unless the operator runs the truck with the lines hooked up normally and not to the computer.
When your truck was run on the Dyno, did the problem happen?
Thanks for the information.
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90 to 105 is too high for a 3406E. This high pressure can be caused by 2 things.
The relief valve in the transfer pump is stuck closed, or you have a return line restriction.
If the transfer pump is the cause of the high pressure, it will not cause low power. It may however cause a fuel leak at the secondary fuel filter or the hand priming pump.
If the return fuel line of the engine is restricted, it will elevate the system pressure up to the valve opening pressure of the transfer pump. Which happens to be 105 psi. A return line restriction will cause the fuel in the head to get hotter than it should, it turn will cause low power. When the fuel stays in the head too long, it will get hot and expand and possibly aerate. These will cause your problems with your engine.
Yes. The transfer pump is located on the front of the engine.
Does your truck have a fuel pressure gauge on it? IF not, I would recommend putting one in so that when this happens, you will see if there is a fuel pressure problem.
What about the line from the engine to the tank? Has it been checked?
No problem I am glad to help.
If the problem changes like flipping a switch, it could very well be a problem with the injector harness. It may be worth trying.
Normally, if there is a return line restriction, it is fairly constant of a problem.
You are very welcome.
Thanks for the accept and bonus!