I am hoping someone has come across this issue. My 2003 430 is making huge air pressure in the fuel tank and losing power. I believe it is combustion gases getting back to the tank and I need to run with the cap loose or the engine will stall. I have replaced all of the injectors, no help. I am thinking the air/fuel ratio line might be causing the problem so I will try to prove that next but I'm running out of ideas. Has anyone ever dealt with this type of problem please? Thank you.
is it pressure or vacuum?
Definitely pressure. When I hold my hand over the filler neck it builds enough pressure to push my hand off the fill even at idle.
is your vent on the cap plugged up?
Morning Helomaniac, If your 430 is a D model and I see your from maine im sure your machine has cold weather starting aid . its basicly a fuel nozzle (cat calls it a heater) mounted in the intake manifold It has a check valve in it that I have seen go bad which the allows boost pressure from turbo to enter fuel system. its in the intake manifold has a fuel line running to it from the fuel filter and has a wire hooked to it. looks like this. part number is 1864272 . you could take it out and plug hole see if your problem goes away . make sure to keep it hooked to fuel line and un hook wire its made to shoot flames
Thank you very much PAcattech, it is a D and from what you say I am sure you have identified my problem. I intend to plug the line tomorrow and verify the check valve failure and then replace it. I will let you know how I make out, enjoy your weekend.
I really have no first hand expert advice but i would take real good look at the injector cups and copper washers in the head. it sounds like your picking up combustion pressure into the return lines. If the motor has a looped return line on the injectors external to the motor try replacing the lines with a clear line so you can see where the air is coming from.
Thank you xcmark, that was my first thought as well. That is why I replaced all the injectors but it didn't make a dent in the problem. Since I am also losing power (boost) I believe Pacattech may have found my problem. I will give it a try tomorrow and let you all know how I make out.
Ive had this happen before, my vent was frozen.
Well here is my update. Replaced pre-heater as suggested by PAcattech. Great thought but not the problem so I disconnected the other line on the intake manifold and plugged it. This proved to be the culprit, no more pressure in the tank. Now I need to figure out why the air/fuel ratio line is doing this and what I need to replace to fix it. Unfortunately I don't have a service manual. Does anyone have any suggestions on what might make the air/fuel ratio line leak boost pressure back? Is there a check valve? Thank you.
There is a diaphragm in the air fuel ratio that is probably ripped. There is a service bulletin on this.